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j. Soc. Cosmet. Chem., 34, 361-382 (November 1983) A comparative study of beard and scalp hair EVA TOLGYESI, D. W. COBLE, F. S. FANG, and E. O. KAIRINEN, Gillette Research Institute, 1413 Research Boulevard, Rockville, MD 20850. Received June 24, 1983. Presented at the Society of Cosmetic Chemists Annual Scientific Meeting, New York, New York, December 6-7, 1979. 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. INTRODUCTION The structure and physico-chemical properties of human hair are of great interest in relation to cosmetic processes applied to them. During the past twenty years, with the availability of electron microscopy and modern chromatographic techniques, great progress has been made in the characterization of the morphology (1-7), chemical composition and reactivity (8-12) of human scalp hair, and understanding effects of racial background on these properties (4-5, 12-14). Unfortunately, very few correspond- ing data are available about beard hair (14-17). A study was therefore conducted to elucidate differences in morphology, physical properties, chemical composition and reactivity between facial hair and scalp hair, utilizing, when possible, the beard and scalp fibers of the same individual and examining the hair of three racial groups: Caucasian, Chinese, and Negro. 361