Shaving effects on percutaneous penetration: Clinical implications

Abstract

Context:
Human/animal shaving biology.

Objective:
To assess the effect of shaving on percutaneous penetration and skin function.

Methods:
We screened 500+publications in Pub Med, Scopus, Cochrane Library and pertinent journals out of which only 17 were deemed relevant. Terms for searches included shaving and skin, percutaneous penetration and shaving, skin absorption and shaving, absorption of dyes and shaving, skin penetration, effects of shaving and absorption, shave and dyes, axillary shaving and stratum corneum, shaving and breast cancer, shaving and infections, etc.

Result:
Shaving appears to have an exaggerated effect on percutaneous absorption; however, some studies do not support this evidence.

Conclusion:
Shaving enhances percutaneous penetration of some chemicals; however this effect is species and chemical specific. Further investigations of chemicals of varying physio-chemical properties are mandated before a generalized theory can be promulgated.

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Cutaneous and Ocular Toxicology
ISSN: 1556-9527 (Print) 1556-9535 (Online) Journal homepage: http://www.tandfonline.com/loi/icot20
Shaving effects on percutaneous penetration:
clinical implications
Muhammad Hamza, Hassaan Tohid & Howard Maibach
To cite this article: Muhammad Hamza, Hassaan Tohid & Howard Maibach (2015) Shaving
effects on percutaneous penetration: clinical implications, Cutaneous and Ocular Toxicology,
34:4, 335-343, DOI: 10.3109/15569527.2014.966109
To link to this article: http://dx.doi.org/10.3109/15569527.2014.966109
Published online: 03 Nov 2014.
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ISSN: 1556-9527 (print), 1556-9535 (electronic)
Cutan Ocul Toxicol, 2015; 34(4): 335–343
!2014 Informa Healthcare USA, Inc. DOI: 10.3109/15569527.2014.966109
REVIEW ARTICLE
Shaving effects on percutaneous penetration: clinical implications
Muhammad Hamza
1
, Hassaan Tohid
2
, and Howard Maibach
1
1
Department of Dermatology, University of California San Francisco, San Francisco, USA and
2
Sindh Medical College, Dow University of
Health Sciences, Karachi, Pakistan
Abstract
Context: Human/animal shaving biology.
Objective: To assess the effect of shaving on percutaneous penetration and skin function.
Methods: We screened 500+publications in Pub Med, Scopus, Cochrane Library and pertinent
journals out of which only 17 were deemed relevant. Terms for searches included shaving and
skin, percutaneous penetration and shaving, skin absorption and shaving, absorption of dyes
and shaving, skin penetration, effects of shaving and absorption, shave and dyes, axillary
shaving and stratum corneum, shaving and breast cancer, shaving and infections, etc.
Result: Shaving appears to have an exaggerated effect on percutaneous absorption; however,
some studies do not support this evidence.
Conclusion: Shaving enhances percutaneous penetration of some chemicals; however this effect
is species and chemical specific. Further investigations of chemicals of varying physio-chemical
properties are mandated before a generalized theory can be promulgated.
Keywords
Blade and absorption, dyes and skin
permeation, hair removal, razor and shave,
shave and absorption, stratum corneum
and axillary shaving
History
Received 24 July 2014
Revised 1 September 2014
Accepted 12 September 2014
Published online 30 October 2014
Introduction
Shaving is an art involving robust hair removal
1,2
. Men usually
shave their beards, mustache, chest, head, axilla and pubic area
while women shave axilla, pubic area, arms, legs and
occasionally the chest. Shaving has become a trademark of
beauty in women and a sign of attraction in men, which is the
reason it is attributed as a cosmetic modification. However,
shaving is also performed on religious, cultural, hygienic as
well as personal grounds.
Stratum corneum is a main rate-limiting barrier to
percutaneous penetration
3
and a main layer damaged by
shaving
3,4
. Shaving is often accompanied by visible and/or
sensory irritation
3
. This irritation may be due to cuts and
nicks which can impair the natural barrier to the irritants
5,6
.
Percutaneous penetration and its effects on shaving is a
topic which has not been studied in depth. We conducted this
overview to ascertain the relation between percutaneous
penetration and shaving, and effect of shaving on stratum
corneum.
Methods
We screened 500+research articles in databases, e.g. Pub
MED, Scopus, Google Scholar, Cochrane library and pertin-
ent journals of which 17 were deemed relevant.
Search terms included but not limited to hair removal,
adverse effects of shaving, after-shave and penetration/
absorption, blade and penetration, razor and shave, razor and
absorption, razor and minor injuries, dermatitis and shaving,
allergy and shaving, skin damage and shaving, stratum corneum
and shaving, shaving and skin, percutaneous penetration and
shaving, skin absorption and shaving, absorption of dyes and
shaving, skin penetration, effects of shaving and absorption,
shave and dyes, axillary shaving and stratum corneum, shaving
and breast cancer, shaving and infections, etc.
Data from relevant articles was studied, compared and
organized to draw a conclusion regarding the effects of
shaving on percutaneous penetration.
Results and discussion
The biological effects of shaving are incompletely studied.
Female axillary shaving has not been studied in depth,
although it is a common practice worldwide. Physical effects
on the stratum corneum and physiological effects on the
epidermis and dermis are encountered due to shaving. For
example, 20% of the material removed in male facial shaving
comprises skin (and remaining hair)
1
. Two processes could
influence barrier properties following shaving
(i) Increased epidermal hyper proliferation that occurs after
chronic shaving
7,8
and
(ii) Direct physical damage to the stratum corneum by
scratching/friction which also has been shown at the
raised perifollicular areas
8
.
Marti et al.
4
utilized image analysis of the stratum
corneum surface both pre- and post-shaving which revealed
Address for correspondence: Dr. Howard Maibach, University of
California, School of Medicine, 90 Medical Center Way, San
Francisco, CA 94143-0989, USA. Tel: 707-999-1268. Fax: 415-673-
9693. E-mail: maibachH@derm.ucsf.edu

distinct opaque lines because of uplifting skin flakes with a
corresponding significant increase (statistically) in the scali-
ness parameter from 0.48 to 0.61 demonstrating immediate
damage to cornified layer. These have been interpreted as
uplifted skin flakes, likely to promote ingress of potentially
irritating ingredients.
Direct damage to the stratum corneum was supported by
the observation that dry shaving perturbed barrier function in
the upper layers of stratum corneum as shown with a lower
Colorimetric Index of Mildness (CIM) value. Physical
damage to the stratum corneum was reflected in a significant
increase in dry skin.
Marti et al. studied axillary shaving involving two groups.
The first shaved one axilla daily (1/day) while group 2
comprised of shaving the other axilla once weekly (1/7 days).
By visual assessment, irritation was significantly elevated in
the first group. However, determination of the barrier function
by CSM and analysis of stratum corneum lipid composition
indicated only a limited effect of increased shaving on stratum
corneum parameters.
They assessed the role of shaving on antiperspirant use. An
extension of the antiperspirant patch test was employed. Pre-
shaving of the volar forearm followed by the standard 47 h
patch test revealed that compared to unshaved skin, the
antiperspirant irritancy increased significantly (biologically)
(Figure 1).
Although damage to the stratum corneum was detected,
major effect of shaving appeared to be on skin irritancy.
Hence, they investigated the effect of shaving on a pro-
inflammatory stimulus using histamine iontophoresis in
conjunction with dry shaving. An area of the forearm was
lightly dry shaved five times with a disposable razor.
Histamine iontophoresis was performed immediately after
shaving. There were two control sites adjacent to the shaved
sites. Itch perception increased significantly at the shaved
sites as compared to the control sites (Figure 2).
They concluded that damage to the surface barrier
properties allows increased entry of irritant molecules and
gentle shaving is capable of having profound effects on
inflammatory response of the epidermis and the structure of
the stratum corneum.
Lucova et al.
9
studied the damage to the skin barrier due to
shaving in relation to permeation of chemicals and also
assessed dermal absorption values of two dyes, namely,
Brilliant Blue and Patent Blue through skin as compared to
intact skin. They used pig skin from the back of the pig’s ears,
which contains no adipose tissue. They showed the shaving
process manifested in a noticeable permeation of both dyes
from three dosing model products (after-shave, facial cleanser
and O/W emulsion) into deeper compartments of the diffusion
system as demonstrated in Tables 1 and 2.
Lucova et al. observed that vehicles influence permeation of
absorption of dyes and the greatest amount of both dyes
penetrated into the epidermis from ethanol-based aftershave.
Their findings were consistent with the renowned skin-
penetration-enhancing effect of ethanol-water solvent
system
7,8,10
.
The study suggested shaving caused only a slight decrease
in thickness of full-thickness pig-ear skin (FTS) approx. 1%,
but significant increase in transdermal electrical conductivity
(TEC) values (3.5- to 5.7-fold) compared to intact FTS and
shaven skin showed permeation higher than intact FTS.
Lucova et al. concluded the normal process of shaving
markedly enhances the potential for systemic availability of
both dyes from hydrophilic vehicles. This finding was of
concern with respect to the frequency of skin treatment after
shaving with cosmetic products containing dyes that people
use for long periods.
Turner et al.
6
and others assessed the impact of shaving
on underarm skin in which the thickness of the axillary vault
and fossa were measured using Optical Coherence
Tomography (OCT) and the response of the axilla to
histamine iontophoresis was also investigated. Additionally
they investigated the impact of an antiperspirant roll-on
formulation on irritation and self-perceived sensory properties
of the axilla.
The study involved 16 subjects; measurements were taken
from the shaved and unshaved areas and showed an increased
Figure 1. The irritation potential range of antiperspirant aerosol bases under patch 47 h, both in pre-shaved and unshaven control skin. Adapted from
Marti
4
.
336 M. Hamza et al. Cutan Ocul Toxicol, 2015; 34(4): 335–343

epidermal thickness of shaved areas, which could be due to
chronic hyper proliferation and local thickening to facilitate
repair of the barrier and protection from subsequent shaving
events. They further performed histamine iontophoresis in the
vault and fossa of both axilla of the nine volunteers who were
asked to shave both axilla 2d prior to the study. One axilla
was shaved immediately prior to iontophoresis. Histamine
iontophoresis in both vault and axilla resulted in an increase
in both wheal and flare in the shaved axilla as compared to the
unshaved control.
This supported the previous studies which show that the
shaving of axillary skin can damage the epidermal barrier
4
while shaved skin has demonstrated to respond to increased
itch and erythema following iontophoretic delivery of hista-
mine
3
. They also performed a randomized control study of
30 female volunteers. In the test phase, subjects were given
two-coded antiperspirant roll-on formulations labeled for
right and left underarm. Test phase consisted of 2/week
underarm shaving and exaggerated product use and irritation
assessed by an expert assessor 3/week. In the provocation
phase, daily underarm shaving along with exaggerated
application (4 times daily) of a control antiperspirant roll-on
was performed. Results showed a decrease in irritation due to
the roll-on used in the test phase compared to the control roll-
on formulation used in the provocation phase.
Turner et al. concluded that axillary shaving results in
removal of skin and increased potential for irritation and itch.
Moreover, axillary vault showed a greater thickening in the
epidermis than the unshaved area of the fossa. The response to
histamine iontophoresis in the shaved axilla was greater than
that of the unshaved which supported the fact that shaving
causes damage to epidermal barrier.
Banerjee and Ritschel
11
studied transdermal permeation of
vasopressin using female Sprague–Dawley rats. Effect of
shaving was studied by shaving rat skin one day before the
study with an electric shaver after preliminary clipping of hair
before excision. Skin was allowed to heal for 24 h. This was
compared to Flynn’s study
12
of stripping the skin 25 times
Figure 2. The effect of shaving on histamine-induced itch. Histamine iontophoresis was performed on untreated control site (control 1), followed by
pre-shaved site (shave) and then by untreated control site (control 2). Perceived itch was determined using a VAS scale. Adapted from Marti
4
.
Table 2. The amounts of test compounds detected in a given compartment (epidermis) of the in vitro diffusion system after
24-h exposure of ex vivo full-thickness pig-ear skin (FTS) to Patent Blue V and demonstration of increased penetration
post-shaving.
Membrane
Compartment of
diffusion system
After-shave
ethanol-based PB
Facial cleanser
ethanol-free PB O/W emulsion PB W/O emulsion PB
Intact FTS Epidermis 82 ± 4 79 ± 13 44± 13 40 ± 8
Shaven FTS Epidermis 105 ± 30 99 ± 32 48± 14 40 ± 5
Adapted from Lucova
9
.
Table 1. The amounts of test compounds detected in a given compartment (epidermis) of the in vitro diffusion system after
24-h exposure of ex vivo full-thickness pig-ear skin (FTS) to Brilliant Blue FCF. Membrane.
Compartment of
diffusion system
After-shave
ethanol-based BB
Facial cleanser
ethanol-free BB O/W emulsion BB W/O emulsion BB
Intact FTS Epidermis 65 ± 8 56 ± 13 14 ± 3 13 ± 2
Shaven FTS Epidermis 89 ± 17 110 ± 12 18 ± 3 23 ± 6
Note the penetration increases with shaving. Adapted from Lucova
9
.
DOI: 10.3109/15569527.2014.966109 Shaving effects on percutaneous penetration 337

with cellophane tape to remove the stratum corneum.
Vasopressin solution was used to study the effect of shaving
on its permeation.
Flux was increased 5-fold due to shaving and the lag time
of vasopressin was reduced significantly in comparison to
light clipping. Stripping (25 times) resulted in the removal of
stratum corneum and showed a marked increase in vasopres-
sin permeation.
This shows skin is partially damaged and demonstrates the
stratum corneum is one of the main barriers to permeation of
vasopressin. The results are consistent with that of Bruger and
Flexner
13
, which demonstrated an increase in insulin perme-
ation due to shaving.
Guo et al.
14
examined Cyclosporin A using Kunming mice
(kept under normal laboratory conditions). The hair of test
mice was trimmed short with a pair of scissors. To destroy the
integrity of stratum corneum, the other group of mice was
shaved with scrapper. Application area on the abdominal skin
was 2 2 cm. Flexible and conventional vesicles were
administered respectively and left to dry out.
Results of the in vivo study demonstrated that with
the application of flexible vesicles on unshaven skin,
serum drug concentration of 53.4 ± 9 ng/ml was detected
after 2 h of permeation and amounted to 154 ± 27 ng/ml 6 h
later. Whereas, after the stratum corneum of mouse skin was
destroyed post-shaving, a large amount of drug into blood was
Figure 3. The Cyclosporin A serum concentration in murine blood as a function of time after an epicutaneous administration of flexible vehicles under
normal skin and shaved skin. Serum concentration increases significantly after epicutaneous application of f lexible vesicles post-shaving compared to
normal skin. Adapted from Guo
14
.
Figure 4. No difference between shaved and unshaved ventral forearm skin in vivo in the percutaneous absorption of testosterone in rhesus monkey
utilizing the urinary excretion method. Adapted from Wester
15
.
338 M. Hamza et al. Cutan Ocul Toxicol, 2015; 34(4): 335–343

Table 3. The contents of the various studies mentioned in the text.
S. # Study Study design No. of subjects Method Results Comments
1 Marti et al.
4
/
Effect of shaving on
axillary Stratum
corneum.
Case-control
study.
30 Humans 1. 2 groups studied for 4 weeks.
Group 1: shaved axilla once a week.
Group 2: shaved axilla once a day
7days/week)
All participants used a roll-on antiper-
spirant 4 times daily.
2. Antiperspirant patch test:
Pre-shaving of the volar forearm fol-
lowed by the standard 47- hr patch test
was compared to unshaven skin.
3. Histamine iontophoresis was performed
after shaving an area of the forearm
five times. In addition, the two adja-
cent sites were tested as control sites:
Control 1: prior to shaving.
Control 2: after iontophoresis at the
shaved site.
1. Dry shaving immediately perturbed
barrier function in the upper layers of
the stratum corneum as observed with
a lowered CIM value.
2. The antiperspirant irritancy increased
significantly.
3. Itch perception and histamine-induced
neurogenic flare significantly
increased at the shaved site.
Chemicals used: antiperspirant
roll-on.
2 Lucova et al.
9
/Absorption
of triphenyl-methane
dyes Brilliant Blue and
Patent Blue through
intact skin, shaven skin
and lingual mucosa from
daily life
6-month old pigs Ears and tongues of pigs prepared
according to OECD TG 428. The full-
thickness skin membrane (FTS)
obtained from the upper half part of the
pig-ear’s back, which contains no
adipose tissue.
To mimic the in-use conditions when
cosmetics are applied to human skin
slightly damaged mechanically, hair
follicles of every second FTS were
shaved. Wet intact FTS membrane was
traveled with a manual razor
(Wilkinson Sword Extra II, Solingen,
Germany) twice in the opposite direc-
tion of hair growth, and once in the
direction of growth. The pressure
exerted on FTS was similar to shaving.
250 ng/cm
2
of BB and 2500 ng/cm
2
of
CAF or 250 ng/cm
2
of PB and 2500 ng/
cm
2
of CAF were applied in one dose.
Diffusion was carried out during non-
occluded 24-h exposure (an infinite
dose) to simulate typical consumer
usage of leave-on cosmetics. After the
experiment, in order to remove a
residual dose, the surface of FTS was
carefully rinsed three times with 1 mL
of appropriate solvent (distilled water
for after-shave and facial cleanser,
isopropanol for O/W emulsion and
diethyl ether for W/O emulsion).
The highest amounts of both dyes
penetrated into the epidermis from
ethanol-based after-shave; for example
4.0 and 2.6 times higher for BB and
PB, respectively than from W/O
emulsion.
Shaving caused only a slight decrease
in thickness of FTS (approx. 1%) but
significant increase in the TEC values
(between 3.5 and 5.7-fold) compared
to intact FTS.
Subsequently, diffusion studies through
shaven skin showed permeation values
higher roughly 1.2-fold for after-shave,
1.3-fold for facial cleanser, 1.1-fold for
O/W emulsion and 1.8-fold for W/O
emulsion as through intact FTS
Chemicals used:
Triphenyl-methane dyes
Brilliant Blue and Patent
Blue and caffeine.
Conclusion:
The normal process of shaving
significantly increases the
potential of systemic avail-
ability of both dyes from
hydrophilic vehicles. This
finding is worrisome, taking
into account the frequency
of skin treatment after
shaving and depilation with
cosmetic products contain-
ing the dyes, perhaps during
the long years of life.
(continued )
DOI: 10.3109/15569527.2014.966109 Shaving effects on percutaneous penetration 339

Table 3. Continued
S. # Study Study design No. of subjects Method Results Comments
Experimental design
Three series of in vitro diffusion experi-
ments were carried out; first through
intact FTS and second through shaven
FTS (a dose: the model cosmetic
product); third through FTL (a dose:
the salivary solution), all separately for
BB and PB dye.
3 Turner
6
/Impact of shaving
and antiperspirant use on
the axillary vault
Randomized trial 9 participants
(8 females and
1 male)
Subjects were asked to shave both axillae
2 days prior to the study and apply no
underarm product on the day of the
study. One axilla (randomized to left or
right) was shaved immediately prior to
iontophoresis in both vault and fossa.
Sterile solution of 1% histamine dihy-
drochloride in a 2.5% methyl cellulose
hydrogel was delivered into the skin
using an electric current supplied by an
iontophoresis controller (Moor
Instruments Ltd, Axminster, U.K.).
Blood flow was measured using a dual-
chamber laser Doppler flow monitor
(Moor Instruments Ltd). Baseline flux
(blood flow) measurements were
monitored for 1 min, followed by a
50 mA electric cur rent for 10 s, fol-
lowed by a further monitoring for
5 min. On removal of the chambers,
transparent film was placed over the
area and the size of wheal and flare
were recorded.
Histamine iontophoresis of the axillary
vault and fossa resulted in an increase
in both flare and wheal in the shaved
axilla when compared with the
respective unshaved control. Results
provide evidence of this increased
sensitivity to histamine in shaved skin.
However, the flare in the fossa was
significantly greater than that observed
in the vault (p50.05), when both of
these sites were shaved (wheal was
also greater, although not
significantly).
Conclusion: response to his-
tamine iontophoresis in the
shaved axilla was greater
than that of the unshaved
(both flare and wheal), pro-
viding a further example of
the potential for shaving to
damage the epidermal bar-
rier. Histamine response in
the vault of the shaved axilla
was less than that in the
shaved fossa, which is pro-
posed to be due to the
thicker epidermis in the
vault affording some degree
of protection from the shav-
ing process.
4 Banerjee and Ritchel
11
/
Transdermal permeation
of vasopressin. I.
Influence of pH, con-
centration, shaving and
surfactant on in vitro
permeation
Clinical trial Female Sprague-
Dawley rats
(Harlan) of
10-20 weeks
of age
Female Sprague-Dawley rats (Harlan)
of 10-20 weeks of age were sacrificed
by overdose ether inhalation. The
skins, excised after light clipping of the
hair on the back with electric clippers
(Oster), were cleaned of subcutaneous
tissue and fat. The skin was mounted
on diffusion cells and used within an
hour.
Binding study: Full-thickness excised
rat skin was used. Epidermis was
separated from dermis by a previously
reported method. The sorption iso-
therm was determined by equilibration
of a measured weight of epidermis
with 1 ml known concentration of
radio-labeled vasopressin solution in a
shaker-bath for 3 h at 30 C. After
Shaving increased the flux (about 5 times)
and decreased the lag time of vaso-
pressin significantly when compared to
light clipping. Stripping (25 times),
which removes the stratum corneum
showed dramatic increase in VP skin
permeation.
This shows that shaving
damages the skin partially
and gives evidence to the
fact that the stratum cor-
neum is the main barrier to
permeation of vasopressin.
340 M. Hamza et al. Cutan Ocul Toxicol, 2015; 34(4): 335–343

equilibration, the epidermis was
digested with TS-1 tissue solubilizer
(Research Products International) and
analyzed by scintillation counting.
Duplicate samples were also taken
from the aqueous phase and analyzed.
The effect of shaving was studied by
shaving rat skin one day before the
study with a Remington Super Mesh
Electric Shaver (Model SM-100,
Remington Products Inc.) after preli-
minary clipping of the hair. The skin
was allowed to heal for 24 h (although
no visible damage was observed), and
excised. This was compared to strip-
ping, where the skin was stripped 25
times with cellophane tape (Scotch
Brand, 3 M) to remove stratum cor-
neum (Flynn et al.
18
). Concentrations
of vasopressin solution in the donor
phase were 46.8 g/ml (4/Ci/ml) for
clipped and shaved skin and 49.5/zg/ml
(4 tCi/ml) for stripped skin
5 Wester and Maibach
15
/
Percutaneous Absorption
in the Rhesus Monkey
Compared to Man
Clinical Trial Female rhesus
monkeys used
Female rhesus monkeys (Macaca
mulattu), trained for metabolic studies,
were used. For iv administration a
saline solution of the compounds was
slowly given in the cephalic vein. The
amount given was the same as was
topically applied, averaging approxi-
mately 5 PCi. Urine was then collected
in a metabolism cage. For topical
application the monkeys were placed
in a metabolic chair for the first 24 hr
of the study. The hands of the monkey
were secured to the sides of the chair to
avoid its wiping off the applied com-
pound. This was done by wrapping
shaved wrists with adhesive tape,
reinforced with a second layer of
filament tape (Scotch brand). By using
adhesive tape the hands were secured
but blood circulation was not interfered
with. Testosterone and hydrocortisone
were applied to the skin in acetone, and
benzoic acid applied in methanol. The
application dose of 0.25 ml was
applied with a pipette on to a pre-
marked area and the solvent quickly
evaporated by gentle blowing. Because
of variations in the specific activity it
The ventral forearm of the rhesus monkey
is not very hairy. The effect of shaving
the topical application site was tested
by lightly depilating the area with an
electric razor. The data shows that
there was no difference between
shaved and unshaved skin in the
percutaneous absorption of testoster-
one. Application to the shaved area was
easier and so electric razor-dipilated
skin was use.
(continued )
DOI: 10.3109/15569527.2014.966109 Shaving effects on percutaneous penetration 341

Table 3. Continued
S. # Study Study design No. of subjects Method Results Comments
was necessary to vary the total area of
application. However, the quantity of
compound applied was always 4 pug/
cm*. For the next 24 hr, urine was
collected in a container below the
metabolism chair. Then the site of
application was washed with soap and
water and the monkey returned to a
metabolism cage to continue the urine
collection.
6 Guo
14
/Lecithin vesicular
carriers for transdermal
delivery of cyclosporin
A (October 1999)
Clinical trial Kunming mice Kunming mice, 3–4 weeks old, weighed
18–22 g, were kept under normal
laboratory conditions. The hair of test
mice was carefully trimmed short with
a pair of scissors. To destroy the
integrity of stratum corneum, the other
group of mice was shaved with scraper.
The application area on the abdominal
skin was limited to 2 cm
2
. Flexible
Vesicles and conventional vesicles
were respectively administered and left
to dry out. Mice were respectively
sacrificed after 1, 2,4,6,8 and 12 h of
application. Serum conc. Followed the
same procedure of extraction was
detected by HPLC.
In vivo study showed that with the
application of flexible vesicles, serum
drug concentration of 53.4399. 24 ng/
ml was detected after 2 h of permeation
and amounted to 154.37927.15 ng/ml
6 h later (Figure 3). When the stratum
corneum of mouse skin has been
destroyed by shaving, flexible vesicles
transferred large amount of drug into
blood, up to 187.32953.21 ng/ml after
1 h of application and amounted to
364.51954.06 ng/ml 4 h later.
Conventional vesicles failed to deliver
measurable amount of drug into the
blood under normal skin condition.
342 M. Hamza et al. Cutan Ocul Toxicol, 2015; 34(4): 335–343

transferred by f lexible vesicles, up to 187.3 ± 53 ng/ml after
1 h of application and amounted to 364.5 ± 54 ng/ml 4 h later
(Figure 3). This indicates shaving has a profound effect on the
permeation of Cyclosporin A.
Lastly, Wester and Maibach
15
used female rhesus monkeys
trained for metabolic studies. For IV administration a saline
solution of the compounds was slowly given in the cephalic
vein. Amount given was the same as was topically applied.
Urine was then collected in a metabolism cage. For topical
application the monkeys were placed in a metabolic chair for
the first 24 h. Hands of the monkey were secured to the sides
of the chair to avoid its wiping off the applied compound.
Testosterone and hydrocortisone were applied to the skin.
Effect of shaving the topical application site of the ventral
forearm of rhesus monkey was tested by lightly depilating the
area with an electric razor. Results showed there was no
difference between electric razor shaved and unshaved skin
in the percutaneous absorption of testosterone (Figure 4).
Table 3 summarizes the contents of the various studies
discussed above.
Conclusion
Shaving is ubiquitous, millions of people shave every day.
Many of the areas that are shaved have additional chemical
exposure e.g.
(i) Disinfectants and antiseptics on operating tables.
(ii) After-shave tonic, lotions and balms.
(iii) Moisturizers.
Therefore, it is highly relevant to investigate the systemic
and chemical effects of the various chemicals that come in
contact with the shaven areas. Shaving also destroys barrier
integrity of stratum corneum, which adds to increased
penetration. It has an exaggerated response to itch perception
and erythema.
This article summarizes the minimal experimental data
available. Hence, it surpasses a simple interpretation. For
example, in the histamine iontophoresis study conducted by
Marti et al., a standard 47 h patch test showed that antiper-
spirant irritancy increased post shaving as compared to
unshaved skin suggesting that shaving alters rapid penetration
possibly through shunts. The experiment performed by
Lucova et al. also showed a statistically significant increase
in permeation of the dye Brilliant Blue (ethanol-based after-
shave) from 65 ± 8 to 89 ± 17 and the dye Patent
Blue (ethanol-based aftershave) from 82 ± 4 to 105 ± 30
compared from intact to shaven FTS (full thickness skin),
respectively. Whereas Wester’s urinary excretion experiment
does not demonstrate any increase in penetration following
shaving. Therefore, this effect could be a species/compound-
specific as human, rat and pig skin has increased permeability
for various substances post-shaving whereas rhesus monkey
skin exhibits no such effect of testosterone in Wester’s
experiment.
Intuitively, we suspect that any possible increase in
penetration from shaving would be obtained in long term
rather than acute effects; for instance, we know of no database
demonstrating acute toxicity following shaving.
Using current knowledge about percutaneous penetration,
this is a vastly underserved area which will benefit by further
research and re-evaluation of different methods of shaving,
e.g. clippers/electric shavers versus razor blades, examining
chemicals of various physiochemical properties, species,
shaving and pre- and post-shave methods as well as anatomic
sites, which in the end, will permit a general predictive theory
and pertinent interventions and risk assessment.
Declaration of interest
There is no conflict of interest to declare.
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DOI: 10.3109/15569527.2014.966109 Shaving effects on percutaneous penetration 343