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Comparison of hair shaft damage after chemical treatment in Asian, White European, and African hair Yoonhee Lee1, MD, Youn-Duk Kim2, MD, PhD, Long-quan Pi1, MD, Sung Yul Lee1, MD, Hannah Hong1, MD, PhD, and Won-Soo Lee1, MD, PhD
1 Department of Dermatology and Institute of Hair and Cosmetic Medicine, Yonsei University Wonju College of Medicine, Wonju, South Korea, and 2Aekyung Industrial, Inc., Central Research Laboratory, Daejeon, South Korea
Abstract Background Diverse causes of extrinsic damage to the hair shaft have been documented and can be roughly divided into physical and chemical causes. Chemical causes of hair damage include bleaching, hair dyeing, and perming. Objectives The goal of this study was to investigate differences in patterns of serial damage in Asian, White European (WE), and African hair after chemical stress imposed by
Correspondence Won-Soo Lee, MD, PhD, Department of Dermatology Yonsei University Wonju College of Medicine 162 Ilsan-Dong Wonju 220-701 South Korea E-mail: [email protected] Funding: None. Conflicts of interest: None.
straightening and coloring treatments. Methods Hairs were divided into control and treatment groups (straightening, coloring, and a combination of straightening and coloring). At 24 hours after the final treatment, patterns of hair damage were evaluated using transmission electron microscopy (TEM) and lipid TEM. Grades of hair cuticle and cortex damage were evaluated by three dermatologists. Results In the TEM examination, the cuticle of Asian hair proved to be resistant to damage caused by straightening treatments, whereas the WE hair cuticle and cortex were relatively susceptible to stress imposed by coloring treatments. In the combination treatment of straightening and coloring, African hair emerged as the most resistant to stress. In the lipid TEM examination, no notable differences in cell membrane complex
doi: 10.1111/ijd.12247
damage were observed among the three groups of hairs. Conclusions The present study suggests that WE hair is relatively susceptible and African hair is more resistant to chemical stresses, such as those imposed by straightening and coloring.
Introduction Hair is a very important and distinctive feature that plays a major role in self-perception. To some extent, hair is used to express personality and personal image. The color of the human skin and the morphology of the hair differ among races, and genetic factors are the major causes of these differences. Many studies on skin differences among races have been published; however, studies of differences in hair by ethnicity began only with the increase in interest in cosmetics. Hair morphology is classified as straight, wavy, curly, woolly, or peppercorn.1 Straight hair is mainly observed in people of Asian and White European (WE) ethnicity, whereas curly or peppercorn hair is mainly observed in people of African ethnicity.2 Hair is also classified by ethnicity into Asian, WE, and African types.3 Studies of the differences in hair among races have been performed to confirm the morphologic and biochemical differences. Morphologic studies have mainly focused on hair color and shape and changes in response to exterª 2013 The International Society of Dermatology
nal stimulations and have been based primarily on electron microscope data. In Asian and WE hair, the surface cuticle layer of the hair maintains uniform patterns that determine the relatively smooth hair texture. In Africans, however, hair is twisted as it grows so that the cuticle layer is irregularly arranged and is easily damaged by physicochemical irritations, such as combing and shampooing.4 Asian hair has the largest mean diameter, followed by WE hair, whereas the cross-section of African hair is ovoid or kidney-shaped.5 With regard to mechanical properties, African hair has less tensile strength and breaks more easily than does WE hair. African hair has extremely curly configurations and is thus more difficult to comb than are hair types from other ethnic groups.3 Diverse causes of extrinsic damage to the hair shaft have been documented and can be roughly divided into physical and chemical causes.6 Physical causes of hair shaft damage include friction from hair accessories, washing, and towel drying. Friction is a major cause of damage to the hair surface, especially when the hair is wet, International Journal of Dermatology 2013
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Hair shaft damage after chemical treatment
Table 1 Hairs from three ethnic groups subgrouped by control group and chemical stressors Chemical stress (repetitions)
Ethnicity
Control
Straightening (31)
Straightening (33)
Coloring (31)
Coloring (33)
Straightening (31), coloring (31)
Asian White European African
As-0 WE-0 Af-0
As-S1 WE-S1 Af-S1
As-S3 WE-S3 Af-S3
As-C1 WE-C1 Af-C1
As-C3 WE-C3 Af-C3
As-S1C1 WE-S1C1 Af-S1C1
Figure 1 Hairs from three ethnic groups were divided into control and chemical stress subgroups. After straightening (S) and coloring (C), hair samples were found to have changed in shape and color
Table 2 Grades of hair cuticle layer and cortex damage observed with transmission electron microscopy Grade
Criteria
Grades of hair cuticle layer damage (Tcu) Tcu0 Intact cuticle layer ≥6 layers Tcu1 Outer cuticle detachment, cuticle ≥5 layers Tcu2 Tcu1 + bubbles in the endocuticle Tcu3 Remaining cuticle: 3 or 4 layers Tcu4 Remaining cuticle ≤2 layers Grades of hair cortex damage (Tco) Tco0 Intact CMC, no damaged melanin granules Tco1 Damage in the CMC (bubbles): confined to a depth of 500 nm Tco2 Damage in the CMC (bubbles): beyond a depth of 500 nm Tco3 Holes in the CMC or damage to the melanin granules
CMC, cell membrane complex. Source: Kim et al.10
although other factors, such as photodamage and daily grooming, may also lead to hair damage.7 Chemical causes of hair damage include bleaching, hair dyeing, and perming. The frequent use of chemical agents is a major cause of damage to the hair shaft. When cosmetic products are used incorrectly or too frequently, changes in hair texture corresponding to morphologic changes on the hair surface may result.8,9 In the present study, differences in patterns of serial damage among Asian, WE, and African hair after the imposition of chemical stressors, such as straightening and coloring treatments, were investigated. International Journal of Dermatology 2013
Figure 2 Hairs from the control groups (As-0, WE-0, Af-0) showed intact cuticles with more than six layers (Tcu0) and an intact cell membrane complex with no damaged melanin granules (Tco0). (Transmission electron microscopy; magnification 910,000) ª 2013 The International Society of Dermatology
Lee et al.
Figure 3 Cuticle damage in hairs after straightening (S) treatment. Asian hair cuticles were more resistant to straightening treatment than cuticles of hairs from the other two ethnic groups. White European (WE) and African hair cuticles showed similar patterns of damage after straightening. (Transmission electron microscopy; magnification 910 000)
Materials and methods Preparation of hair samples and chemical treatments Virgin hairs from three ethnic groups representing, respectively, Asian, WE, and African-American subjects, were purchased from De Meo Brothers, Inc. (New York, NY, USA). Hair samples representing each ethnic group were obtained from one healthy donor without any systemic illness or disease affecting scalp condition. All hairs were prepared as 2-g tresses of 15 cm in length. The tresses were cleaned by immersing them in a 300-ml, 5% sodium lauryl ether sulfate solution for five minutes and then rinsed under running distilled water for 30 seconds. Subsequently, the tresses were dried thoroughly in an ambient condition for 24 hours. Each of the three hair groups were subdivided into a control and five chemical stress groups (Table 1, Fig. 1). For hair straightening treatment, ammonium thioglycolate was applied to completely dry hair samples, which were then straightened with a comb. After combing, the samples were placed in a hot chamber at 65 °C for 10 minutes and then rinsed in running distilled water. The hair samples were lightly dried with a towel, and peroxide neutralizer was applied. The hair samples were straightened with a comb and placed in an ª 2013 The International Society of Dermatology
Hair shaft damage after chemical treatment
Report
Figure 4 Cuticle damage in hairs after coloring (C) treatment. White European (WE) hair cuticles were the most vulnerable to coloring treatment. African hair cuticles appeared more resistant to coloring than Asian and WE hair. (Transmission electron microscopy; magnification 910 000)
ambient condition for 15 minutes. The hair samples were then washed in running distilled water and dried in an ambient condition. The straightening treatment was conducted three times at 24-hour intervals over a period of three days in a subset of each group (As-S3, WE-S3, Af-S3). Hair coloring was performed with a commercial product (light brown color, Flower menTM; Somang Ltd, Seoul, South Korea) that was applied to the hair samples and rinsed off under running distilled water after 30 minutes. The hair samples were then dried in an ambient condition. Coloring treatments were performed three times at 24-hour intervals over three days in a subset of each ethnic hair group (As-C3, WE-C3, Af-C3). In the hair straightening and coloring combination groups (As-S1C1, WE-S1C1, Af-S1C1), hair straightening was performed first and followed 24 hours later by coloring.
Evaluation of the effects of chemical treatment At 24 hours after the final treatment, patterns of hair damage were evaluated using transmission electron microscopy (TEM), lipid TEM, and a halogen moisture analyzer.
TEM examination Transmission electron microscopy was performed to evaluate damage to the cuticle layer and cortex. International Journal of Dermatology 2013
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Hair shaft damage after chemical treatment
Figure 6 Cortex damage in hairs after straightening (S) treatment. Cortexes of hairs from all three ethnic groups showed similar patterns of damage. (Transmission electron microscopy; magnification 920 000)
Figure 5 Cuticle damage in hairs after a combination of straightening (S) and (C) coloring treatments. African hair cuticles appeared more resistant to combination treatment than Asian or White European (WE) hair cuticles. Asian and WE hair cuticles showed similar patterns of damage after the combination treatment. (Transmission electron microscopy; magnification 910 000)
in 0.1 M sodium cacodylate, and post-fixed with Lee’s fixative (0.5% RuO4 : 2% OsO4 : 0.2 M cacodylate buffer [1 : 1 : 1]) at room temperature for 90 minutes. This procedure was designed to minimize hair injury and to facilitate viewing of the lipid layer of the hair.10 Next, each section was dehydrated in an alcohol solution substituted with propylene oxide and embedded in the epon mixture. The embedded section was double-stained with uranyl acetate and lead citrate. The section was then analyzed using TEM (JEM-1200 EDXII, 80 kV; JEOL Ltd).
Hair was placed in propylene oxide for 15 minutes. After preparation with a propylene oxide : epon (1 : 1) mixture overnight, the hair was embedded in an epon mixture.
Grades of hair cuticle, cortex, and cell membrane complex damage We utilized the grading system introduced by Kim et al.10 to
Horizontal sections of approximately 60–70 nm in size were cut
grade hair cuticle and cortex damage. Three individual, blinded
and stained with uranyl acetate and lead citrate. The specimens
dermatologists evaluated the TEM electron micrographs
were viewed with a TEM (JEM-1200 EDXII, 80 kV; JEOL Ltd,
according to this grading system (Table 2). To grade damage to
Tokyo, Japan).
the cell membrane complex, we invented the “Lmc grade”, which referred to the number of areas of bulge in representative
Lipid TEM examination
lipid TEM electron micrographs (Lmc1 = one area of bulge in
Lipid TEM examination was performed to evaluate cell membrane complex damage. Hair was fixed in Karnovsky
lipid TEM; TEM 9 100 000).
solution (2% glutaraldehyde plus 2% paraformaldehyde), rinsed
from each group were used. Five electron micrographs were
International Journal of Dermatology 2013
For both TEM and lipid TEM examination, about 10 hairs
ª 2013 The International Society of Dermatology
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Hair shaft damage after chemical treatment
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Figure 7 Cortex damage in hairs after coloring (C) treatment. The cortex of African hair appeared more resistant to a single coloring treatment than those of Asian and White European (WE) hair. However, cortexes of hairs from all three ethnic groups showed similar patterns of damage in three coloring treatments. (Transmission electron microscopy; magnification 920 000)
taken from a single hair; thus about 50 electron micrographs were obtained in each control and treatment group. Representative electron micrographs were chosen when >80% of electron micrographs showed a similar pattern of damage.
Results Evaluation of cuticle layer damage according to TEM
Hairs from the control groups (As-0, WE-0, Af-0) showed intact cuticles composed of more than six layers (Tcu0; Fig. 2). In the straightening treatment, Asian hair cuticles were more resistant than hair cuticles within the other two groups, and WE and African hair cuticles showed similar patterns of damage (Fig. 3). In the coloring treatment, WE hair cuticles were most vulnerable to damage. African hair cuticles appeared to be more resistant to coloring than Asian and WE hair cuticles (Fig. 4). In the hair straightening and coloring combination group, African hair cuticles appeared to be more resistant ª 2013 The International Society of Dermatology
Figure 8 Cortex damage in hairs after a combination of straightening (S) and coloring (C) treatments. The cortex of African hairs appeared more resistant to the combination treatment than those of Asian or White European (WE) hairs. Cortexes of WE and Asian hairs showed similar patterns of damage after the combination treatment. (Transmission electron microscopy; magnification 920 000)
than Asian and WE hair cuticles. The WE and Asian hair cuticles showed similar patterns of damage after the combination treatment (Fig. 5). Evaluation of cortex damage according to TEM
Hairs from the control groups showed intact cell membrane complexes with no damaged melanin granules (Tco0; Fig. 2). International Journal of Dermatology 2013
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Figure 9 Cell membrane complex evaluation in the control (0) and coloring treatment (C) groups. Hairs from the control group showed intact intercellular lipid layers. Hairs from all ethnic groups tolerated the coloring treatment well. Only Asian hairs showed a bulged cell membrane complex (arrow, Lmc1) after three coloring treatments. (Lipid transmission electron microscopy; magnification 9100 000)
In the straightening treatment, the cortexes of hairs in all three ethnic groups showed similar patterns of damage (Fig. 6). In the coloring treatment, the African hair cortex appeared to be more resistant to a single color treatment than the Asian and WE hair cortexes. However, the cortexes of hairs in all three ethnic groups showed similar patterns of damage after the three-time coloring treatment (Fig. 7). In the combination treatment group, the African hair cortex appeared to be more resistant to damage than Asian and WE hair cortexes. The WE and Asian hair cortexes showed similar patterns of damage after the combination treatment (Fig. 8). Evaluation of cell membrane complex damage according to lipid TEM
Control hairs showed intact intercellular lipid layers, indicating that they all adequately tolerated the coloring treatment. Only the Asian hair showed a bulged cell membrane complex after the three-time coloring treatment (Lmc1; Fig. 9). Hairs from all three ethnic groups showed similar patterns of damage after the straightening and combination (straightening and coloring) treatments, with the treatment resulting in the most extensive cell membrane complex damage (bulging) of all chemical stressors in all three ethnic hair groups (Fig. 10). International Journal of Dermatology 2013
Discussion The tensile strength of a fiber is highly dependent on its cross-sectional size. Although Asian hair has a larger diameter and consequently a higher tensile strength than WE hair, these two types of hair exhibit very similar behaviors under stress. In terms of mechanical properties, African hair generally has less tensile strength and breaks more easily than either WE or Asian hair.11,12 To date, there is no rationale to explain this phenomenon because neither structural nor chemical composition differences among the three types of hair have been observed. However, several hypotheses based on morphologic and geometric considerations may provide an explanation of the mechanical characteristics; these refer to the natural constrictions along the fibers, the twisted shapes of the fibers, and the presence of microcracks or fractures in the fiber.4,13–15 Reportedly, Asian and WE hairs behave differently in response to mechanical aggressions, such as extension.16 Seshadri and Bhushan16 studied the cuticle surface while increasing strain and found that Asian hair showed fewer lifted cuticle edges compared with stressed WE hair. However, no data on differences by ethnicity in patterns of hair damage after chemical stresses such as ª 2013 The International Society of Dermatology
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Hair shaft damage after chemical treatment
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Figure 10 Cell membrane complex evaluation in the straightening (S) and combination (SC) treatment groups by lipid transmission electron microscopy (TEM). Hairs from all ethnic groups showed similar patterns of damage after straightening and combination (straightening and coloring) treatments. (TEM, 9100,000. Arrows point to bulges indicating damage to the cell membrane complex)
Table 3 Summary of grades of hair cuticle, cortex, and cell membrane complex damage in the treatment groups ascertained by transmission electron microscopy (TEM) Chemical stress (repetitions)
Ethnicity Asian
White European
African
Straightening (31)
Straightening (33)
Coloring (31)
Coloring (33)
Straightening (31), coloring (31)
Tcu2 Tco2 Lmc1 Tcu3 Tco2 Lmc0 Tcu3 Tco2 Lmc2
Tcu2 Tco2 Lmc2 Tcu3 Tco2 Lmc2 Tcu3 Tco2 Lmc2
Tcu1 Tco1 Lmc0 Tcu2 Tco2 Lmc0 Tcu0 Tco0 Lmc0
Tcu2 Tco2 Lmc1 Tcu3 Tco2 Lmc0 Tcu2 Tco2 Lmc0
Tcu3 Tco2 Lmc3 Tcu3 Tco2 Lmc2 Tcu2 Tco1 Lmc3
Tcu, damage to the hair cuticle ascertained in TEM; Tco, damage to the hair cortex ascertained in TEM; Lmc, average number of areas of bulge of the cell membrane complex ascertained in lipid TEM (TEM 9100,000).
coloring and straightening have been reported. Therefore, we investigated differences after coloring and straightening in three ethnic hair groups ex vivo. ª 2013 The International Society of Dermatology
To summarize the results of the present study, Table 3 shows the grades of hair cuticle, cortex, and cell membrane complex damage among the treatment groups. International Journal of Dermatology 2013
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In the straightening treatment, the cuticles of Asian hair showed greater resistance than did those of hairs from the other two ethnic groups. In the coloring treatment, the cuticles and cortices of WE hair were relatively susceptible to stress compared with those of the other two ethnic hair types. In the combination treatment of straightening and coloring, which was assumed to impose the most extensive stress of all the treatments, African hair was found to be the most resistant to stress. This is the opposite of the result we had expected. African hair is known to break more easily because it has less tensile strength than hairs from the other two ethnic groups. We have no explanation for this current result, but we suggest that repeated extensive chemical stress may have changed the hairs' own mechanical properties. Further study is required. In terms of cell membrane complex damage, African hair seems to be more resistant to straightening and to combination treatment; however, no notable differences among hairs from the three ethnic groups were observed. All three ethnic hair groups tolerated the coloring treatment relatively well and showed similar patterns of damage after the straightening and combination treatment. This study is limited by its small sample size. Therefore, no statistical analysis to prove the significance of differences among hairs from the different ethnic groups could be performed. It is also limited by the fact that the investigation was performed ex vivo with purchased hair and in an intense manner that hardly simulates real-life hair procedures in humans. Conclusions The present study suggests that WE hair is relatively susceptible and African hair is more resistant to chemical stresses, such as those imposed by straightening and coloring treatments. These findings are limited by the study's small sample size and its ex vivo experiment protocol. However, because data on the differences in responses to chemical stress among hairs from different ethnic groups are lacking, the present study may represent a springboard to further evaluation. References 1 Lantis SD, Pepper MC. Woolly hair nevus. Two case reports and a discussion of unruly hair forms. Arch Dermatol 1978; 114: 233–238.
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2 Chang BS. Fine structure of damaged hair shaft by daily treatment of heat for a beautiful face. Kor J Elect Micro 2003; 33: 215–222. 3 Franbourg A, Hallegot P, Baltenneck F, et al. Current research on ethnic hair. J Am Acad Dermatol 2003; 48 (Suppl.): 115–119. 4 Lindelof B, Forslind B, Hedlad MA, et al. Human hair form: morphology revealed by light and scanning electron microscopy and computer-aided three-dimensional reconstruction. Arch Dermatol 1988; 124: 1359–1363. 5 Menkart J, Wolfram LJ, Mao I. Caucasian hair, Negro hair and wool, similarities and differences. J Soc Cosmet Chem 1996; 17: 769–787. 6 Jeon SY, Pi LQ, Lee WS. Comparison of hair shaft damage after UVA and UVB irradiation. J Cosmet Sci 2008; 59: 151–156. 7 Santos Nogueira AC, Joekes I. Hair color changes and protein damage caused by ultraviolet radiation. J Photochem Photobiol B 2004; 74: 109–117. 8 Ahn HJ, Lee WS. An ultrastructural study of hair fiber damaged and restoration following treatment with permanent hair dye. Int J Dermatol 2002; 41: 88–92. 9 Bolduc C, Shapiro J. Hair care products: waving, straightening, conditioning, and coloring. Clin Dermatol 2001; 19: 431–436. 10 Kim YD, Jeon SY, Ji JH, et al. Development of a classification system for extrinsic hair damage: standard grading of electron microscopic findings of damaged hairs. Am J Dermatopathol 2010; 32: 432–438. 11 Syed A, Kuhajda A, Ayoub H, et al. African-American hair: its physical properties and differences relative to Caucasian hair. Cosmet Toiletries 1995; 110: 39–48. 12 Kamath YK, Hornby SB, Weigmann HD. Mechanical and fractographic behavior of negroid hair. J Soc Cosmet Chem 1984; 35: 21–43. 13 Gamez GM. Plastic yielding and fracture of human cuticles by cyclical torsion stresses. J Cosmet Sci 1999; 50: 69–77. 14 Draelos ZD. Understanding African-American hair. Dermatol Nurs 1997; 9: 227–231. 15 Kamath YK, Hornby SB, Weigmann HD. Effect of chemical and humectant treatments on the mechanical and fractographic behavior of Negroid hair. J Soc Cosmet Chem 1985; 36: 39–52. 16 Seshadri IP, Bhushan B. Effect of ethnicity and products on in situ tensile response and morphological changes of human hair characterized by atomic force microscopy. Acta Mater 2008; 56: 774–781.
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Comparison of hair shaft damage after chemical treatment in Asian, White European, and African hair Yoonhee Lee1, MD, Youn-Duk Kim2, MD, PhD, Long-quan Pi1, MD, Sung Yul Lee1, MD, Hannah Hong1, MD, PhD, and Won-Soo Lee1, MD, PhD
1 Department of Dermatology and Institute of Hair and Cosmetic Medicine, Yonsei University Wonju College of Medicine, Wonju, South Korea, and 2Aekyung Industrial, Inc., Central Research Laboratory, Daejeon, South Korea
Abstract Background Diverse causes of extrinsic damage to the hair shaft have been documented and can be roughly divided into physical and chemical causes. Chemical causes of hair damage include bleaching, hair dyeing, and perming. Objectives The goal of this study was to investigate differences in patterns of serial damage in Asian, White European (WE), and African hair after chemical stress imposed by
Correspondence Won-Soo Lee, MD, PhD, Department of Dermatology Yonsei University Wonju College of Medicine 162 Ilsan-Dong Wonju 220-701 South Korea E-mail: [email protected] Funding: None. Conflicts of interest: None.
straightening and coloring treatments. Methods Hairs were divided into control and treatment groups (straightening, coloring, and a combination of straightening and coloring). At 24 hours after the final treatment, patterns of hair damage were evaluated using transmission electron microscopy (TEM) and lipid TEM. Grades of hair cuticle and cortex damage were evaluated by three dermatologists. Results In the TEM examination, the cuticle of Asian hair proved to be resistant to damage caused by straightening treatments, whereas the WE hair cuticle and cortex were relatively susceptible to stress imposed by coloring treatments. In the combination treatment of straightening and coloring, African hair emerged as the most resistant to stress. In the lipid TEM examination, no notable differences in cell membrane complex
doi: 10.1111/ijd.12247
damage were observed among the three groups of hairs. Conclusions The present study suggests that WE hair is relatively susceptible and African hair is more resistant to chemical stresses, such as those imposed by straightening and coloring.
Introduction Hair is a very important and distinctive feature that plays a major role in self-perception. To some extent, hair is used to express personality and personal image. The color of the human skin and the morphology of the hair differ among races, and genetic factors are the major causes of these differences. Many studies on skin differences among races have been published; however, studies of differences in hair by ethnicity began only with the increase in interest in cosmetics. Hair morphology is classified as straight, wavy, curly, woolly, or peppercorn.1 Straight hair is mainly observed in people of Asian and White European (WE) ethnicity, whereas curly or peppercorn hair is mainly observed in people of African ethnicity.2 Hair is also classified by ethnicity into Asian, WE, and African types.3 Studies of the differences in hair among races have been performed to confirm the morphologic and biochemical differences. Morphologic studies have mainly focused on hair color and shape and changes in response to exterª 2013 The International Society of Dermatology
nal stimulations and have been based primarily on electron microscope data. In Asian and WE hair, the surface cuticle layer of the hair maintains uniform patterns that determine the relatively smooth hair texture. In Africans, however, hair is twisted as it grows so that the cuticle layer is irregularly arranged and is easily damaged by physicochemical irritations, such as combing and shampooing.4 Asian hair has the largest mean diameter, followed by WE hair, whereas the cross-section of African hair is ovoid or kidney-shaped.5 With regard to mechanical properties, African hair has less tensile strength and breaks more easily than does WE hair. African hair has extremely curly configurations and is thus more difficult to comb than are hair types from other ethnic groups.3 Diverse causes of extrinsic damage to the hair shaft have been documented and can be roughly divided into physical and chemical causes.6 Physical causes of hair shaft damage include friction from hair accessories, washing, and towel drying. Friction is a major cause of damage to the hair surface, especially when the hair is wet, International Journal of Dermatology 2013
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Hair shaft damage after chemical treatment
Table 1 Hairs from three ethnic groups subgrouped by control group and chemical stressors Chemical stress (repetitions)
Ethnicity
Control
Straightening (31)
Straightening (33)
Coloring (31)
Coloring (33)
Straightening (31), coloring (31)
Asian White European African
As-0 WE-0 Af-0
As-S1 WE-S1 Af-S1
As-S3 WE-S3 Af-S3
As-C1 WE-C1 Af-C1
As-C3 WE-C3 Af-C3
As-S1C1 WE-S1C1 Af-S1C1
Figure 1 Hairs from three ethnic groups were divided into control and chemical stress subgroups. After straightening (S) and coloring (C), hair samples were found to have changed in shape and color
Table 2 Grades of hair cuticle layer and cortex damage observed with transmission electron microscopy Grade
Criteria
Grades of hair cuticle layer damage (Tcu) Tcu0 Intact cuticle layer ≥6 layers Tcu1 Outer cuticle detachment, cuticle ≥5 layers Tcu2 Tcu1 + bubbles in the endocuticle Tcu3 Remaining cuticle: 3 or 4 layers Tcu4 Remaining cuticle ≤2 layers Grades of hair cortex damage (Tco) Tco0 Intact CMC, no damaged melanin granules Tco1 Damage in the CMC (bubbles): confined to a depth of 500 nm Tco2 Damage in the CMC (bubbles): beyond a depth of 500 nm Tco3 Holes in the CMC or damage to the melanin granules
CMC, cell membrane complex. Source: Kim et al.10
although other factors, such as photodamage and daily grooming, may also lead to hair damage.7 Chemical causes of hair damage include bleaching, hair dyeing, and perming. The frequent use of chemical agents is a major cause of damage to the hair shaft. When cosmetic products are used incorrectly or too frequently, changes in hair texture corresponding to morphologic changes on the hair surface may result.8,9 In the present study, differences in patterns of serial damage among Asian, WE, and African hair after the imposition of chemical stressors, such as straightening and coloring treatments, were investigated. International Journal of Dermatology 2013
Figure 2 Hairs from the control groups (As-0, WE-0, Af-0) showed intact cuticles with more than six layers (Tcu0) and an intact cell membrane complex with no damaged melanin granules (Tco0). (Transmission electron microscopy; magnification 910,000) ª 2013 The International Society of Dermatology
Lee et al.
Figure 3 Cuticle damage in hairs after straightening (S) treatment. Asian hair cuticles were more resistant to straightening treatment than cuticles of hairs from the other two ethnic groups. White European (WE) and African hair cuticles showed similar patterns of damage after straightening. (Transmission electron microscopy; magnification 910 000)
Materials and methods Preparation of hair samples and chemical treatments Virgin hairs from three ethnic groups representing, respectively, Asian, WE, and African-American subjects, were purchased from De Meo Brothers, Inc. (New York, NY, USA). Hair samples representing each ethnic group were obtained from one healthy donor without any systemic illness or disease affecting scalp condition. All hairs were prepared as 2-g tresses of 15 cm in length. The tresses were cleaned by immersing them in a 300-ml, 5% sodium lauryl ether sulfate solution for five minutes and then rinsed under running distilled water for 30 seconds. Subsequently, the tresses were dried thoroughly in an ambient condition for 24 hours. Each of the three hair groups were subdivided into a control and five chemical stress groups (Table 1, Fig. 1). For hair straightening treatment, ammonium thioglycolate was applied to completely dry hair samples, which were then straightened with a comb. After combing, the samples were placed in a hot chamber at 65 °C for 10 minutes and then rinsed in running distilled water. The hair samples were lightly dried with a towel, and peroxide neutralizer was applied. The hair samples were straightened with a comb and placed in an ª 2013 The International Society of Dermatology
Hair shaft damage after chemical treatment
Report
Figure 4 Cuticle damage in hairs after coloring (C) treatment. White European (WE) hair cuticles were the most vulnerable to coloring treatment. African hair cuticles appeared more resistant to coloring than Asian and WE hair. (Transmission electron microscopy; magnification 910 000)
ambient condition for 15 minutes. The hair samples were then washed in running distilled water and dried in an ambient condition. The straightening treatment was conducted three times at 24-hour intervals over a period of three days in a subset of each group (As-S3, WE-S3, Af-S3). Hair coloring was performed with a commercial product (light brown color, Flower menTM; Somang Ltd, Seoul, South Korea) that was applied to the hair samples and rinsed off under running distilled water after 30 minutes. The hair samples were then dried in an ambient condition. Coloring treatments were performed three times at 24-hour intervals over three days in a subset of each ethnic hair group (As-C3, WE-C3, Af-C3). In the hair straightening and coloring combination groups (As-S1C1, WE-S1C1, Af-S1C1), hair straightening was performed first and followed 24 hours later by coloring.
Evaluation of the effects of chemical treatment At 24 hours after the final treatment, patterns of hair damage were evaluated using transmission electron microscopy (TEM), lipid TEM, and a halogen moisture analyzer.
TEM examination Transmission electron microscopy was performed to evaluate damage to the cuticle layer and cortex. International Journal of Dermatology 2013
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Hair shaft damage after chemical treatment
Figure 6 Cortex damage in hairs after straightening (S) treatment. Cortexes of hairs from all three ethnic groups showed similar patterns of damage. (Transmission electron microscopy; magnification 920 000)
Figure 5 Cuticle damage in hairs after a combination of straightening (S) and (C) coloring treatments. African hair cuticles appeared more resistant to combination treatment than Asian or White European (WE) hair cuticles. Asian and WE hair cuticles showed similar patterns of damage after the combination treatment. (Transmission electron microscopy; magnification 910 000)
in 0.1 M sodium cacodylate, and post-fixed with Lee’s fixative (0.5% RuO4 : 2% OsO4 : 0.2 M cacodylate buffer [1 : 1 : 1]) at room temperature for 90 minutes. This procedure was designed to minimize hair injury and to facilitate viewing of the lipid layer of the hair.10 Next, each section was dehydrated in an alcohol solution substituted with propylene oxide and embedded in the epon mixture. The embedded section was double-stained with uranyl acetate and lead citrate. The section was then analyzed using TEM (JEM-1200 EDXII, 80 kV; JEOL Ltd).
Hair was placed in propylene oxide for 15 minutes. After preparation with a propylene oxide : epon (1 : 1) mixture overnight, the hair was embedded in an epon mixture.
Grades of hair cuticle, cortex, and cell membrane complex damage We utilized the grading system introduced by Kim et al.10 to
Horizontal sections of approximately 60–70 nm in size were cut
grade hair cuticle and cortex damage. Three individual, blinded
and stained with uranyl acetate and lead citrate. The specimens
dermatologists evaluated the TEM electron micrographs
were viewed with a TEM (JEM-1200 EDXII, 80 kV; JEOL Ltd,
according to this grading system (Table 2). To grade damage to
Tokyo, Japan).
the cell membrane complex, we invented the “Lmc grade”, which referred to the number of areas of bulge in representative
Lipid TEM examination
lipid TEM electron micrographs (Lmc1 = one area of bulge in
Lipid TEM examination was performed to evaluate cell membrane complex damage. Hair was fixed in Karnovsky
lipid TEM; TEM 9 100 000).
solution (2% glutaraldehyde plus 2% paraformaldehyde), rinsed
from each group were used. Five electron micrographs were
International Journal of Dermatology 2013
For both TEM and lipid TEM examination, about 10 hairs
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Hair shaft damage after chemical treatment
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Figure 7 Cortex damage in hairs after coloring (C) treatment. The cortex of African hair appeared more resistant to a single coloring treatment than those of Asian and White European (WE) hair. However, cortexes of hairs from all three ethnic groups showed similar patterns of damage in three coloring treatments. (Transmission electron microscopy; magnification 920 000)
taken from a single hair; thus about 50 electron micrographs were obtained in each control and treatment group. Representative electron micrographs were chosen when >80% of electron micrographs showed a similar pattern of damage.
Results Evaluation of cuticle layer damage according to TEM
Hairs from the control groups (As-0, WE-0, Af-0) showed intact cuticles composed of more than six layers (Tcu0; Fig. 2). In the straightening treatment, Asian hair cuticles were more resistant than hair cuticles within the other two groups, and WE and African hair cuticles showed similar patterns of damage (Fig. 3). In the coloring treatment, WE hair cuticles were most vulnerable to damage. African hair cuticles appeared to be more resistant to coloring than Asian and WE hair cuticles (Fig. 4). In the hair straightening and coloring combination group, African hair cuticles appeared to be more resistant ª 2013 The International Society of Dermatology
Figure 8 Cortex damage in hairs after a combination of straightening (S) and coloring (C) treatments. The cortex of African hairs appeared more resistant to the combination treatment than those of Asian or White European (WE) hairs. Cortexes of WE and Asian hairs showed similar patterns of damage after the combination treatment. (Transmission electron microscopy; magnification 920 000)
than Asian and WE hair cuticles. The WE and Asian hair cuticles showed similar patterns of damage after the combination treatment (Fig. 5). Evaluation of cortex damage according to TEM
Hairs from the control groups showed intact cell membrane complexes with no damaged melanin granules (Tco0; Fig. 2). International Journal of Dermatology 2013
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Hair shaft damage after chemical treatment
Figure 9 Cell membrane complex evaluation in the control (0) and coloring treatment (C) groups. Hairs from the control group showed intact intercellular lipid layers. Hairs from all ethnic groups tolerated the coloring treatment well. Only Asian hairs showed a bulged cell membrane complex (arrow, Lmc1) after three coloring treatments. (Lipid transmission electron microscopy; magnification 9100 000)
In the straightening treatment, the cortexes of hairs in all three ethnic groups showed similar patterns of damage (Fig. 6). In the coloring treatment, the African hair cortex appeared to be more resistant to a single color treatment than the Asian and WE hair cortexes. However, the cortexes of hairs in all three ethnic groups showed similar patterns of damage after the three-time coloring treatment (Fig. 7). In the combination treatment group, the African hair cortex appeared to be more resistant to damage than Asian and WE hair cortexes. The WE and Asian hair cortexes showed similar patterns of damage after the combination treatment (Fig. 8). Evaluation of cell membrane complex damage according to lipid TEM
Control hairs showed intact intercellular lipid layers, indicating that they all adequately tolerated the coloring treatment. Only the Asian hair showed a bulged cell membrane complex after the three-time coloring treatment (Lmc1; Fig. 9). Hairs from all three ethnic groups showed similar patterns of damage after the straightening and combination (straightening and coloring) treatments, with the treatment resulting in the most extensive cell membrane complex damage (bulging) of all chemical stressors in all three ethnic hair groups (Fig. 10). International Journal of Dermatology 2013
Discussion The tensile strength of a fiber is highly dependent on its cross-sectional size. Although Asian hair has a larger diameter and consequently a higher tensile strength than WE hair, these two types of hair exhibit very similar behaviors under stress. In terms of mechanical properties, African hair generally has less tensile strength and breaks more easily than either WE or Asian hair.11,12 To date, there is no rationale to explain this phenomenon because neither structural nor chemical composition differences among the three types of hair have been observed. However, several hypotheses based on morphologic and geometric considerations may provide an explanation of the mechanical characteristics; these refer to the natural constrictions along the fibers, the twisted shapes of the fibers, and the presence of microcracks or fractures in the fiber.4,13–15 Reportedly, Asian and WE hairs behave differently in response to mechanical aggressions, such as extension.16 Seshadri and Bhushan16 studied the cuticle surface while increasing strain and found that Asian hair showed fewer lifted cuticle edges compared with stressed WE hair. However, no data on differences by ethnicity in patterns of hair damage after chemical stresses such as ª 2013 The International Society of Dermatology
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Hair shaft damage after chemical treatment
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Figure 10 Cell membrane complex evaluation in the straightening (S) and combination (SC) treatment groups by lipid transmission electron microscopy (TEM). Hairs from all ethnic groups showed similar patterns of damage after straightening and combination (straightening and coloring) treatments. (TEM, 9100,000. Arrows point to bulges indicating damage to the cell membrane complex)
Table 3 Summary of grades of hair cuticle, cortex, and cell membrane complex damage in the treatment groups ascertained by transmission electron microscopy (TEM) Chemical stress (repetitions)
Ethnicity Asian
White European
African
Straightening (31)
Straightening (33)
Coloring (31)
Coloring (33)
Straightening (31), coloring (31)
Tcu2 Tco2 Lmc1 Tcu3 Tco2 Lmc0 Tcu3 Tco2 Lmc2
Tcu2 Tco2 Lmc2 Tcu3 Tco2 Lmc2 Tcu3 Tco2 Lmc2
Tcu1 Tco1 Lmc0 Tcu2 Tco2 Lmc0 Tcu0 Tco0 Lmc0
Tcu2 Tco2 Lmc1 Tcu3 Tco2 Lmc0 Tcu2 Tco2 Lmc0
Tcu3 Tco2 Lmc3 Tcu3 Tco2 Lmc2 Tcu2 Tco1 Lmc3
Tcu, damage to the hair cuticle ascertained in TEM; Tco, damage to the hair cortex ascertained in TEM; Lmc, average number of areas of bulge of the cell membrane complex ascertained in lipid TEM (TEM 9100,000).
coloring and straightening have been reported. Therefore, we investigated differences after coloring and straightening in three ethnic hair groups ex vivo. ª 2013 The International Society of Dermatology
To summarize the results of the present study, Table 3 shows the grades of hair cuticle, cortex, and cell membrane complex damage among the treatment groups. International Journal of Dermatology 2013
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Hair shaft damage after chemical treatment
In the straightening treatment, the cuticles of Asian hair showed greater resistance than did those of hairs from the other two ethnic groups. In the coloring treatment, the cuticles and cortices of WE hair were relatively susceptible to stress compared with those of the other two ethnic hair types. In the combination treatment of straightening and coloring, which was assumed to impose the most extensive stress of all the treatments, African hair was found to be the most resistant to stress. This is the opposite of the result we had expected. African hair is known to break more easily because it has less tensile strength than hairs from the other two ethnic groups. We have no explanation for this current result, but we suggest that repeated extensive chemical stress may have changed the hairs' own mechanical properties. Further study is required. In terms of cell membrane complex damage, African hair seems to be more resistant to straightening and to combination treatment; however, no notable differences among hairs from the three ethnic groups were observed. All three ethnic hair groups tolerated the coloring treatment relatively well and showed similar patterns of damage after the straightening and combination treatment. This study is limited by its small sample size. Therefore, no statistical analysis to prove the significance of differences among hairs from the different ethnic groups could be performed. It is also limited by the fact that the investigation was performed ex vivo with purchased hair and in an intense manner that hardly simulates real-life hair procedures in humans. Conclusions The present study suggests that WE hair is relatively susceptible and African hair is more resistant to chemical stresses, such as those imposed by straightening and coloring treatments. These findings are limited by the study's small sample size and its ex vivo experiment protocol. However, because data on the differences in responses to chemical stress among hairs from different ethnic groups are lacking, the present study may represent a springboard to further evaluation. References 1 Lantis SD, Pepper MC. Woolly hair nevus. Two case reports and a discussion of unruly hair forms. Arch Dermatol 1978; 114: 233–238.
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2 Chang BS. Fine structure of damaged hair shaft by daily treatment of heat for a beautiful face. Kor J Elect Micro 2003; 33: 215–222. 3 Franbourg A, Hallegot P, Baltenneck F, et al. Current research on ethnic hair. J Am Acad Dermatol 2003; 48 (Suppl.): 115–119. 4 Lindelof B, Forslind B, Hedlad MA, et al. Human hair form: morphology revealed by light and scanning electron microscopy and computer-aided three-dimensional reconstruction. Arch Dermatol 1988; 124: 1359–1363. 5 Menkart J, Wolfram LJ, Mao I. Caucasian hair, Negro hair and wool, similarities and differences. J Soc Cosmet Chem 1996; 17: 769–787. 6 Jeon SY, Pi LQ, Lee WS. Comparison of hair shaft damage after UVA and UVB irradiation. J Cosmet Sci 2008; 59: 151–156. 7 Santos Nogueira AC, Joekes I. Hair color changes and protein damage caused by ultraviolet radiation. J Photochem Photobiol B 2004; 74: 109–117. 8 Ahn HJ, Lee WS. An ultrastructural study of hair fiber damaged and restoration following treatment with permanent hair dye. Int J Dermatol 2002; 41: 88–92. 9 Bolduc C, Shapiro J. Hair care products: waving, straightening, conditioning, and coloring. Clin Dermatol 2001; 19: 431–436. 10 Kim YD, Jeon SY, Ji JH, et al. Development of a classification system for extrinsic hair damage: standard grading of electron microscopic findings of damaged hairs. Am J Dermatopathol 2010; 32: 432–438. 11 Syed A, Kuhajda A, Ayoub H, et al. African-American hair: its physical properties and differences relative to Caucasian hair. Cosmet Toiletries 1995; 110: 39–48. 12 Kamath YK, Hornby SB, Weigmann HD. Mechanical and fractographic behavior of negroid hair. J Soc Cosmet Chem 1984; 35: 21–43. 13 Gamez GM. Plastic yielding and fracture of human cuticles by cyclical torsion stresses. J Cosmet Sci 1999; 50: 69–77. 14 Draelos ZD. Understanding African-American hair. Dermatol Nurs 1997; 9: 227–231. 15 Kamath YK, Hornby SB, Weigmann HD. Effect of chemical and humectant treatments on the mechanical and fractographic behavior of Negroid hair. J Soc Cosmet Chem 1985; 36: 39–52. 16 Seshadri IP, Bhushan B. Effect of ethnicity and products on in situ tensile response and morphological changes of human hair characterized by atomic force microscopy. Acta Mater 2008; 56: 774–781.
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