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Hair Shaft Damage from Heat and Drying Time of Hair Dryer

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Hair dryers are commonly used and can cause hair damage such as roughness, dryness and loss of hair color. It is important to understand the best way to dry hair without causing damage. The study assessed changes in the ultra-structure, morphology, moisture content, and color of hair after repeated shampooing and drying with a hair dryer at a range of temperatures. A standardized drying time was used to completely dry each hair tress, and each tress was treated a total of 30 times. Air flow was set on the hair dryer. The tresses were divided into the following five test groups: (a) no treatment, (b) drying without using a hair dryer (room temperature, 20℃), (c) drying with a hair dryer for 60 seconds at a distance of 15 cm (47℃), (d) drying with a hair dryer for 30 seconds at a distance of 10 cm (61℃), (e) drying with a hair dryer for 15 seconds at a distance of 5 cm (95℃). Scanning and transmission electron microscopy (TEM) and lipid TEM were performed. Water content was analyzed by a halogen moisture analyzer and hair color was measured with a spectrophotometer. Hair surfaces tended to become more damaged as the temperature increased. No cortex damage was ever noted, suggesting that the surface of hair might play a role as a barrier to prevent cortex damage. Cell membrane complex was damaged only in the naturally dried group without hair dryer. Moisture content decreased in all treated groups compared to the untreated control group. However, the differences in moisture content among the groups were not statistically significant. Drying under the ambient and 95℃ conditions appeared to change hair color, especially into lightness, after just 10 treatments. Although using a hair dryer causes more surface damage than natural drying, using a hair dryer at a distance of 15 cm with continuous motion causes less damage than drying hair naturally.
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Hair Shaft Damage from Heat and Drying Time of Hair Dryer
Vol. 23, No. 4, 2011 455
Received January 27, 2011, Revised May 16, 2011, Accepted for
publication May 30, 2011
Corresponding author: Won-Soo Lee, M.D., Department of Derma-
tology and Institute of Hair and Cosmetic Medicine, Yonsei Univer-
sity Wonju College of Medicine, 162 Ilsan-dong, Wonju 220-701,
Korea. Tel: 82-33-741-0622, Fax: 82-33-748-2650, E-mail: leewonsoo@
yonsei.ac.kr
T
his is an Open Access article distributed under the terms of the
Creative Commons Attribution Non-Commercial License (http:/
/
creativecommons.org/licenses/by-nc/3.0) which permits unrestricted
non-commercial use, distribution, and reproduction in any medium,
provided the original work is properly cited.
Ann Dermatol Vol. 23, No. 4, 2011 http://dx.doi.org/10.5021/ad.2011.23.4.455
ORIGINAL ARTICLE
Hair Shaft Damage from Heat and Drying Time of Hair
Dryer
Yoonhee Lee, M.D., Youn-Duk Kim1, Hye-Jin Hyun1, Long-quan Pi, Ph.D., Xinghai Jin,
Won-Soo Lee, M.D.
Department of Dermatology and Institute of Hair and Cosmetic Medicine, Yonsei University Wonju College of Medicine, Wonju, 1Central
Research Laboratory, Aekyung Industrial Inc., Daejeon, Korea
Background: Hair dryers are commonly used and can cause
hair damage such as roughness, dryness and loss of hair
color. It is important to understand the best way to dry hair
without causing damage. Objective: The study assessed
changes in the ultra-structure, morphology, moisture content,
and color of hair after repeated shampooing and drying with
a hair dryer at a range of temperatures. Methods: A stan-
dardized drying time was used to completely dry each hair
tress, and each tress was treated a total of 30 times. Air flow
was set on the hair dryer. The tresses were divided into the
following five test groups: (a) no treatment, (b) drying without
using a hair dryer (room temperature, 20oC), (c) drying with
a hair dryer for 60 seconds at a distance of 15 cm (47oC), (d)
drying with a hair dryer for 30 seconds at a distance of 10 cm
(61oC), (e) drying with a hair dryer for 15 seconds at a
distance of 5 cm (95oC). Scanning and transmission electron
microscopy (TEM) and lipid TEM were performed. Water
content was analyzed by a halogen moisture analyzer and
hair color was measured with a spectrophotometer. Results:
Hair surfaces tended to become more damaged as the
temperature increased. No cortex damage was ever noted,
suggesting that the surface of hair might play a role as a
barrier to prevent cortex damage. Cell membrane complex
was damaged only in the naturally dried group without hair
dryer. Moisture content decreased in all treated groups
compared to the untreated control group. However, the
differences in moisture content among the groups were not
statistically significant. Drying under the ambient and 95oC
conditions appeared to change hair color, especially into
lightness, after just 10 treatments. Conclusion: Although
using a hair dryer causes more surface damage than natural
drying, using a hair dryer at a distance of 15 cm with
continuous motion causes less damage than drying hair
naturally. (Ann Dermatol 23(4) 455462, 2011)
-Keywords-
Hair damage, Hair dryer, Heat, Natural ambient dry
INTRODUCTION
Diverse causes of extrinsic hair shaft damage have been
documented, and can be roughly divided into physical
causes and chemical causes1. Chemical causes include
bleaching, hair dyeing and perming. Frequent use of
chemical agents is a major cause of damage to the hair
shaft. When cosmetic products are used incorrectly or too
frequently, they may produce changes in hair texture that
correspond to morphological changes on the hair
surface2-7. Physical causes of hair shaft damage include
friction from hair accessories, washing, and towel drying.
Friction is a major damage factor of the hair surface,
especially in wet hair, although other factors, such as
photodamage and daily grooming may also lead to hair
damage. Exposure to ultraviolet radiation damages hair
fibers and sunlight can lead to dryness, rough surface
texture, decreased color and luster, and increased stiffness
and brittleness1,8.
Y Lee, et al
456 Ann Dermatol
Fig. 1. Illustration of transpiration moisture.
Hair dryers, which are commonly used for drying hair,
also can cause hair damage. The patterns of heat damage
caused by hair dryers have been investigated9-12. Yet, the
best way to dry hair without damage remains unclear.
The purpose of this study was to observe changes in the
ultra-structure, morphology, moisture content, and color
of hair after repeated shampooing and drying with a hair
dryer at a range of temperatures (natural ambient temperature,
47oC, 61oC, and 95oC), drying distances, and drying times.
MATERIALS AND METHODS
Hair
Chemically untreated hair was obtained from De Meo
Brothers (New York, USA). The hair was washed using 1%
(w/w) sodium dodecyl sulfate, and then thoroughly rinsed
with tap water and dried. We selected 20 cm long hairs
from the root weighing 2 g.
Hair treatme nts
Sodium lauryl sulfate (pH 6.0) diluted 1-in-10 was used for
shampooing, and a model UN-1324B commercial hair
dryer (Unix Electronics, Seoul, Korea) was used for
drying. We aimed to simulate daily hair care in our
experiments. In daily hair care practice, the drying
temperature from hair dryer is different because of the
distance between hair and hair dryer. Therefore, we
After shampooing, eused different distances (5, 10, and 15
cm) between hair samples and the hair dryer. The
temperature was measured 0.5 cm from the sample
surface.ach hair sample was tapped gently with a towel to
remove water drops. The roots were fixed to the plate and
the air flow was set on the hair dryer. Each treatment was
performed once a day, repeated treatments were done
after 24 h. Shampooing and drying treatments were
repeated 30 times for 30 days. We previously checked time
to dry completely for each treatment group, so the tresses
were divided into the following five test groups: (a) no
treatment, (b) shampooing and drying without using a hair
dryer (room temperature, 20oC), (c) shampooing and
drying with a hair dryer for 60 seconds at a distance of 15
cm (47oC), (d) shampooing and drying with a hair dryer for
30 seconds at a distance of 10 cm (61oC), and (e)
shampooing and drying with a hair dryer for 15 seconds at
a distance of 5 cm (95oC).
Measurements
Each measurement was performed 24 h after the last
treatment.
1) Scanning electron microscopy (SEM)
The prepared hair (5 cm-long from the root) was fixed
onto a specimen stub and sputter-coated with gold. The
hair was then inserted into a LEO 1499AP scanning
electron microscope (LEO, Oberkochen, Germany) operating
at an accelerating voltage of 30 kV for viewing and
photography.
2) Transmission electron microscopy (TEM)
Hair was placed in propylene oxide for 15 min. After
preparation with a 11 propylene oxideEpon mixture
overnight, the hair was embedded in an Epon mixture.
Horizontal sections approximately 6070 nm in thickness
were cut and stained with uranyl acetate and lead citrate.
The specimens were viewed with a JEM-1200EDXII trans-
mission electron microscope (JEOL, Tokyo, Japan) operating
at an accelerating voltage of 80 kV.
3) Lipid TEM
Hair was fixed in Karnovsky solution (2% glutaral-
dehyde2% paraformaldehyde) and rinsed in 0.1 M
sodium cacodylate and post-fixed with Lee's fixative
(0.5% RuO42% OsO40.2 M cacodylate buffer = 1
11) at room temperature for 90 min. This procedure was
designed to minimize hair injury and to better view the
lipid layer of the hair. Then, each section was dehydrated
in alcohol solutions substituted with propylene oxide, and
embedded in the Epon mixture. The embedded section
was double stained with uranyl acetate and lead citrate.
Sections were examined as described for TEM.
4) Hair water content
Water content was analyzed by a HG53 halogen moisture
analyzer (Mettler Toledo, Zürich, Switzerland). Individual
tresses were cut to 1 cm in size and individually preserved
in 82% relative humidity desiccators for 7 days before
Hair Shaft Damage from Heat and Drying Time of Hair Dryer
Vol. 23, No. 4, 2011 457
Fig. 2. Hair surface damage measured by scanning electron
microscopy after the hair drying process. The extent of damage
to hair surfaces increased as the temperature rose. Treatments:
(A) no treatment, (B) shampooing and drying without using a hair
dryer (room temperature, 20oC), (C) shampooing and drying with
a hair dryer for 60 seconds at a distance of 15 cm (47oC), (D)
shampooing and drying with a hair dryer for 30 seconds at a
distance of 10 cm (61oC), (E) shampooing and drying with a hair
dryer for 15 seconds at a distance of 5 cm (95oC).
analyzing moisture content. A fragment of hair (300 mg, 1
cm in length) was placed on the saucer of the balance,
and the change in weight during heating was recorded
every 30 sec. The hair sample was heated for the first 40
min at 65oC, which is assumed to be the temperature of
most hair dryers, and for the next 30 min at 180oC to
evaporate all water. As shown in Fig. 1, the first
converging point (A) was observed between 30 and 40
min after heating started, and the second converging point
(B) was observed between 60 and 70 min after heating
started. Based on the difference in weight between A and
B, the second transpiring moisture content (variation of
water content, %) was calculated according to the
following equation: (A/AB)×100, where A is the water
content of sample after the elapsed time and B is the water
content of virgin hair in each condition.
Y Lee, et al
458 Ann Dermatol
Fig. 3. Cuticle layer damage measured by transmission electron
microscopy after the hair drying process. The outer-most cuticle
layer is damaged only during the 95oC drying process. Treatments
were as described in Fig. 1.
5) Color change
Hair color change was measured with a model CM-3550
spectrophotometer (Konica Minolta, Tokyo, Japan) scanning
a spectral range from 360 to 740 nm in 20 nm steps. The
equipment rendered CIELab values of L* (lightness), a*
(red/green color axis), and b* (yellow/blue color axis). From
these values, and following ASTM D 22440-85, the
calculated color difference parameters were L* (light-
ness difference: lighter if positive, darker if negative),
a* (red/green difference: redder if positive, greener
if negative), b* (yellow/blue difference: yellowish if
positive, bluer if negative), and E* (total color
difference, E*ab=[(L*)2(a*)2(b*)2]½). The
Hair Shaft Damage from Heat and Drying Time of Hair Dryer
Vol. 23, No. 4, 2011 459
Fig. 4. Cortex layer measured by transmission electron micro-
scopy after the hair drying process. In all conditions, there were
no signs of damage. Treatments were as described in Fig. 1.
hair samples were measured in sets of 10.
RESULTS
Hair surface damage
Hair surface damage was examined by SEM after repeated
shampooing and drying. Lifting or cracks were not evident
in the untreated and naturally dried groups (Fig. 2A and B).
In the 47°C-treated group, multiple longitudinal cracks
were observed in the cuticle (Fig. 2C). More obvious lifting
and cracks of the cuticle were noted in the 61oC-treated
group (Fig. 2D). The most severe damage of the cuticle
was observed in the 95oC-treated group, with many cracks,
holes, and hazy cuticle borders being evident (Fig. 2E).
Y Lee, et al
460 Ann Dermatol
Fig. 5. Cell membrance complex (CMC) damage measured by
lipid transmission electron microscopy after the hair drying
process. Only the naturally dried group showed bulging of the
CMC layer. Treatments were as described in Fig. 1. The
arrowhead indicates bulging portions in the intercellular lipid
layers.
Hair cuticle and cortex
Damage to the cuticle and cortex of the hair was
investigated by TEM after repeated shampooing and
drying. Compared with the untreated group (Fig. 3A), no
noticeable changes were observed in naturally dried hair
and the low-temperature dried hair (Fig. 3BD). How-
ever, punched-out cuticles were seen in the 95oC-treated
group (Fig. 3E). In terms of cortex damage, there were no
signs of damage in any group (Fig. 4). All cortex compart-
ments, including melanin granules and cortical cells, were
well preserved in all treated groups compared with the
untreated group.
Hair Shaft Damage from Heat and Drying Time of Hair Dryer
Vol. 23, No. 4, 2011 461
Fig. 6. Results of moisture content analysis. Treated groups had
lower moisture contents than the untreated group, which were
not statisticall
y
si
nificant.
Table 1. Color changes under variable conditions
Group
Before treatment Treatment, 10 times Treatment, 30 times
L* a* b* L* L* a* a* b* b* EL*L* a* a* b* b* E
b 15.89 2.29 2.66 17.20 1.31 2.42 0.13 2.76 0.1 1.32 17.51 1.62 2.70 0.41 2.87 0.21 1.68
c 16.56 2.47 2.77 16.42 0.14 2.36 0.11 2.37 0.4 0.44 17.05 0.49 2.73 0.26 3.17 0.4 0.68
d 16.06 2.21 2.25 16.55 0.49 2.49 0.28 2.74 0.49 0.74 17.16 1.1 2.81 0.6 3.33 1.08 1.65
e 15.51 2.26 2.39 17.75 2.24 2.39 0.13 2.58 0.19 2.25 17.87 2.36 2.69 0.43 3.08 0.69 2.49
L*: lightness, a*: red to green color axis, b*: yellow to blue color axis, L*: difference of lightness between before and after treatment,
a*: difference of red to green color axis difference between before and after treatment, b*: difference of yellow to blue color
axis between before and after treatment, E : total color difference between before and after treatment, b: shampooing and drying
without using a hair dryer (room temperature, 20oC), c: shampooing and drying with a hair dryer for 60 seconds at a distance of
15 cm (47oC), d: shampooing and drying with a hair dryer for 30 seconds at a distance of 10 cm (61oC), e: shampooing and drying
with a hair dryer for 15 seconds at a distance of 5 cm (95oC).
Cell membrane complex (CMC)
Damage to the CMC was examined by lipid TEM after the
repeated shampooing and hair drying process. Only the
naturally dried group exhibited the bulging that is the sign
of a damaged CMC (Fig. 5B). The CMC was well
preserved with no signs of damage in control and all of
the hair dryer groups (Fig. 5A, CE).
Moisture content analysis
Treated tresses were conditioned in a constant 82%
relative humidity desiccator for 7 days and moisture
content was analyzed by a halogen moisture analyzer. The
changes in moisture content are summarized in Fig. 6.
Treated groups, both with and without mechanical hair
drying, displayed decreased moisture content com-
pared to the untreated group (4.6%). The moisture con-
tent was a little lower at 47oC and 61oC compared to
95oC and natural drying. However, the differences
between the treatment groups (group be) were not
statistically significant. Also, differences between the
control group and all treatment groups were not signi-
ficant.
Color changes
Table 1 shows the changes in color under all con-
ditions. Drying under the ambient and 95oC conditions
appeared to change hair color, especially into lightness,
after just 10 treatments. In all treated groups, the hair
was brighter than its original condition after 30
repeated cycles.
DISCUSSION
The human hair shaft consists of the cortex with a central
axial medulla and an external cuticular layer13. Hair
damage due to heat can be found on the surface, cuticle
layers, and possibly the CMC. In previous studies, common
dailygrooming procedures caused more damage to the
endocuticle and CMC than to other hair components4,9.
Repeated cycles of wetting and blow-drying can cause
multiple cracks on hair cuticles9. Other studies reported
damagecaused by curling irons10,14. Hair shampoo
surfactants and daily hair drying (including heat drying)
causes damage to the ultrastructure of the hair, as well as
color changes15.
In this study, we evaluated changes to the ultra-structure,
morphology, moisture content, and color of hair after
repeated shampooing and drying at various temperatures
(natural ambient temperature, 47oC, 61oC, and 95oC). We
tried to simulate daily hair care practice, so we could
suggest a pro per method to dry hair. Although the
temperature of hair dryer is fixed, the temperature rises as
the distance between hair and hair dryer decreases.
Hair drying without a hair dryer produced a relatively well
Y Lee, et al
462 Ann Dermatol
protected hair surface, while hair that was dried using a
hair dryer showed more damage of hair surfaces. In
addition, the hair surfaces showed an overall tendency to
become more damaged as the temperature increased,
with the most severe surface damage produced after
drying with the highest temperature (95oC). No cortex
damage was noted in any group, suggesting that the
surface of the hair might play a role as a barrier to prevent
cortex damage. The cortex might be more damaged with
increased repetition of the process, when the barrier of
hair surface is broken. The CMC was damaged only in the
naturally dried group. This result was quite unexpected,
because increased temperatures generally led to more hair
damage. It took over 2 h to dry the hair tress completely
under ambient conditions. The hair shaft swells when in
contact with water, as does the delta-layer of the CMC.
The delta-layer is the sole route through which water
diffuses into hair16, and so we speculate that the CMC
could be damaged when it is in contact with water for
prolonged periods. Longer contact with water might be
more harmful to the CMC compared to temperature of
hair drying. Moisture content decreased in all treated
groups (with and without the hair dryer) compared to the
untreated control group. However, the differences
between the groups were not statistically significant. The
methods used to dry wet hair might not affect moisture
content. With regard to color, the hair became lighter after
repeated shampooing and drying. Drying under ambient
temperatures and at 95oC resulted in earlier changes in
hair color (after just 10 treatments). The reason why the
hair color is brighter after repeated shampooing and
drying is unknown. On TEM examination, no decrease of
melanin granules was found. However, after repeated
shampooing and drying, definite damage to hair cuticle
was evident on SEM examination. Therefore, we assume
that the hair color change might be because of the
damage to hair. Further study is needed to explain the
reasons for hair color changes.
Natural drying, exposure to ambient temperature after
gently remove dripping water drops with towel, is usually
considered to be safer than using a hair dryer. However,
damage to the CMC was noted only in the naturally dried
group and earlier changes in hair color were seen in this
group and the 95oC group. This effect of natural drying
has not been studied or described before. It is conceivable
that a long lasting wet stage is as harmful as a high drying
temperature (and may be even more dangerous to the
CMC). Further evaluation about contact time with water or
wet environment and hair damage is needed.
Although using a hair dryer caused more surface damage
than natural drying, the results of this study suggest that
using a hair dryer at a distance of 15 cm with continuous
motion causes less damage than drying hair naturally.
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Hairdryers are commonly known to cause hair damage such as “roughness”, “dryness”, and “hair color loss”. while using it. So, numerous studies have tried to find ways to dry hair with no damage or minimized level. In this study, we examined hair damage levels by varying drying applications during the process and analyzed hair changes either in essential characteristics such as “oil and moisture balance” or “microstructure”. As a result, hair was severely damaged when treated with a general hot air dryer for 90 minutes, causing cuticle crack or layer separation. In contrast, the plasma hairdryer caused just a little or even no damage to hair for the same exposure time. It may be because ions and moisture molecules generated when using a plasma hairdryer can protect hair structure from the harsh hot air condition.
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Background Hair fibers may be either oriented in a common direction or randomly arranged. Fiber arrangement as well as cosmetic treatment control the sensorial perception. The present study explores the respective influence of these two aspects by predicting the product performance in terms of tactile perception. Materials and Methods Friction forces between hair swatches of different curl patterns using a finger‐like probe have been measured to better mimic real‐life hair/finger contact. Measurements of fiber alignment, hair diameter (thickness), and compression tests were performed on natural and treated swatches to assess the respective weight of these parameters. Results Conditioned hair exhibit an adhesive behavior measured at the start of the frictional movement. Conversely, natural hair is influenced by fiber reorientation. After a few seconds, friction‐related signals stabilize. Thus, the averaged friction forces do not only depend on hair thickness, but increase with a decreased alignment of the fibers. Conclusions Intrinsic (diameter/curliness) and external (orientation/ friction/compression) characteristics allow to define a model of "macroscopic" roughness linked to the sensorial characterization. As friction of hair swatches depends upon fiber alignment and coating, this combined approach is potentially a very useful in vitro test, as an alternative or complementary method to sensory tests.
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The effects of thermal treatments on human hair induced by conventional curling irons, operating in the temperature range from 130°C to 164°C, have been investigated. The fibers were thermally exposed by continuous heating for extended periods of time (5-15 min) or by short (15 s) intermittent heating cycles. The model calculations of heat transfer through a fibrous assembly, based on heat conduction through a semi-infinire solid, were performed. The calculated data have shown that near-uniform temperature distributions are reached in the hair samples within a few seconds of thermal exposure, suggesting that continuous and intermittent modes of treatment are equivalent. The resulting damage to the fibers has been investigated and quantified by the use of fluorescence spectrophotometry, Hunter colorimetry, and combing analysis. The fluorescence analysis has shown that thermal treatment results in a decomposition of hair chromophores, specifically tryptophan (Trp) and its oxidation products (kynurenines). The calculated first-order rate coefficients of Trp decomposition were in the range from 0.03 to 0.12 (min 1), with an estimated activation energy of 6.6 kcal/mol. Hunter colorimetry was employed to quantify thermally induced color changes in hair, such as an increase in the yellowness of white and Piedmont hair or simultaneous yellowing and darkening of bleached hair. Combing analysis has revealed a gradual increase, as a function of exposure time, in combing forces that were measured in the tress sections exposed to curling irons. The extent of the combing increase was found to be dependent on the mode of thermal treatment in which intermittent heating cycles, separated by rinsing, resulted in a higher degree of fiber damage.
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Cycles of wetting and blow-drying were applied to hair fibers and resulted in the formation of multiple cracks on the hair cuticles. The peculiarity of these cracks was that they always appeared aligned parallel to the longitudinal axis of the hair fiber. The cracks appeared to be initiated at the end of the cuticles close to the cortex and propagated invariably towards the outer cuticle edges. The maximum growth length of each crack was seen to be limited to the size of one cuticle. Crack formation did not only occur at the outer edges of the cuticles but also took place in the second and third overlaid hidden cuticle sections. The results show that these cracks form when the external portions of the cuticles undergo drastic reduction in their hydration water. Under these conditions the outer cuticle portions become rigid and brittle and crack by the action of circumferential tension stresses arising from the swelling pressure of both the cuticle layers underneath and the cortex itself. Hair cuticle analysis from a panel of 100 individuals showed that these cracks are present in the hair of people who commonly blow-dry their hair and appear to a much lesser extent in the hair of subjects who do not practice this type of grooming process. The combing of hair fibers presenting this type of cracking was seen to result in the breakage of large portions of cuticle. The effect of some cosmetic actives on the formation of these cracks is also discussed.
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The relation between hair ultra-structure damages and color changes was studied. Virgin dark-brown hair was hand-washed, using lauryl sodium sulfate solution in 40 °C water, rinsed, wet-combed, heat-dried and dry-combed for up to 120 times. Ultra-structure changes were studied by electron microscopy. The treatments damage the cuticle and the cortex. The extraction of soluble material renders cavities, or holes, in the endocuticle. The cavities are 50–200 nm in diameter. There are two kinds of cavities: some filled with lower density material than the remaining endocuticle and some filled with air or water vapor. Displacement, cracking and cleavage of cuticle cells are also observed. Cuticle removal was found to proceed in two ways: via cleavage through the cell membrane complex, and via endocuticle rupture, taking place preferentially in the cavities’ surroundings. In the cortex, cavities develop in the intermacrofibrilar cement, in the cell membrane complex and around the melanin granules. These ultra-structural damages give rise to significant changes on hair color, as shown by diffuse reflectance spectrophotometry. The hair lightness was found to increase after soft washing treatments (5–20 washes), or after keeping it in 40 °C water. Deeper hair degradation turns the hair lightness undistinguishable from the initial value, but changes the color mainly by a yellowing of the hair. A simple model based on light reflection was developed to explain hair reflectance behavior before and after damage; results show a reasonable agreement with the experimental data.
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We have developed a method for preparing artificially damaged hairs, similar to those generally observed in permed hair. Moreover, we have established two models of hair for testing preventive ingredients. A model for scale lift was prepared using alkaline protease digestion following lyophilization. A model for splitting, was prepared by successive extraction of the cortical protein, re-oxidation, and lyophilization. The practical application of these models was confirmed through the evaluation of the preventive effect of a polymer or peptides.
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J. Cosmet. Sci., 60, 437–465 (July/August 2009) The structure, chemistry and physical properties of the cell membrane complex (CMC) of keratin fibers are reviewed, highlighting differences in the three types of CMC. Starting with Rogers’ initial description of the CMC in animal hairs, several important developments have occurred that will be described, adding new details to this important structure in mammalian hair fibers. These developments show that essentially all of the covalently bound fatty acids of the beta layers are in the cuticle and exist as monolayers. The beta layers of the cortex are bilayers that are not covalently bonded but are attached by ionic and polar linkages on one side to the cortical cell membranes and on the other side to the delta layer. The delta layer between cortical cells consists of five sublayers; its proteins are clearly different from the delta layer that exists between cuticle cells. The cell membranes of cuticle cells are also markedly different from the cell membranes of cortical cells. Models with supporting evidence are presented for the three different types of cell membrane complex: cuticle–cuticle CMC, cuticle–cortex CMC, and cortex–cortex CMC.
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Integral hair lipid (IHL) is bound to the keratinized cell surface to make an environmentally resistant lipid envelope. It is mainly positioned on the hair cuticle and inner root sheath. IHL in the hair follicle may regard as hair barrier to be similar to the epidermal lipid layer functioning as skin barrier. Major constituents of IHL are fatty acid, phytosphingosine, ceramide in decreasing order. Minor constituents of IHL are cholesterol, cholesterol sulfate and cholesterol oleate. Cuticle or cortical cell surface in hair are abundant in fatty acids unlike the keratinized area of epidermis or sebaceous gland, and about 30-40% of such fatty acids are composed of 18-methyl-eicosanoic acid which is known to be bound to proteins by ester or thioester bond. Various factors including moisture, solvent, oxidative damage during bleaching or permanent waving affect IHL. Photochemical changes also can occur in IHL as well as in hair protein and hair pigment. Lipid metabolism is thought to play an essential role in lipid envelope of hair, but also involvement in hair development and function.
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The structure, chemistry and physical properties of the cell membrane complex (CMC) of keratin fibers are reviewed, highlighting differences in the three types of CMC. Starting with Rogers' initial description of the CMC in animal hairs, several important developments have occurred that will be described, adding new details to this important structure in mammalian hair fibers. These developments show that essentially all of the covalently bound fatty acids of the beta layers are in the cuticle and exist as monolayers. The beta layers of the cortex are bilayers that are not covalently bonded but are attached by ionic and polar linkages on one side to the cortical cell membranes and on the other side to the delta layer. The delta layer between cortical cells consists of five sublayers; its proteins are clearly different from the delta layer that exists between cuticle cells. The cell membranes of cuticle cells are also markedly different from the cell membranes of cortical cells. Models with supporting evidence are presented for the three different types of cell membrane complex: cuticle-cuticle CMC, cuticle-cortex CMC, and cortex-cortex CMC.
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The rational evaluation of hair disorders requires familiarity with follicular anatomy. Hair structure can be easily examined by studying clipped hair shafts, entire hairs gently pulled or forcibly plucked from the scalp, and scalp biopsies (sectioned vertically or transversely). Anatomic features will be different depending on whether a given hair is in the anagen, catagen, or telogen phase. Follicle size will also vary, from the minute vellus hair to the long, thick terminal hair. Each follicle can be divided into distinct regions--bulb, suprabulbar zone, isthmus, and infundibulum. Activity growing (anagen) hairs are characterized by a hair matrix surrounding a dermal papilla; inner and outer root sheaths are present and well developed. A catagen hair can be identified by its markedly thickened vitreous layer and fibrous root sheath, which surrounds an epithelial column; above this column, the presumptive club forms. A telogen hair is distinguished by its fully keratinized club, which is surrounded by an epithelial sac. Below this lies the secondary hair germ and condensed dermal papilla, waiting for the mysterious signal that initiates a new life cycle.
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Following investigation of two individuals with bubble hair abnormality, a reproducible cause has been established. Simple experiments showed that brief, focal heating of damp hair is sufficient to cause bubbles to form inside the hair fibres. This in turn results in weak, dry and brittle hair which breaks easily.