Ann Dermatol.  2013 Feb;25(1):54-60. 10.5021/ad.2013.25.1.54.

The Ethnic Differences of the Damage of Hair and Integral Hair Lipid after Ultra Violet Radiation

• Ji JH
• Park TS
• Lee HJ
• Kim YD
• Pi LQ
• Jin XH
• Lee WS

• KMID: 2265971
• DOI: http://doi.org/10.5021/ad.2013.25.1.54

Abstract

BACKGROUND
Genetic factors account for the majority of differences in skin color and hair morphology across human populations. Although many studies have been conducted to examine differences in skin color across populations, few studies have examined differences in hair morphology.
OBJECTIVE
To investigate changing of integral hair lipids after ultraviolet (UV) irradiation in three human ethnic groups.
METHODS
We studied the UV irradiation induced hair damage in hairs of three human populations. UV irradiation had been performed with self-manufactured phototherapy system. Damaged hair samples were prepared at 12 and 48 hours after UVA (20 J/sec) and UVB (8 J/sec) irradiation. We evaluated the changes of hair lipid using scanning electron microscopy (SEM), transmission electron microscopy (TEM), lipid TEM and HP-TLC. After UV irradiation, hair surface damage was shown.
RESULTS
African hair showed more severe damage on hair surface than others. The lipid compositions across human populations were similar, but Asian hair had more integral hair lipids than other groups as a whole. Especially, free fatty acid contents were higher than other lipids. After UV irradiation, lipid contents were decreased. These patterns were shown in all human populations. Asian hair has more integral hair lipid than European or African hair. After UV irradiation, European and African hair samples exhibited more damage because they have less integral hair lipids. However, Asian hair samples have less damage.
CONCLUSION
We conclude that integral hair lipid may protect the hair against the UV light.

Keyword

Ethnic groups; Integral hair lipid; UV irradiation

MeSH Terms

Asian Continental Ancestry Group
Ethnic Groups
Hair
Humans
Microscopy, Electron, Scanning
Microscopy, Electron, Transmission
Phototherapy
Skin
Ultraviolet Rays
Viola

Figure

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  Fig. 1 The ultraviolet (UV) irradiator manufactured by the authors. UV light was controlled using the switch on the left upper side (yellow circle: UV lamps, red circle: cooling fan).

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  Fig. 2 Scanning electron microscopy findings for all hair samples. The greater the irradiation time, the greater the damage to the hair surface. Ultraviolet B (UVB) radiation resulted in more damage than UVA, and African hair showed the most damage to the hair surface.

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  Fig. 3 Conventional transmission electron microscopy findings for all hair samples. Ultraviolet B (UVB) irradiation resulted in more damage than UVA irradiation (red arrow). All three groups exhibited similar patterns of damage. However, the African hair exhibited weaker resistance to UV irradiation than the other groups, and the African hair also exhibited a decreased number of cuticle layers than the other groups (red two-way arrow).

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  Fig. 4 Lipid transmission electron microscopy findings for all hair samples. Ultraviolet (UV) irradiation resulted in swelling of the lipid layer (red arrow). However, there were no differences observed among groups after UV irradiation.

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  Fig. 5 High-performance thin-layer chromatography (HP-TLC) analysis of ultraviolet (UV) light irradiated hair samples. The Asian hair had more integral hair lipids than the other hairs. In particular, the free fatty acid content was higher than those of the other lipids. UV irradiation resulted in decreased lipid content, especially free fatty acids. (A) Amount of integral hair lipids between ethnic groups. (B) Integral hair lipids after UV radiation. S, standard; Control, #11, #21, #31; UVA 12 hr, #12, #22, #32; UVA 48 hr, #13, #23, #33; UVB 12 hr, #14, #24, #34; UVB 48 hr, #15, #25, #35.

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