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

Abstract

BackgroundGenetic 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.ObjectiveTo investigate changing of integral hair lipids after ultraviolet (UV) irradiation in three human ethnic groups.MethodsWe 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.ResultsAfrican 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.ConclusionWe conclude that integral hair lipid may protect the hair against the UV light.

External lipid function in ethnic hairs

“…The external lipids of the African hair fibers contain the greatest amount of apolar lipids with a consequently lesser amount of free fatty acids and polar lipids, whereas Caucasian and particularly Asian extracts contain a much greater amount of FFA and polar lipids, which is in accordance with Ji et al (Table ).…”

“…Furthermore, analyzed Afro‐American hair does not exhibit this same hair lipid effect; the level of lipids is much lower, which contradicts earlier studies . Ji et al presented analogous lipid composition in hair beyond groups. However, Asian hair was found to possess relatively more free fatty acids in the hair lipids which could be associated with their stronger protection to UV.…”

Lipid loses and barrier function modifications of the brown‐to‐white hair transition

“…These effects were primarily related to the lipid amounts and the order within the cuticle region. Changes in the lipid quantity or composition could modulate the dynamics of water in the fibre and thereby generate regions with distinct resistance …”

Alopecias Due to Drugs and Other Skin and Systemic Disorders

“…Other possible causes have been associated with TE, such as UV radiation on the hair; seasonal changes (i.e. peak incidence from July to October); crash diets; iron deficiency; and triggers like contact sensitizers, such as hair dyes, which lead to lipid, keratin, and melanin damage, promoting apoptosis and ultimate hair loss [11][12][13][14][15][16][17][18][19]. For diagnosis, detailed interrogation is required.…”