A comparative study of beard and scalp hair
Eva Tolgyesi , D. W. Coble , F. S. Fang , E. O. Kairinen

Synopsis

A study was conducted to elucidate the differences in morphology, physical properties, chemical composition, and reactivity between facial hair and scalp hair, utilizing light and electron microscopy, tensile measurements, amino acid analyses, and reaction rates. The effect of ethnic background on fiber structure and geometry was also investigated. The beard and scalp hairs of all three ethnic groups (Caucasian, Chinese, and Negro) differed significantly in fiber morphology. Scalp fibers had smaller cross-sectional areas and were more rounded than beard fibers, which exhibited asymmetrical, oblong, and trilobal shapes. There were more cuticle layers, less ordered scale patterns, and more extensive medullation in beard hair than in scalp hair of the same subject. In addition, some ethnic differences were observed in fiber size, geometry, and pigmentation in both facial and scalp hair.

The principal difference in chemical composition was the lower disulfide content of beard hair. In addition, beard hair was richer in aspartic acid, lysine, and tyrosine and poorer in valine and serine. The higher disulfide content of scalp hair was reflected in greater resistance to solubilization by urea-bisulfite, slower swelling rate in formic acid, and less supercontraction or permanent set in bisulfite solutions than beard hair under identical conditions.

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