ArticlePDF AvailableLiterature Review

Biological and clinical aspects in laser hair removal

  • EndyMed Medical
  • elman medial clinics israel

Abstract and Figures

In the past century, unwanted hair has been traditionally treated with multitudes of techniques that were found to be slow, tedious, painful, impractical, and resulted in poor long-term efficacy. Consequently, there has been a public demand for a novel, rapid, reliable, safe, and affordable hair removal technique. In the last decade, laser and light-based technology for hair removal became one of the fastest growing procedures in modern cosmetic dermatology. To discuss the latest scientific and clinical issues in the field of photoepilation as evolved in the past decade: hair biology, laser physics and skin optics, technology and clinical experience. From substantial clinical experience, it becomes apparent that in the ideal subject with fair skin and dark hair, a single treatment can reduce hair by 10-40%; three treatments by 30-70%; and repeated treatments by as much as 90%. These results persist for as long as 12 months. Diffuse and perifollicular cutaneous erythema and pigmentary changes are the most common adverse side effects. Most complications are generally temporary. Photoepilation, when properly used, offers clear advantages when compared with older, traditional techniques. Although an ever-increasing number of published studies have confirmed the safety and short and long-term efficacy of photoepilation, the technology still has limits and risks.
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Biological and clinical aspects in laser hair removal
Excess hair and/or unwanted hair are of significant
medical, social and cultural importance and are there-
fore the subject of much attention, manipulation and
regard in both genders and all races. The multitude
of treatments available is testimony to these facts.
Traditionally, conditions such as hirsutism, hypertri-
chosis, and cosmetic elegance have been treated with
electrolysis/thermolysis, tweezing, shaving, waxing and
sugaring, plucking, threading, depilatories and X-ray
These methods, however, were found to be
slow, tedious, painful, impractical for treating large
areas, and, in most cases, temporary. Consequently, the
need for a long-term, non-invasive, rapid, reliable and
safe method became a necessity in our society.
When first described some 7 years ago, laser hair
removal created controversy.
As the technology
matured, laser hair removal generated growing
demand not only for a safe, non-invasive, pain-free
procedure, but also for effective, rapid pace, easy to
operate, and affordable technology. Today, photoepila-
tion by laser and other light-based technology is the
fastest growing procedure in modern cosmetic derma-
tology. As more clinical research and experience is
gained in the field of laser hair removal, manufacturers
and practitioners have been obligated to seek safer and
more effective results.
Although the technology is relatively new, it has
already generated much interest among clinicians and
patients alike because of its ability to delay hair
regrowth, and non-invasively remove large areas of
J Lepselter
and M Elman
Msq P.O. Box 3021, Caesarea 38900,
Dermatology and Lasers Clinic,
21 Leonardo Devinci Street
Tel-Aviv, 64733 Israel
INTRODUCTION: In the past cen-
tury, unwanted hair has been
traditionally treated with multi-
tudes of techniques that were
found to be slow, tedious, painful,
impractical, and resulted in poor
long-term efficacy. Consequently,
there has been a public demand
for a novel, rapid, reliable, safe,
and affordable hair removal tech-
nique. In the last decade, laser and
light-based technology for hair
removal became one of the fastest
growing procedures in modern
cosmetic dermatology.
OBJECTIVE: To discuss the latest
scientific and clinical issues in the
field of photoepilation as evolved
in the past decade: hair biology,
laser physics and skin optics, tech-
nology and clinical experience.
RESULTS: From substantial clinical
experience, it becomes apparent
that in the ideal subject with fair
skin and dark hair, a single treat-
ment can reduce hair by 10–40%;
three treatments by 30–70%; and
repeated treatments by as much as
90%. These results persist for as
long as 12 months. Diffuse and
perifollicular cutaneous erythema
and pigmentary changes are the
most common adverse side effects.
Most complications are generally
CONCLUSIONS: Photoepilation,
when properly used, offers
clear advantages when compared
with older, traditional techniques.
Although an ever-increasing num-
ber of published studies have con-
firmed the safety and short and
long-term efficacy of photoepila-
tion, the technology still has limits
and risks. (J Dermatol Treat (2004) 15:
Received 7th July 2003
Accepted 14th November 2003
Keywords: Anagen Bulb Follicular erythema Hair follicle Laser
Joseph Lepselter, PhD, Msq PO Box 3021, Caesarea 38900, Israel. Tel
z972 4 627 5357; Fax z972 4 627 5368; E-mail:
Journal of Dermatological Treatment (2004) 15, 72–83
#2004 Journal of Dermatological Treatment. All rights reserved. ISSN 0954-6634
DOI: 10.1080/09546630310023152
hair with minimal discomfort, and a low incidence of
However, efficacy and safety of hair
removal by laser and light-based technology varies
considerably among manufacturers due to differences in
patients’ skin–hair biology traits, optimization of electro-
optical parameters and clinical protocols.
The purpose of this review is to discuss the major
scientific and clinical issues in the field of photoepilation
that have evolved in the last decade. Pertaining to our
discussion will be the following topics: hair biology;
biomedical optics and laser physics; clinical experience
with selected technologies; and essential issues in
Hair biology
A hair follicle consists of three regions: the infundibu-
lum, isthmus, and hair bulb. The general anatomy of
hair follicle is shown in Figure 1. The inferior segment of
the hair follicle lies below the arrector pili muscle
insertion and includes the hair bulb and dermal papilla.
As will be discussed later, this area is of great impor-
tance in photoepilation. On average, the bulb is appro-
ximately 4 mm in depth from the surface of the skin, a
considerable depth of penetration required by the laser
light-based systems.
The hair bulb is made up of germi-
native matrix cells along with interspersed melanocytes.
The dermal papilla, located in the base of the bulb, is fed
by the bloodstream, which carries nourishment to produce
new hair. The bulge is located approximately one-third of
the distance down from the skin surface to the follicle bulb.
Dermal sheath cells and epidermal outer root cells are
found in the follicle bulb. These cell types extend into the
isthmus and infundibulum of the hair follicle and play an
important role in hair growth.
Human hair grows in a cyclic pattern. The cycle
consists of a growth or anagen phase followed by
intermediate degradation of a portion of the follicle,
known as the catagen phase and then by a resting
period when no growth occurs the telogen phase.
Figure 2 describes the three phases of the hair growth
cycle. It appears that different areas of the body, in
addition to having shorter anagen cycles, have varying
percentages of hairs actually in the anagen phase.
The anagen duration varies greatly depending on age,
season, gender (anagen in thigh hair in men is 54 days
versus 22 days in women), body site, hormones and
underling genetic susceptibilities.
The catagen phase is
generally 3 weeks in duration whereas the telogen
phase usually lasts approximately 3 months. At any
given time, the majority of the hair follicles (80–85%)
are in the anagen phase and the remaining follicles are
either in the catagen phase (2%) or the telogen phase
Table I shows the duration and percen-
tage of the hair cycle in relation to body areas.
For effective hair removal a laser/light source should
damage one or more growth centers of hair, and the
pluripotential cells of the bulge, dermal papilla, and hair
matrix must be treated in the anagen cycle. It is during
the anagen phase that melanin production occurs and
becomes part of the growing follicle. It is also in the
anagen phase that damage can affect the structure
theoretically responsible for hair generation. During the
telogen phase, the dermal papilla moves upward toward
the bulge region and stimulates the onset of the anagen
phase. In this active growth phase, the papilla moves
down away from the bulge mass and the hair matrix
cells regress during the catagen phase. Thus, depending
on the stage of the hair cycle, the distance between the
bulge region and the dermal papilla varies along with
the depth of the dermal papilla within the dermis. These
structures represent targets for hair follicle damage, and
relative movement with respect to the skin structure
attenuate their photothermal susceptibility to a fixed
wavelength laser beam. Thus, to achieve long-term hair
removal, it is essential to destroy the structures that are
responsible for hair growth: the bulge and bulb.
Laser physics and skin optics in
hair removal
Laser hair removal is a multifactorial process that involves
complex photothermal reaction via the epidermis–dermis
Figure 1
Hair follicle anatomy in photoepilation.
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
matrix, aimed to cause hair follicle damage while sparing
the epidermis. Thus, hair follicle eradication bya laser light
source is a function of various laser (e.g. power, spot size,
irradiation time and repetition rate) and tissue (absorption
and scattering coefficients, density, heat capacity and
thermal conductivity) parameters.
The laser source may be continuous mode or pulsed.
A continuous mode laser emits a continuous stream of
light as long as the medium is excited, resulting in
heating and vaporization of the target tissue. Alterna-
tively, a pulsed laser will emit light only in short
amounts, which may vary from nanoseconds to as long
as seconds. Various sources of laser/light-based technol-
ogy exist, including continuous light, flashlamp, radio
frequency, high-voltage discharge, diodes and others.
When the lasing medium is excited, the molecules are
stimulated to a higher energy level. These excited
molecules tend to decay spontaneously to their original
lower energy level realizing a photon. All emitted
photons bear a constant phase relationship with each
other in both time and phase coherency. In turn, all
laser light photons travel in the same direction with low
divergence collimated. Finally, laser light has high
irradiance, since all the light is concentrated into a
narrow spatial band resulting in a high radiant power
per unit area.
Energy refers to the number of photons delivered and
is measured in joules ( J). Power is measured in watts
(W) and refers to the delivery rate of energy (1 W=1 J/s).
Fluence is the total energy delivered per unit area and is
measured in J/cm
. Pulse duration is the amount of time
laser energy is applied (ns, ms). The pulse frequency is
measured in hertz (1 Hz=1 pulse/s). Wavelength is
measured in nanometers (nm) and refers to the distance
between the peaks of the light waves and is used to
characterize the type of light (green, red, yellow).
The technology employed for hair removal by lasers/
light-based systems is based on the principle of selective
Figure 2
Hair follicle cycle. (A) Anagen phase: hair matrix cells migrate outward from the shaft and the melanin load is at its highest. (B) Catagen
phase: the follicle detaches from the papillae and contracts eventually falling out. (C) Telogen phase: mitosis ceases, the hair matrix
regresses and the papilla retracts to a place near the bulge (apoptosis).
Body area Anagen hair (%) Telogen duration Density (cm
) Follicle depth
Scalp 85 4 months 350 3–5 mm
Beard 70 10 weeks 500 2–4mm
Moustache 65 6 weeks 500 1–2 mm
Armpits 30 3 months 65 3–4mm
Bikini line 30 3 months 70 3–4 mm
Legs 20 4 months 60 2–3 mm
Table I
Duration and percentage of hair in the anagen and telogen phase (ref. 9)
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
photothermolysis. According to this principle, selective
thermal destruction of a target will occur if sufficient
energy is delivered at a wavelength well absorbed by the
target within a time period less than or equal to the
thermal relaxation time (TRT) of the target.
is the time it takes for the target to cool (half of its
baseline temperature) and transfer the heat to sur-
rounding structures. Under these conditions, it is
possible to selectively target structures (e.g. hair follicle)
while sparing the surrounding structures or tissues. The
target site for the selective destruction of hair follicles
can either be endogenous melanin or exogenous
A corollary of selective photothermolysis is thermo-
kinetic selectivity. This theory proposes that for the
same chromophore, a longer pulse duration allows
intrapulse cooling of smaller targets more rapidly than
larger targets. Longer pulse durations are predicted to
limit thermal damage to the epidermis. If the pulse
duration exceeds the thermal relaxation time of the
basal cell layer (about 0.1 ms) or entire epidermis (about
10 ms), these structures will cool as they are heated
during the laser pulse. In other words, larger targets
(hair follicles) can be selectively injured more than
smaller targets of the same chromophore (epidermis).
Recently, a novel concept of laser hair removal uses
the thermal damage time (TDT) rather than the
traditional hair follicle TRT concept that has been
described. Studies indicate that the ideal pulse duration
for medium to coarse hair reduction may be longer than
the TRT of the hair follicle. Since the melanin occupies a
much smaller volume compared with the follicle, heat is
conducted from the shaft and melanized portion of the
bulb to surrounding structures according to the laws of
thermal diffusion. It has been suggested that widening
the pulse duration allows an increase in the threshold of
epidermal damage. As we have learned more about the
mechanism of hair removal, it has become evident that
the true targets for permanent hair removal are located
at a distance from the hair shaft, at the outer root
sheath of the follicle (stem cells), and the base of the
follicle. This important observation has required recon-
sideration as to the appropriate laser parameters,
particularly pulse width and energy density.
When considering photothermal destruction of hair
follicles, there are three parameters that need to be
considered: wavelength, pulse duration, and fluence.
The longer the wavelength, the deeper the laser light
penetrates the skin. To damage hair follicles, laser light
must be absorbed by a chromophore within the follicle.
Most lasers target the endogenous chromophore mela-
nin within the pigmented hair shaft by delivering red or
near-infrared wavelengths. Melanin is the primary light
absorber in the optical window between 600 nm and
1100 nm. Wavelengths in this range are poorly absorbed
by competing chromophores such as hemoglobin and
water and penetrate deeply into the dermis.
It should
be remembered though that the absorption of light by
melanin decreases with longer wavelengths and that
oxyhemoglobin and melanin have similar absorption at
wavelengths at 750–850 nm.
The ability of these wavelengths to damage hair
correlates directly with the amount and type of melanin
within the follicle: pheomelanin and eumelanin. Dark
hair that contains large amounts of eumelanin readily
absorbs these wavelengths and is most susceptible to
laser-induced damage.
In theory, the use of longer
wavelengths increases the ratio of energy deposited in
the dermis to the epidermis, which results in relative
bulb heating and epidermis sparing. However, although
there is more melanin absorption at a wavelength of
755 nm than 800 nm, larger energy density (fluence)
must be employed during 800 nm than with a 755 nm
wavelength laser. In the case of brown and black hairs,
where the target chromophore is eumelanin, long-
pulsed diode lasers at a wavelength of 800 nm were
found to be safe and clinically effective.
The necessary energy density (i.e. fluence) for the
coagulation of hair follicle is proportional to the hair
shaft diameter, as long as the bulb and follicle thickness
are proportionate to hair shaft diameter; the thinner the
hair, the smaller the energy density level.
In general,
the fluence of the laser should be greater than or equal
to the threshold fluence for tissue destruction. To
confine thermal damage to the hair follicle, the laser
pulse duration should lie between the TRT for epidermis,
which is approximately 3–10 ms, and the TRT for the
hair follicles which is approximately 40–100 ms. Using
this concept to deliver light of the right combination of
wavelength, energy fluence, and pulse duration, it is
possible to precisely target the hair follicle and improve
long-term hair removal.
The laser pulse width plays an important role in
determining selective photothermolysis. High energy,
short pulses of laser light cause extremely rapid heating
of the target, with a rapid expansion of the thermal
plasma. If the pulse width is too long, however, there
will be insufficient time for the heat to dissipate, and
undesirable temperature increase will occur with ther-
mal injury to non-follicular structures, which could
result in scarring or irregularities in pigmentation.
Ideally, the spot size should be as large as possible
to reduce scattering of the light. When light is applied
to the skin using a small spot size, the scattering of
photons diffuses the beam rapidly. The fluence decays
very quickly as a function of depth, so that most of the
energy is dissipated in radial directions (outwards) and
cannot reach the hair bulbs. With a large spot size,
light penetration is more efficient since the ‘source’ of
photons has an almost planar geometry. In human skin,
about 15–20% of incident light at 700 nm penetrates to
a depth of 3 mm. Thus, by using a larger spot size
scattering of light in the dermis is lessened, leading to a
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
greater depth of penetration and a lower threshold
Clinical experience
Since the first laser-assisted hair removal device was
cleared in 1995, more than 15 laser systems have been
approved by the Food and Drug Administration (FDA) to
specifically target hair follicles.
These systems include
ruby (694 nm), alexandrite (755 nm), diode (800–
1000 nm), Q-switched and long-pulsed neodymium:
yttrium-aluminum-garnet (Nd:YAG; 1064 nm) and
intense pulsed light (IPL) sources (550–1200 nm).
Devices that target exogenous chromophores are carbon
particles plus Q-switched Nd:YAG laser (1064 nm) and
5-aminolevulonic acid. A summary of different com-
mercially available hair removal devices is presented
in Table II.
Normal-mode ruby laser (694 nm)
The pulsed ruby laser was the original system used to
perform melanin-based selective photothermolysis of
hair. The ruby laser delivers red light at a wavelength
of 694 nm. Three ruby lasers have been approved by
the FDA for hair removal: EpiLaser/E2000 (Palomar);
EpiPulse (Sharplan/ESC); and RubyStar (Aesculap
Mediteo). Because of the high melanin absorption at
694 nm, ruby lasers are most useful for light-skinned
(Fitzpatrick skin types I–III) individuals with dark hair.
In a recent study, Allison et al studied the long-term
hair regrowth in three patient groups: top lip (n=25),
axillae (n=25) and legs (n=9). Two treatments were
given on the right and left sides at monthly intervals. A
third treatment was given randomly to one side. Hair
counts of the experimental sites were made at monthly
intervals for 1 year. Long-term hair reduction was
achieved in all patients. A single treatment reduced hair
counts by up to 75%. Three treatments had an impact
for 2 additional months, but not long term. Unexpected
spontaneous hair reduction was found 5 months
following treatment and lasted 2 months. This ruby
laser produced a persistent two-thirds reduction in hair
count over 8 months of follow-up and no significant
regrowth follow-up to 12 months.
Studies with short-
term follow-up have observed 37–72% reduction at 3
months after one to three treatments, to a 38–49% hair
reduction 1 year after three treatment sessions.
In a long follow-up study, Grossman et al studied 13
patients with fair skin and dark hair. Patients were
treated once on the thighs or back at fluences of
20–60 J/cm
and pulses of 270 msec. In all subjects, hair
regrowth was delayed for 1–3 months at all fluences.
A complete regrowth was present in five out of 13
patients. At 1–2 years follow-up, four of the seven
patients had persistent hair loss, which was greatest in
the sites treated with the highest fluence.
Chana and Grobbelaar
prospectively assessed the
long-term results of ruby laser depilation in 346 con-
secutive patients who underwent hair removal at 402
anatomical sites. The patients were treated using a
ruby laser, with the mean power ranging from 8.6 J to
15.7 J according to skin type. Results were assessed
using two outcome measures: the percentage reduction
in hair density and the hair-free interval. The median
reduction in hair density was 55% (range 0–100%) at a
median time of 1 year after the last treatment session.
The median hair-free interval was 8 weeks. Patients
underwent a median number of four treatment sessions.
Forty-three of the 346 patients were treated at more
than one anatomical site. Of the sites treated, a 75%
reduction in hair density was achieved in 22%, 90%
reduction was achieved in 2.2%, and complete depila-
tion was achieved in only 0.7%. Darker colored hair
was more effectively treated. Treatment efficacy was not
affected by anatomical site, with the exception of the
faces of male patients, which were found to be par-
ticularly resistant to treatment. There was a significant
correlation between the number of treatments given and
the outcome. The overall complication rate was 9.0%
(36 of 402 sites) with respect to pigmentary changes
and blistering, but varied according to Fitzpatrick skin
type. The complication rate was highest in skin types V
Pulse duration
Spot size
Repetition rate
(Hz) Cooling mean
Mythos-500 (Msq) 810 0–400 5–120 10612 up to 4 Sapphire contact
Q-switched Nd:YAG (Thermolase) 1064 10
2–3 7 10 Not needed
Long-pulsed ruby (Palomar) 694 3 10–40 10 1 Sapphire contact
Long-pulsed alexandrite (Cynosure) 755 5, 10, 20, 40 5–50 10–15 up to 2 Cold air flow
LightSheer (Star/Coherent) 810 5–100 10–60 12612 up to 2 Sapphire contact
Long-pulsed Nd:YAG (Laserscope) 1064 1–50 up to 150 1–4 up to 4 Contact cooling
Super-long-pulse 1000 (Palomar) 810 200–1000 up to 100 10 up to 3 Contact cooling
Laser/light source 550–1200 15–100 up to 45 10645 0.5 Circulating cooling
Table II
Parameters of selected hair removal lasers and light sources
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
and VI (24.7%), with no complications in skin type I.
Although a greater than 50% reduction in hair density
was achieved in half of the 346 patients treated,
complete depilation was achieved in only an extremely
limited number of patients. In other controlled studies,
the ruby laser (one to four sessions) proved to be more
efficacious for hair reduction than shaving or waxing
Alexandrite laser (755 nm)
The alexandrite laser allows greater depth of penetration,
making it relatively safe in darker-skinned (Fitzpatrick
skin types I–IV) individuals. However, melanin absorp-
tion is somewhat less at the wavelength of alexandrite
(755 nm) when compared with the ruby (694 nm).
Alexandrite lasers for hair removal were cleared by
the FDA to market in the USA in 1997. EpiTouch Alex
(ESC Sharplan Medical Systems), GentleLASE (Candela
Laser Corp.), and Photogenica LPIR (Cynosure, Inc.) are
currently available.
The reported success rate of hair removal using the
alexandrite has ranged from 40% to 80% at 6 months
after several treatments. In a controlled randomized
study, McDaniel et al showed a 40% to 56% reduction
of hair growth at 6 months after one treatment with a
variable-pulsed alexandrite laser on the lip, leg, and
This study found that one treatment with a
variable-pulsed alexandrite laser produced maximum
hair regrowth reduction at 6 months of 40–56% for the
lip, leg and back. Sites treated with a 10 ms pulse
duration were found to have a significantly better hair
reduction rate that those treated with 5 ms or 20 ms
pulse widths.
Laughlin and Dudley found an average of 43%
reduction at 6 months plus ‘one growth cycle’ after a
single treatment at the bikini line, with 60% of sites
having greater than 30%.
An uncontrolled study,
using a uniform protocol, demonstrated a mean of 74%
hair reduction 1 year after five treatment sessions at the
bikini line. The average patient had a 78% clearance of
hair noted at 1 year with no evidence of scarring or
pigmentary changes.
In 150 dark-skinned patients (skin types IV–VI)
treated with the alexandrite laser (18 J/cm
, 40 ms),
side effects occurred in about 2% of cases.
studies have shown that the 20 ms pulse duration
reduces the risk of epidermal damage and pigmentary
alteration, but treatment is more painful when longer
pulse durations are used.
Diode laser (800–1000 nm)
Diode lasers for hair removal were cleared by the FDA to
market in the USA in 1997. Because of the longer
wavelength, the active cooling, and the longer pulse
widths, individuals with darker skin can be treated more
safely with this system. In general, the diode laser
system has been found to be better tolerated by patients
with darker skin types (V–VI) than the ruby laser.
Overall, clinical studies with the diode laser system
have reported variable success rates ranging from 65%
to 75% hair reduction at 3 months after one to two
treatments with fluences of 10–40 J/cm
,tow75% hair
reduction in 91% of individuals 8 months after three to
four treatments at 40 J/cm
In a recent study, Fiskerstrand and colleagues
compared two systems (side-by-side study) with different
pulse structures. The radiant exposure was selected to a
value of 35 J/cm
, which is frequently used in the clinic
in accordance with the manufacturer’s recommenda-
tions. Twenty-nine patients with hair color ranging
from light brown to black on the upper lip were studied.
Three treatments were performed at 6–8 week intervals.
The percentage hair reduction and acute and long-term
side effects were evaluated after treatment. The average
hair reductions 6 months after the first treatment were
similar in both diode systems (49% and 48% clearance).
No scarring or pigmentary change of the skin was
observed after any of the treatments with either laser.
However, differences in acute side effects such as degree
of erythema and burned hairs were observed. No stati-
stically significant differences in hair removal efficacy
were observed.
Rogachefsky et al
have evaluated the clinical effi-
cacy and side effect profile of a modified 810 nm diode
laser device operating in a super-long-pulse mode (200–
1000 ms). Ten female subjects with Fitzpatrick skin
types I–VI received either one or two laser treatments at
eight test sites. Super-long-pulse durations of 200–
1000 ms were evaluated with delivered fluences ranging
from 23 to 115 J/cm
. Subjects were followed for 6
months after the first treatment. The clinical results
show that safe hair removal in all skin types can be
accomplished with an 810 nm diode laser delivering
super-long-pulse durations. Pain and complications
were greatest at the highest pulse duration (1000 ms)
and the highest fluence (115 J/cm
). Optimal hair
reduction at 6 months (31%) was achieved at a thermal
diffusion time of 400 ms (46 J/cm
Dierickx et al evaluated the effectiveness and safety in
ninety-five subjects with dark hair (Fitzpatrick skin types
I–IV). Subjects were treated at baseline and 1, 3, 6, 9,
and 12 months after treatment. One versus two treat-
ments were compared. Treatment results demonstrated
both hair growth delay (in all patients) for 1–3 months
and permanent hair reduction of 46% (40 J/cm
pulse width).
Several other studies have demonstrated the efficacy
of the diode laser hair removal. In one study of
50 patients, quantitative hair counts performed for 9
months after treatment showed long-lasting and pos-
sibly permanent hair loss.
Lou et al who looked at
light-skinned patients with a single session, detected a
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
significant regrowth rate ranging from 65% to 75% 20
months after treatment. Two-session treatments were
associated with a longer growth delay, ranging from
47% to 66%.
Sadick et al studied 24 female subjects
(skin types II–IV) were treated three times at monthly
intervals with a new 810 nm diode laser (spot size
12 mm, pulse width 50 ms, fluence 25–35 J/cm
). A
mean hair removal efficiency of 74% and 79% was
noted at 3 and 6 months, respectively.
Nd:YAG laser (1064 nm)
The Q-switched 1064 nm Nd:YAG laser with or without
topical carbon suspension was one of the first laser
systems used to remove hair. The poor absorption by
melanin at this wavelength coupled with an epidermal
cooling device makes the long-pulsed Nd:YAG laser a
safe treatment option for patients with the darkest skin
phototypes (III–VI) and, therefore, for darker Fitzpatrick
skin types the long-pulsed Nd:YAG is preferred to the
ruby laser. However, because of reduced absorption by
follicular melanin, very high fluences (50–100 J/cm
are required to damage pigmented hair follicles.
Theoretical considerations to improve the performance
of the Nd:YAG laser have been proposed, including an
improvement in the exogenous chromophores used.
In addition, the Nd:YAG laser may be useful in the
treatment of light hairs, when used with the topically
applied carbon suspension. Most of the Nd:YAG systems
are Q-switched, with pulses ranging from 10 ns to
30 ms, although Nd:YAG equipment delivering non-Q-
switched long pulses is also available. Several long-
pulsed Nd:YAG lasers have been approved by the FDA
for hair removal or laser treatment of darker skin types.
Overall, clinical studies have demonstrated less hair
reduction with the Nd:YAG laser compared with those
results published with the ruby or alexandrite lasers. In a
recent study, Rogachefsky et al
evaluated the efficacy
of a long-pulsed Nd:YAG laser system. Twenty-two
subjects were treated with a cryogen spray-cooled long-
pulsed Nd:YAG laser. Four adjacent sites were assigned
to each subject, and were treated with parameters of
50 J/cm
with a 25 ms pulse duration; 60 J/cm
with a
50 ms pulse duration; 80 J/cm
with a 50 ms pulse dura-
tion; and control. Hair counts were obtained immediately,
and 1 week, 1 month, and 3 months after treatment, and
multivariate regression analysis was used to determine
the significance of hair reduction. At 3 months, the
higher settings of 60 J/cm
and 50 ms and 80 J/cm
50 ms were statistically significant for reduced mean
hair counts (p=0.014, p=0.042, respectively), while the
lowest setting at 50 J/cm
and 25 ms was not significant
In a prospective clinical study with 29 volunteers,
Lorenz et al
investigated the efficacy, side effects,
and the long-term results of a long-pulsed Nd:YAG for
hair removal in different hair colors and skin types.
Treatment was performed on the lower leg with a long-
pulsed Nd:YAG. Five test areas were treated one to five
times at monthly intervals; one served as a control.
Follow-up investigations were performed at each ses-
sion, and 3, 6, and 12 months after the last therapy.
The investigators reported after 1 month a hair loss of
greater than 50% in 44.9% of the areas treated once.
With up to five treatments, this percentage increased to
71.5%. One year after therapy, a greater than 50% hair
reduction was still present in 40% of the five-treatment
areas and in 0% of the areas treated only once.
Early published medical papers using Nd:YAG with
carbon lotion reported a 27% to 66% reduction at 3
months after one treatment.
In a different study with
long-pulsed Nd:YAG, Goldberg and Samady found that
in 15 subjects (Fitzpatrick skin types I–III) hair reduc-
tion varied between 50% and 60% at 3 months. Laser
energy was delivered through a 1 mm spot size, 30 ms
pulse duration and fluences of 125–130 J/cm
for facial
hair and 150 J/cm
for non-facial hair. No complica-
tions or adverse effects were reported at any of the
follow-up examinations.
Intense pulsed light (550–1200 nm)
This system delivers broad spectrum, non-coherent
radiation with wavelengths of 550–1200 nm. One of
four filters (590 nm, 615 nm, 645 nm or 695 nm) is
used to eliminate shorter wavelengths. In general, filters
with higher cut-off values are used with darker skin
types. Cooling means are recommended (i.e. gel) when
higher energy (30–65 J/cm
) light pulses are used.
These properties allow for great variability in selecting
individual treatment parameters and adapting to dif-
ferent skin types and indications. However, because of
the wide spectrum of potential combinations of wave-
lengths, pulse durations, pulse frequency, and fluences,
a great deal of experience is required when using IPL
technology. Proper patient selection and critical diag-
nostics serve to keep the adverse effects of the treatment
to a minimum.
Treatment with IPL may be useful for light colored
hair, although more treatment sessions are generally
required. Several studies have demonstrated the long-
term efficacy of the device. In a study of 67 subjects of
Fitzpatrick skin types I–IV, mean hair loss was 48% at 6
months or more after a single treatment. There were no
statistically significant differences in hair count after
single versus multiple treatments.
In one study, 60%
hair reduction was reported 12 weeks after a single
treatment with various cut-off filters (34–44 J/cm
, two
to five pulses, 1.5–3.5 ms, 20–50 ms delays). Adverse
effects included post-treatment erythema in 7%, hyper-
pigmentation in 3%, and blistering in 11%.
In a non-
controlled study of 14 subjects treated with IPL, and
followed for more than 12 months after the last
treatment, a mean of 83% hair reduction was obtained
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
after two to six treatments.
The authors attributed the
high success rate obtained to the ability of the tech-
nology to provide energy of long wavelengths, selected
high-energy fluences on a specific range and long pulse
durations. However, the results from this study should
be interpreted with caution due to the absence of
controls and lack of uniform treatment and follow-up
control. Side effects and complications of IPL treatment
are similar to those seen after laser-assisted hair removal,
and include rare instances of blistering, crusting, and
transient dyspigmentation.
In summary, the ruby laser (694 nm), alexandrite
laser (755 nm), diode laser (800 nm), intense pulsed
light source (550–1200 nm) and the Nd:YAG laser
(1064 nm), with or without the application of carbon
suspension, work on the principle of selective photo-
thermolysis with the melanin in the hair follicles as the
chromophobe. Regardless of the type of laser used
multiple treatments are necessary to achieve satisfactory
results. After repeated treatments hair clearance of
30–50% is generally reported 6 months after the last
treatment. Patients with dark skin (Fitzpatrick skin
types IV and V) can be treated effectively with com-
parable morbidity to those with lighter skin. Although
there is no obvious advantage of one laser system over
another in terms of treatment outcome (except the
Nd:YAG laser, which is found to be less efficacious, but
more suited to patients with darker skin), laser para-
meters may be important when choosing the ideal laser
for a patient.
Essential issues in laser hair
Hair removal is an ambiguous term that may carry
different meaning for the patient, the physician and the
industry. ‘Permanent hair removal’ should be distin-
guished from ‘permanent hair reduction’. The former is
defined as the long-term, stable reduction in the number
of hairs regrowing after a treatment regime, which may
include several sessions. The number of hairs regrowing
must be stable over time greater than the duration of
the complete growth cycle of hair follicles, which varies
from 4 to 12 months according to body location.
Permanent hair reduction, on the other hand, does not
necessarily imply the elimination of all hairs in the
treatment area. This means that although laser treat-
ments with these devices will permanently reduce the
total number of hairs, they will not result in a per-
manent removal of all hair. Complete hair loss refers to
a lack of regrowing hairs (i.e. the number of regrowing
hairs is reduced to zero). Complete hair loss may be
either temporary or permanent. Laser treatment usually
produces complete but temporary hair loss for 1–3
months, followed by partial but permanent hair loss.
Temporary growth delay seems to be caused by laser
damage induction of the telogen phase. Permanent hair
loss seems to be associated with miniaturization of hair
Optimal follicle damage
Which hair cycle phase is the most appropriate, and
which follicular elements cause hair-shaft regeneration
is a subject of debate. In mice, Lin and colleagues noted
that during the anagen phase there was heterogeneous,
but widespread injury to the epithelium, increasing with
increasing fluence (1.47–3.26 J/cm
). However, no
follicular damage was observed during the catagen or
telogen phases at any of the fluences used. Full hair
regrowth occurred 28–56 days after laser exposure
administered during the catagen or telogen phases for
all fluence levels. In contrast, regrowth after laser
exposure in the anagen phase was fluence-dependent:
hair regrowth was moderate (1.47 J/cm
) and none
(3.16 J/cm
In humans it appears that the most essential variable
is the presence of the pigmented hair shaft within the
skin that functions as a chromophore. It is therefore
likely that both anagen and telogen follicles are sensitive
to laser treatment. Because the telogen bulb is high in
the dermis one might argue that this would be the
optimal time for treatment; however, the superficial
location is undermined by the bulb being poorly
melanized. In early anagen the bulb is well melanized
and still fairly superficial; this may present the best time
for treatment. If the damage is not permanent during
this cycle, follicles move into the telogen stage as they
fall out. Because the duration of the hair cycle differs
for different body sites (Table I), repeat treatments are
usually done when there is a wave of rapid hair
regrowth or between 4 and 8 weeks.
Another issue is whether the hair follicle is able to
regenerate from the bulge area if the papilla is destroyed
by a photothermal source. Some researchers claim that
hair follicles can regenerate in the absence of the hair
while others maintain that the destruction of
the hair papilla is essential for permanent epilation.
The recent bulge-activation hypothesis maintains that
the bulge area of the outer root sheath near the arrector
pili muscle insertion contains pluripotential cells, which
contribute to the new hair matrix when induced by the
dermal papillae during the late telogen phase.
injury to the stem cells in the bulge area would lead to
follicular destruction.
Safety and skin color
Although numerous lasers are available for laser-
assisted hair removal, their use in individuals with a
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
dark skin type presents many challenges due to com-
petition from epidermal melanin. The ideal candidate for
hair removal is a light-skinned individual with dark
terminal hair. Dark skinned patients with high epider-
mal melanin content are prone to adverse side effects
ranging from immediate pain and pigmentary distur-
bances to scarring. Despite the selection of appropriate
wavelengths and pulse widths of the targeted chromo-
phore, there is light absorption by the overlying epider-
mal melanin (Fitzpatrick skin types IV–VI).
Short wavelength (694, 755 nm) hair removal lasers
can be quite successful in lighter skin types. However,
laser hair removal in Asians can be difficult, and mul-
tiple treatments are usually required for effective treat-
ment. Recently, Hussain et al
evaluated the safety and
efficacy of alexandrite laser hair removal in 144 Asian
subjects with Fitzpatrick skin types III–V. The authors
reported that no individuals had scarring or long-term
pigmentary changes and concluded that there does not
appear to be an exact correlation in Asian skin between
complications occurring after test patch treatment and
those seen with subsequent treatments.
In a multicenter prospective study, laser hair removal
was associated with a low incidence of side effects that
were self-limiting in the majority of cases. The highest
incidence of side effects was seen in patients with darker
skin treated with the long-pulsed ruby laser.
the parameters for laser hair removal emphasize use for
Caucasians (Fitzpatrick skin types I, II, or III). The
characteristics of oriental skin and hair are black, coarse
hairs in darker skin (Fitzpatrick skin types IV or V) and
therefore the hair is more difficult to remove by laser.
Recently, Lu et al
report 146 oriental patients (156
body sites) who underwent treatment with the long-
pulsed alexandrite laser (755 nm wavelength) depila-
tion system. Minimal and transient complications were
In a retrospect study of 900 patients who underwent
laser-assisted hair removal, Nanni and Alster
direct association of skin type on the risk of side effects.
Table III describes selected adverse side effects that may
occur during or following laser/light-based hair removal
treatment. Adrian and Shay
studied laser hair removal
in African-American patients with skin types V and VI.
Histologic studies examined efficacy and side effects in
an effort to optimize laser hair removal procedures in
this patient population. It was found that both laser
modes could be used safely in skin type V and VI
African-American patients; however, longer pulse dura-
tions enabled the delivery of higher fluences with minor
and acceptable postoperative complication profiles.
In order to avoid thermal damage of the epidermal
matrix, current laser and non-laser devices use various
parameters of cooling means by different techniques.
Currently popular cooling techniques include contact
(circulating cold water at 2–6C or sapphire), cryogen
cooling or forced flow of chilled air. In general, the
rational of cooling the skin is to allow the delivery of
higher fluences and short pulse widths into the hair
During long pulse modes (w100 ms), how-
ever, the epidermis tolerates a narrower temperature
gradient in respect of the cooling method applied. Thus,
to achieve effective epidermal protection, the hair color
(i.e. black, blond), skin type (Fitzpatrick skin types I–VI)
and cooling types should be carefully considered. Since
adverse side effects are directly correlated with skin type,
with darker-skinned and tanned patients experiencing a
much higher rate of complications, skin types IV–VI and
tanned skin are best treated with a diode laser (800 nm)
or a Nd:YAG (1064 nm) laser. A physician who has a
good understanding of hair biology, laser optics, and
patient skin phenotypes is able to improve patient
outcome and reduce untoward adverse side effects.
Nevertheless, no system can provide fully predictable
Treatment frequency
Factors that affect the outcome of treatment include the
hair growth cycle, skin color, hair color and density,
and the quality of the individual hairs. Table IV shows
factors that may influence photoepilation outcome.
Because the duration of the hair cycle differs for dif-
ferent body sites, repeat treatments are usually done. As
a general rule, 6 to 10 laser sessions are required during
the first year to achieve long-term epilation. With most
laser systems, a single treatment can reduce hair by
10–40%; three treatments by 30–70%; and repeated
treatments as much as 90%. These results are main-
tained at post-treatment follow-up for as long as 12
months. Wendy and Geronemus reported a lower level
of hair regrowth after three laser treatments on the face
compared with the back, shoulders and arms.
on the duration of cycle length, hairs on the head have
a relatively short telogen phase (6–12 weeks). Thus, a
1-month interval between treatments is a sufficient time
elapse for progression to the anagen phase. On the
trunk, a 2-month interval is more appropriate. Figures 3
Event Occurrence
Dyspigmentation (hyper or hypo) Common
Itching, stinging (during treatment) Common
Pain Atypical
Follicular erythema Common
Epidermal erythema Common
Purpura Uncommon
Crusting/scab formation Uncommon
Swelling Uncommon
Erosions Uncommon
Herpes simplex Uncommon
Scarring Rare
Table III
Adverse side effects during/following photoepilation
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
and 4 depict the before (A) and after (B) clinical results
of laser hair removal.
Controversies and limitations
With the proliferation of devices targeting hair and
unsubstantiated claims by manufacturers, significant
confusion exists in this field. Although an ever-
increasing number of published studies have confirmed
the long-term efficacy of laser and light-based treat-
ments, the technology still has limits and risks. Most
studies on laser hair removal are uncontrolled and
have included fewer than 50 patients; none have been
blinded, and all have used a variety of treatment pro-
tocols, equipment, skin types and hair colors. In
addition, none of the presently utilized lasers have
been proven to destroy hair permanently and long-term
results are still lacking. Because lasers and light-based
systems were rushed onto the market without a full
understanding of their capabilities and limitations, it is
vital that researchers, practitioners and consumers
continue to make their experience known to the pub-
lic. Current data on laser and light-based hair removal
are limited by the short duration for which this
technology has been practiced. More long-term studies
with state-of-the-art laser hair removal technology are
still needed to elucidate the optimal parameters clini-
cally appropriate for safe and effective results in all skin
and hair types/colors.
Laser parameters
Spot size
Pulse width
Skin cooling system
Skin phenotype
Fitzpatrick skin type I–III
Fitzpatrick skin type IV–VI
Hair characteristics
Hair thickness
Hair color
Follicle depth
Anagen/telogen follicles ratio
Hair anatomical location
Cushing syndrome
Polycystic ovarian disease
Hormonal medications
Testosterone and estradiol
Growth factors (IGF-1)
Photosensitive medications
Plucking, waxing
Sun tanning
IGF=insulin-like growth factor
Table IV
Factors influencing hair removal efficiency
Figure 4
Clinical results. Skin type III: male. (A) Before
and (B) 3 months after three treatments plus
control. (Courtesy of Pio Donnarumma, MD,
Napoly, Italy.)
Figure 3
Clinical results. Skin type III: female. (A) Before and
(B) 3 months after three treatments. (Courtesy of
Pio Donnarumma, MD, Napoly, Italy.)
J Lepselter and M Elman Biological and clinical aspects in laser hair removal
The use of lasers/light-based technology in the treatment
of unwanted hair has become commonplace in our
society. Today, less than a decade after the first laser hair
removal debut, there are at least 20 manufacturers
producing more than 40 laser/light-based systems.
The acceptance of photoepilation by both physicians and
patients is a direct reflection of the high degree of efficacy,
low side effects and few complications. The benefits of this
technology, however, have largely been limited to
individuals with dark hair and relatively fair skin.
The major challenge in the field of photoepilation
continues to be the development of technology that not
only permanently and significantly reduces the number
of hairs but also provides permanent and complete hair
removal for all skin and hair types and colors. With
current technology, the average clearance rate is 20–75%
after 1–6 months of follow-up. Long-term studies with a
follow-up of more than 1 year are needed to find out
whether permanent hair removal can be accomplished.
Recently, the increasing public demand for a low-cost
hair removal service has urged new manufacturers to
develop low-priced, compact sized systems, which still
need clinical validation and long-term follow-up.
Photoepilation, although better studied than most
methods and more strictly regulated, has yet to be
proved permanent in all patients and in all hair colors.
With the rapid pace of technological advancements and
continued studies of hair biology, laser physics, skin optics
and cooling means, it is anticipated that permanent hair
removal will be achieved in the near future.
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J Lepselter and M Elman Biological and clinical aspects in laser hair removal
... It is applied to treat a wide range of skin conditions, including Rosacea, a chronic skin condition of the face or eyes in women, and hair removal. [4,5] A new concept for the use of lasers to treat skin malignancies induced by excessive exposure to ultraviolet radiation during infancy and adolescence has been developed. [6,7] Laser treatment has a shortened healing time, a smaller incision size, and no chemical side effects such as hair loss, nausea or vomiting, fatigue, irritation of the mucous membranes or mouth, and diarrhea when compared to conventional treatments such as surgery and chemotherapy. ...
... Numerous lasers of different wavelengths are available for LHR, however, an increase in various side-effects and complications have been reported when treating Fitzpatrick skin types IV-VI. This is due to the presence of a higher concentration of melanin in the epidermis which functions as a competing absorber of laser light [18]. These side effects and complications can be minimized when the treatment is performed by a professional laser and skin care therapist [4]. ...
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Background: Lasers of different wavelengths have been developed for use in permanent hair reduction. An increase in the manufacturing of home-use laser hair removal devices allows for these treatments to be performed in the comfort of your own home at an affordable cost. Objective: To evaluate the effectiveness of permanent hair reduction using a Diode laser in comparison to the Silk'n™ Flash and Go Lux (475-1200 nm) home-use laser. Methods: Fifteen females received six axillae laser hair removal treatments at two to four-week intervals using either a professional laser or home-use laser device. Photographs and hair counts were taken before each treatment and at a three week follow up. A T-test was used to evaluate statistical significance, and regression analysis to determine a difference in the effects. Pain scores and side effects were recorded by a visual analogue scale in a satisfaction questionnaire. Results: The professional laser showed an overall hair reduction of 85% on the right axilla and 88% on the left axilla. The home-use laser showed an overall reduction of 52% on the right axilla and 46,3% on the left axilla. Mild side effects were experienced for both laser devices. There were no serious adverse effects reported, safety features are effective to a certain extent. Conclusion: The Flash & Go Lux home-use laser can effectively reduce hair at a slower rate than the Diode laser. The home-use laser device offers protection against accidental exposure to light and use on darker skin types. Risks of retinal damage due to long-term exposure to home-use laser light are still cause for concern.
... Below the arrector pili muscle is the inferior portion of the hair follicle and contains the hair bulb and dermal papilla. The hair bulb is made up of germinative matrix cells along with interspersed melanocytes [77]. ...
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The present study analyzes degrees of hair damage, hair diameter, cell length, morphological, and structural changes in human hair of the male radiation workers at Al-Tuwaitha Nuclear Site compared with the control group by using scanning electron microscopy (SEM). Also,the effect of concentration of trace element have been studied by using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP:OES), and investigated the activity of uranium, cesium, and strontium in scalp hair sample of male radiation workers who worked in Al-Tuwaitha Nuclear Site and control group by using alpha spectroscopy, gamma spectroscopy, liquid scintillation counter. In addition to use, the micronuclei analysis, nuclear division index as biomarkers for detection of the effects of ionizing radiation exposure in radiation workers chronically exposed to low dose ionizing radiation in Al-Tuwaitha Nuclear Site compared to control group. This study includes 25 male scalp hair samples (non dying, and non - smoker) and 50 male blood samples from radiation worker, aged (25- 61 year), as well as 25 male scalp hair samples also non dying, non-smokers, and 50 male blood samples blood from control group, aged (25-58 year). A statistically significant difference (p-value: 0.00161) has been found between the radiation worker and control group with respect to the scanning electron microscope (SEM) scores with the extent of damage in morphological and structural hair sample being more in the radiation workers as compared to the control groups. To validate the analytical of levels of Cs, Sr, and U concentration in scalp hair of radiation workers and control groups, U levels of radiation workers has been significantly higher compared to control group (p-value: 0.0026), whereas Cs (p-value: 0.0978), and Sr (p-value: 0.1920) has been non-significant difference between radiation workers as compared to the control group when analyzed by ICP:OES. To investigate the isotope 238U, 137Cs, 90Sr in scalp hair, there has been an analysis by alpha spectroscopy, gamma spectroscopy, and liquid scintillation counter respectively. The result reveals no statistically significant difference seen of 238U (p-value: 0.611527496), 137Cs (p-value: 0.456310275), 90Sr (< MDA) respectively between hair sample of radiation worker and control group. Blood samples have been taken for micronuclei (MN) and nuclear division index (NDI). MN number in peripheral blood lymphocytes has been measured by using cytokinesis-block micronuclei (CBMN) assay according to standard protocols. The frequency of MN (mean±SD) per 1000 binucleated cells has been significantly higher (p < 0.05) in the radiation workers (0.01912± 0.00539 MN/ cell), compared to the control group (0.0106± 0.0028 MN/cell). The micronucleus frequency has been found to increase systematically with donor age. NDI has calculated mono-nucleated, bi�nucleated, tri-nucleated and tetra-nucleated lymphocyte cell per 1000 lymphocytes scored according to criteria proposed by Fenech method. The result showsthat the mean of NDI values of lymphocytes obtained from radiation worker group has been 1.23 ± 0.007 when compared with the mean of NDI values in control 1.356 ± 0.0153, (p-value: 5.238E-11). In addition to that, our study has measured Hb (the means of Hemoglobin concentration) (p-value: 0.293), PCV ( percentage pocket cell volume) (p-value: 0.665), total WBC ( total white blood cell count) (p-value: 0.388), and total RBC ( total red blood cell count), (p-value: 0.967), MCV (mean cell volume) (p-value: 0.815), MCH (mean cellular hemoglobin concentration) (p-value: 0.542), MCHC (mean cellular hemoglobin concentration) (p-value: 0.219), and RDW (percentage of red cell distribution width) (p-value: 0.307) by using the scanning microscope and the automatic complete blood analyzer. The present result shows no significant differences p<0.05 in the shapes and sizes of red blood cells for the group of workers compared to the control group. In conclusion, the human hair might be useful to investigate the concentration of elements and activity of isotopes in environmental work, bioanalytical studies, clinical and medical diagnosis, occupational health, and forensic science, and nuclear plant. The obtained results occupationally exposed to low levels of ionizing radiation may be associated with increased deposits on the hair shaft surface. Besides, the data obtained in the analysis of concentration indicates that inductively coupled plasma optical emission spectroscopy (ICP:OES) provides good precision and accuracy of the results. Also revealed concentration of uranium has been higher in radiation workers than in control group, while non-significant difference was found for cesium, strontium concentration, this is due to cesium, strontium only artificial form but uranium presents in natural and artificial form. In addition to hair from radiation worker and control groups. It has been founded equally exposed with the same level of 238U, 137Cs and 90Sr within normal limit under Minimal Detection Activity (MDA). While, in biological assay it shows a high frequency of micronuclei of radiation worker compared to control group. The current results of micronuclei frequency (MN) and nuclear division index (NDI) have been within normal values according to the technical report of International Atomic Energy Agency (IAEA), September 2011.
... These results corroborate findings from the Yuan et al. study, whereby electrolysis was associated with significantly longer sessions, greater expenses, and more pain compared to LHR [7]. This divergence is due, in part, to the ability of LHR to be applied to large areas of hairbearing skin at once [19]. Despite this advantage, LHR may be less optimal for patients of darker skin tones, due to risks of superficial burns and discoloration secondary to the destruction of the melanin [20]. ...
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Background Preoperative genital hair removal (PGHR) prior to penile inversion vaginoplasty (PIV) is vital to prevent postoperative hair-induced stenosis of the neovaginal canal, yet the approach remains unstandardized. We sought to better characterize current methods of PGHR and their effect on outcomes. Methods Adult transgender females who underwent PIV at a single center from December 2018 to July 2022 were invited to participate in an online survey via email. Reminder emails were distributed once every 2 weeks for a total of four reminders. Data concerning PGHR method, postoperative hair growth, and satisfaction were collected. Results Of the 128 patients contacted, 28 (21.9%) completed the survey. Twenty-three patients (82.1%) endorsed PGHR prior to PIV. Laser hair removal (n = 11, 47.8%) was the most common method, followed by electrolysis (n = 7, 30.4%), and at-home kits (n = 5, 17.9%). Treatment sessions most frequently began > 6 months preoperatively (n = 9, 39.1%), occurring once weekly (n = 12, 52.2%) for a total of 5–6 treatments (n = 7, 30.4%). Postoperatively, 9 patients (32.1%) developed hair growth. There were no differences in incidence, time to hair growth, satisfaction with sexual function, or overall satisfaction between PGHR methods. PGHR was associated with lower rates of hair growth (0.069, CI 0.006–0.769), while hair growth was associated with lower satisfaction with sexual function (0.100, CI 0.024–0.427), and lower overall satisfaction (0.069, (0.006–0.769)). Conclusions While the ideal method of PGHR remains unclear, preventing hair growth is important to preserve sexual function and maximize postoperative satisfaction. Patients should be properly counseled regarding alternative hairless methods of vaginoplasty, including the intestinal approach, to optimize outcomes. Level IV, Risk/Prognostic study
... Ignoring the possible shadow effect provided by hair on skin zones where hair density is high, like the scalp, in general and in "naked skin", radiation in the UV range is not expected to reach more than 160 µm below the skin surface (into the dermis) [275,276]. Since hair bulbs from terminal hairs are located between 1 and 5 mm below the surface, in the subcutaneous fat, active follicular melanocytes are more protected from UV direct stimulation than epidermal melanocytes [277]. ...
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Simple Summary The frequency of use of permanent hair dyes to change natural colour are associated with fibre damage and with an increased risk of serious health problems. The future of hair dyeing could be the topical modulation of the pigment production that occurs in special cells, called melanocytes, localized in the hair roots. The success of such approaches is dependent on expanding and deepening our knowledge on hair pigmentation biology. In this context, the paper aims to critically review the vast bibliography on mammalian pigmentation having in view the topical modulation of hair follicle biology to produce a desired change in the hair fibre colour. Abstract The natural colour of hair shafts is formed at the bulb of hair follicles, and it is coupled to the hair growth cycle. Three critical processes must happen for efficient pigmentation: (1) melanosome biogenesis in neural crest-derived melanocytes, (2) the biochemical synthesis of melanins (melanogenesis) inside melanosomes, and (3) the transfer of melanin granules to surrounding pre-cortical keratinocytes for their incorporation into nascent hair fibres. All these steps are under complex genetic control. The array of natural hair colour shades are ascribed to polymorphisms in several pigmentary genes. A myriad of factors acting via autocrine, paracrine, and endocrine mechanisms also contributes for hair colour diversity. Given the enormous social and cosmetic importance attributed to hair colour, hair dyeing is today a common practice. Nonetheless, the adverse effects of the long-term usage of such cosmetic procedures demand the development of new methods for colour change. In this context, case reports of hair lightening, darkening and repigmentation as a side-effect of the therapeutic usage of many drugs substantiate the possibility to tune hair colour by interfering with the biology of follicular pigmentary units. By scrutinizing mammalian pigmentation, this review pinpoints key targetable processes for the development of innovative cosmetics that can safely change the hair colour from the inside out.
... 8 Factors such as skin type and hair color, as well as different levels of hair thickness and depth, affect the appropriate laser selection. [9][10][11] Recently, devices presenting a combination of wavelengths have shown to produce high effective hair reduction with no related risks. 12 Novel diode laser systems combining three wavelengths (755, 810, 1064 nm) in a single pulse have been developed to target different structures of the hair follicle for the removal of unwanted hair and to provide long-term hair reduction suitable for diverse hair varieties and all skin types. ...
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Background: Laser has been long accepted as a solution for excess or unwanted hair growth yet traditional lasers are not always ideal for safe and effective outcome for all skin types and hair characteristics. A diode laser module combining three wavelengths (755, 810, and 1064 nm) in a single pulse was developed to provide a fast and long-term solution for subjects with various profiles. Aims: To evaluate the safety and efficacy of a Triple wavelength diode laser module for hair removal treatment in all skin types (Fitzpatrick I-VI). Subjects and methods: This was a prospective, dual centered, single-arm study. Subjects were treated with a novel diode laser module. Thirty-six subjects were enrolled, sixteen with Fitzpatrick skin types I-IV (46%) and twenty with Fitzpatrick skin types V-VI (54%). Treatment areas were axilla and bikini lines. Subjects underwent 4 treatment sessions at 6 weeks ± 5 days intervals and attended a follow-up visit 3 months after the last treatment session. 2D digital photographs were taken at baseline and at the follow-up visit, and a hair count was conducted by three blinded evaluators. Results: A significant reduction in hair count between baseline and the 3-month follow-up visit was observed in both axilla and bikini lines for all skin types. The mean hair reduction was 41.5 ± 19.4% and 48.1 ± 20.9% in the axilla and bikini line, respectively. A significant hair reduction was also observed within skin type groups; mean hair reduction 45.5 ± 16.9% and 40.3 ± 17.2% in skin types I-IV and V-VI, respectively, indicating similar efficacy for both light and dark skin types. No serious adverse events were reported. Conclusions: This study demonstrates that the Soprano Titanium laser platform is safe and effective for hair removal treatment in all skin types.
... Wskazuje się na fakt, że pacjenci o ciemnej karnacji (typ skóry od IV do VI) oraz osoby opalone są bardziej narażone na powikłania po depilacji, szczególnie pod kątem oparzeń. Stąd przy takich typach skóry zaleca się stosowanie lasera diodowego (800 nm) lub lasera Nd: YAG (1064 nm) w celu minimalizacji powikłań [23]. Niektóre źródła podają informację, że zwiększone prawdopodobieństwo powikłań pojawia się już przy III typie skóry i może objawiać się ...
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Laser hair removal requires knowledge of their physical basis and the biophysical phenomena they induce in the skin. Lasers differ in such categories as wavelenght, Energy density and laser beam size. These elements are important while selecting the right device for the skin type and individual characteristics of the patient. Knowledge of the physiology of hair and the photothermolysis that occurs during epilation, allows the treatment to be carried out correctly and safely, and the entire proces of hair elimination to be controlled. Previous studies indicate a numer of factors that determine the effectiveness of the procedure, including the parameters of the device or skin type. Despite the high degree of safety and effectiveness of the laser epilation procedure, it is also pointed out that there are undesirable consequences that may appear in response to the effects of laser light.
Laser and light therapies have offered significant advances in dermatological therapy in the past several decades, having evolved significantly from the early use of the ruby laser in 1960 to the current time when such technologies have become a mainstay of treatment for a host of medical and surgical conditions. The chapter covers laser‐, light‐ and energy‐based devices and their applications for aesthetic purposes. Given the large number of devices available, it is essential for the laser surgeon to understand their capabilities and limitations. In order to provide patients with optimal treatments, the laser surgeon needs to accurately identify the target structure, select an appropriate laser‐ or light‐based system, and then tailor the specific parameters for the intended target.
Background: Laser hair removal is an increasingly prevalent trend of cosmetic procedures. The purpose of this study was to assess the effectiveness of hair reduction among several types of laser interventions. Methods: The selected studies searched in PubMed and EMBASE were assessed for quality of evidence, and extracted data on absolute hair count and hair reduction rate. Qualitative data were synthesized using standardized mean difference (SMD) in frequentist network meta-analysis because various measurement units were used among selected studies. Inconsistency and small study effects were examined by design-by-treatment interaction model and comparison-adjusted funnel plot. Results: A total of 13 randomized controlled trials (RCTs) (n = 652) were contributed to network meta-analysis. Pooled results revealed that diode laser showed significantly lower absolute hair count within three-month (SMD = -13.21, 95% confidence interval [CI]: -22.25 to -4.17) and around six months follow-up (SMD = -11.01, 95% CI: -18.24 to -3.77) as compared with those in control group, but no significant difference among laser interventions. All side effects observed were transient without leaving any permanent scars. Conclusion: Eliminating unwanted hair with lasers or intense pulsed light is safe and effective; however, which type of intervention is more beneficial in the long-term process should be studied with a longer follow-up time.
Laser hair removal is one of the fastest growing procedures in cosmetic dermatology. Since the first PDA-approved laser-assisted hair removal system was introduced in 1995, the number of such systems has increased exponentially. Originally the procedure was appropriate only for fair-skinned patients, but new wavelength and pulse-width variations and improved cooling mechanisms have made it safe for a large range of skin types. Increased energy outputs have improved efficacy. However, the technology still has limits and dangers, which the lay press has highlighted in high-profile articles and television features. In this article, I provide an algorithm for optimizing clinical results and patient satisfaction with hair removal.
Conference Paper
Despite the widespread use of lasers for hair removal there is little data published on the incidence of side effects from this treatment. We aimed to generate data on a large number of patients receiving laser hair removal to obtain an accurate assessment of the incidence and type of side effects resulting from treatment. A multicentre prospective study of patients attending for laser hair removal was conducted to determine incidence of side effects in relation to skin type and laser(s) used. Laser hair removal is associated with a low incidence of side effects which are self-limiting in the majority of cases. Highest incidence of side effects was seen in darker skinned patients treated with the long pulsed ruby laser. Laser hair removal is inherently safe. For darker Fitzpatrick skin types the long pulsed Nd:YAG laser is preferred to the ruby laser.
Laser-assisted hair removal is the most efficient method of long-term hair removal currently available. Several hair removal systems have been shown to be effective in this setting: ruby laser (694nm), alexandrite laser (755nm), diode laser (800nm), intense pulsed light source (590 to 1200nm) and the neodymium:yttrium-aluminium-garnet (Nd:YAG) laser (1064nm), with or without the application of carbon suspension. The parameters used with each laser system vary considerably. All these lasers work on the principle of selective photothermolysis, with the melanin in the hair follicles as the chromophobe. Regardless of the type of laser used multiple treatments are necessary to achieve satisfactory results. Hair clearance, after repeated treatments, of 30 to 50% is generally reported 6 months after the last treatment. Patients with dark colored skin (Fitzpatrick IV and V) can be treated effectively with comparable morbidity to those with lighter colored skin. Although there is no obvious advantage of one laser system over another in terms of treatment outcome (except the Nd:YAG laser, which is found to be less efficacious, but more suited to patients with darker colored skin), laser parameters may be important when choosing the ideal laser for a patient. Adverse effects reported after laser-assisted hair removal include erythema and perifollicular edema, which are common, and crusting and vesiculation of treatment site, hypopigmentation and hyperpigmentation (depending on skin color and other factors). Most complications are generally temporary. The occurrence of hypopigmentation after laser irradiation is thought to be related to the suppression of melanogenesis in the epidermis (which is reversible), rather than the destruction of melanocytes. Methods to reduce the incidence of adverse effects include lightening of the skin and sun avoidance prior to laser treatment, cooling of the skin during treatment, and sun avoidance and protection after treatment. Proper patient selection and tailoring of the fluence used to the patient’s skin type remain the most important factors in efficacious and well tolerated laser treatment. While it is generally believed that hair follicles are more responsive to treatment while they are in the growing (anagen) phase, conflicting results have also been reported. There is also no consensus on the most favorable treatment sites.
Hirsutism affects 5‐10% of unselected women, depending on ethnicity and definition. The past two decades have seen the development of lasers for the removal of unwanted hair, using selective destruction of the hair follicle without damage to adjacent tissues. Selective photothermolysis relies on the absorption of a brief radiation pulse by specific pigmented targets, which generates and confines the heat to that selected target. In general, laser hair removal is most successful in patients with lighter skin colours and dark coloured hairs. Some studies have documented the results of laser hair removal in a controlled setting, although few have extended their observations beyond 1 year. In general, treatment with the ruby, alexandrite or diode lasers, or the use of intense pulsed light results in similar success rates, although these are somewhat lower for the neodymium:Yttrium‐Aluminum‐Garnet (nd:YAG) laser. Overall, laser hair removal should not be considered ‘permanent’, at least when considering the current data available. Repeated therapies are necessary, although complete alopoecia is rarely achieved and it is unclear at what point the maximum benefit is achieved from multiple therapies. While larger prospective, controlled, blinded and uniform studies are still needed, laser hair removal appears to be a useful adjuvant in the treatment of the hirsute patient.
Objective: To determine the most effective treatment parameters for laser-assisted hair removal using a Q-switched neodymium:yttrium-aluminum-garnet (Nd: YAG) laser. Design: Prospective study to determine the effectiveness of Q-switched Nd:YAG laser—assisted hair removal under varying pretreatment protocols. Hair growth was assessed after laser treatment, and the results were compared with those of wax epilation at 4, 12, and 24 weeks. Setting: A private ambulatory laser facility and academic referral center. Intervention: Laser-assisted hair removal was performed under 4 different pretreatment conditions. Eighteen areas of unwanted body and facial hair from 12 study subjects were divided into 4 quadrants. Wax epilation followed by application of a carbon-based solution and exposure to Q-switched Nd:YAG laser radiation was performed on 1 quadrant. A second quadrant was wax epilated and exposed to Q-switched Nd:YAG laser radiation without prior carbon solution application. A third quadrant was exposed to laser radiation alone, and a final quadrant was wax epilated to serve as the control. Follow-up evaluations at 1, 3, and 6 months consisted of photographic documentation, manual hair counts, and patient hair-density estimates. Main Outcome Measure: Percentage of hair regrowth as assessed by objective hair counts and patient subjective evaluations. Results: Mean percentage of hair regrowth at 1 month was 39.9% for the wax-carbon-laser quadrant, 46.7% for the wax-laser quadrant, 66.1% for the laser-alone quadrant, and 77.9% for the wax control quadrant. The percentage of hair regrowth approximately doubled by 3 months but was significantly delayed in all laser-treated quadrants regardless of pretreatment protocol. Full hair regrowth in all anatomic locations was observed by month 6. Patient subjective evaluations of hair density closely approximated hair count data. No adverse effects or long-term complications were observed. Conclusions: A single hair-removal treatment with the Q-switched Nd:YAG laser is safe and effective in delaying hair growth for up to 3 months. Although the combination of pretreatment wax epilation and topical carbon solution application was effective, laser irradiation alone, with or without wax epilation, also provided a significant delay in hair growth.Arch Dermatol. 1997;133:1546-1549
This essay is a critique of a revolutionary hypothesis, and of the language used to frame it, that offers a novel interpretation for the dynamics of the follicular cycle by distinguishing, distinctly, germinative cells in the bulge from matrical cells in the bulb. Curiously, this intriguing "bulge-activation hypothesis" elicited practically no response in the scientific literature, and our critique is designed to rectify that.
Despite the widespread use of lasers for hair removal there are few data published on the incidence of side effects from this treatment.Objective The aim of this study was to generate data on a large number of patients receiving laser hair removal to obtain an accurate assessment of the incidence and type of side effects resulting from treatment.MethodsA multicenter prospective study of patients presenting for laser hair removal was conducted to determine incidence of side effects in relation to skin type and laser or lasers used.ResultsLaser hair removal is associated with a low incidence of side effects that are self-limiting in the majority of cases. The highest incidence of side effects was seen in patients with darker skin treated with the long-pulsed ruby laser.Conclusions Laser hair removal is inherently safe. For darker Fitzpatrick skin types the long-pulsed neodymium:yttrium-aluminum-garnet laser is preferred to the ruby laser.