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J. Soc. Cosmet. Chem., 48, 209-217 (July/August 1997) Effect of anti-keratin antibody on the nature of hair HIDEYO UCHIWA, Biochemistry Laboratory, Kanebo, Ltd., 3-28 Kotobuki-cho 5-chome, Odawara City 250, Japan. Accepted for publication September 30, 1997. Synopsis We investigated the effects of anti-keratin antibody obtained from the milk of cows immunized with human hair keratin (a) on the stretching of hair fibers via a tensile tester and (b) on fracture generation through excessive brushing. The binding ability of anti-keratin antibody to damaged hair was confirmed by using an enzyme-linked immunosorbent assay. The antibody increased the elastic modulus in the Hooken region and tensile strength at the breaking point of a damaged hair fiber. The antibody inhibited fracture generation of the permed hair, which had been brushed excessively. The F(ab')2 fragment of the antibody that has bivalent binding sites to keratin inhibited fracture generation in hair as well as did the intact antibody. On the other hand, the Fab fragment that has a single binding site did not show the effect of inhibiting fracture generation. These results indicate that the anti-keratin antibody having two binding sites to the keratin of hair increases resistance to stretching and inhibits damage to hair. INTRODUCTION Hair damage is the breakdown or removal of structural components or parts of hair that either weaken it or make it more vulnerable to the chemical or mechanical breakdown that occurs in everyday grooming actions. Sunlight, pool water, and cosmetic products such as perms, bleaches, straighteners, and some hair dyes chemically alter hair and increase its propensity to further chemical and mechanical breakdown, as evidenced by an increased sensitivity to cuticle abrasion/erosion and fiber splitting (1). Excessive combing and brushing result in stretching and further fracture generation in hair. Fracture patterns such as the step fracture and fibrillation are capable of producing split ends through the subsequent actions of combing and brushing (2). Collagen hydrolysate (3), ginseng saponin (4), and carboxymethyl chitin (5) have been reported to increase the tensile strength of hair fiber, and are used to treat hair. Hair cortical and cuticle cells are known to have keratin filaments as a cytoskeleton. In our previous study (6,7), we obtained the anti-keratin antibody through the immunization of cows with human hair keratin. The anti-keratin antibody demonstrated the ability to improve the tensile strength of damaged hair. The present study was undertaken in order to more precisely define the effect of the anti-keratin antibody on the stretching of hair fibers via a tensile tester and on fracture generation through excessive brushing. We show that the anti-keratin antibody in- 209