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

362 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS MATERIALS AND METHODS 1. Reagents All the chemcial reagents were Certified ACS Grade or higher purity. 2. Hair Sample Acquisition Samples of beard and scalp hair for microscopy and tensile determinations were collected from men (10 Caucasians, 6 Chinese, and 6 Blacks) who were 20 to 50 years old. The fibers were cut very close to the skin line beard hair was taken from the lower chin area and scalp hair from the rear crown of the head. For chemical characterizations the hair fibers of several individuals were pooled beards were contributed by ten Caucasian men and Caucasian scalp hair was purchased from DeMeo Brothers, New York. 3. Hair Sample Preparation a. Purification Specimens for microscopy and tensile work were purified by a half-hour immersion in 1% aqueous Triton © X-100 followed by repeated distilled water rinses and a half-hour immersion in ethanol. The fibers were then air dried at room temperature. Bulk hair samples (50 g batch) were purified via Soxhlet extractions with anhydrous ether (14 hours) and ethanol (7 hours). The hair was then air dried, immersed in 0.001 N HCI (2 hours), and rinsed repeatedly with large volumes of distilled water until the pH of the overnight rinse water was 5.0. b. Mounting of Hair Fibers The fibers were individually mounted either with double-coated transparent tape onto microscope slides or in glycerin on slides under a coverslip. c. Cross Sections of Fibers Cross sections of fibers (6-8 /zm thick) were cut with the Hardy Microtome and mounted in glycerin under a coverslip on microscope slides. 4. Light Microscopy An American Optical Microstar © Series 10 Microscope, equipped with a Polaroid © Land Camera, or Zeiss © Microscope Model 62119 with 10x and 40x polarizing objectives was used in determinations of the diameter, ellipticity, and cross-sectional area of hair fibers. a. Measurement of Fiber Diameter A specially constructed microscope stage was used which would accommodate tabbed single fibers which could be rotated 180 ø along the long axis of the fibers. Five beard and five scalp hair fibers from each of ten individuals were investigated. Fibers were examined at five sites along each sample. At each site, fibers were rotated