102 JOURNAL OF COSMETIC SCIENCE (15) P. Corcuff, C. Hadjur, C. Chaussepied, and R. Toledo-Crow, Confocal laser microscopy of the in vivo human skin revisited, SPIE Proc., 3605, 73-81 (1999). (16) C. Bertrand and P. Corcuff, In vivo spario-temporal visualization of the human skin by real-time confocal microscopy, Scanning, 16, 150-154 (1994). (17) M. Rajadhyaksha, S. Gonz&lez, J. M. Zavislan, R. R. Anderson, and R. H. Webb, In vivo confocal laser scanning microscopy of human skin. II: Advances in instrumentation and comparison with histology, J. Invest. Dermatol., 113, 293-303 (1999). (18) N. Kobayashi, A. Nakagawa, T. Muramatsu, Y. Yamashina, T. Shirai, M. W. Hashimoto, Y. Ishigaki, T. Ohnishi, and T. Mori, Supranuclear melanin caps reduce ultraviolet induced DNA photoproducts in human epidermis,J. Invest. Dermatol., 110, 806-810 (1998). (19) T. B. Fitzpatrick, M. Miyamoto and K. Ishikawa, The evolution of concepts of melanin biology, Arch. Dermatol., 96, 305-323 (1965). (20) A.J. Thody, Epidermal melanocytes: Their regulation and role in skin pigmentation, Ear. J. Dermatol., 5,558-565 (1995). (21) M. R. Chedekel, "Photophysics and Photochemistry," in Melanin: Its Role in Human Photoprotection, L. Zeise, M. R. Chedekel, and T. B. Fitzpatrick, Eds. (Valdenmar Publishing Co, Overland Park, KS, 1995), pp. 11-22. (22) O. Yamamoto and J. Bhawan, Three modes of melanosomes transfer in Caucasian facial skin: Hy- pothesis based on an ultrastructural study, Pigment Cell Res., 7, 156-169 (1994). (23) R. R. Anderson and J. A. Parrish, The optics of human skin, J. Invest. Dermatol., 77, 13-19 (1981). (24) R.J. Scheuplein, A survey of some fundamental aspects of the absorption and reflection of light by tissue, J. Soc. Cosmet. Chem., 15, 111-122 (1964). (25) A.D. Pearse, S. A. Gaskell, and R. Marks, Epidermal changes in human skin following irradiation with either UVA or UVB,J. Invest. Dermatol., 88, 83-87 (1987). (26) R.M. Lavker, G. F. Gerberick, D. Veres, C.J. Irwin, and K. H. Kaidbey, Cumulative effects from repeated exposures to suberythemal doses of UVB and UVA in human skin, J. Am. Acad. DermatoL, 32, 53-62 (1995). (27) A. R. Young, The sunburn cell, Photo-Dermatol., 4, 127-134 (1987). (28) R. Linse and G. Richard, Histology of UV-induced epidermis reactions. 1. A contribution to the differentiation of sunburn cells, Dermatologishe MonatsschriJ}, 176, 345-348 (1990). (29) C. Bayerl, S. Taake, I. Moll, and E.G. Jung, Characterization of sunburn cells after exposure to ultraviolet light, Photodermatol. PhotoimmunoL Photomed., 11, 149-154 (1995). (30) N. Kollias, "The Spectroscopy of Human Melanin Pigmentation," in Melanin: Its Role in Human Photoprotection, L. Zeise, M.R. Chedekel, and T.B. Fitzpatrick, Eds. (Valdenmar Publishing Co, Overland Park, KS, 1995), pp. 31-38. (31) J. Borovansky, P. Hach, K. Smetana Jr., M. Elleder, and I. Matous-Malbohan, Attempts to induce melanosome degradation in vivo, Folia Biologica (Praha), 45, 47-52 (1999).

Cosmet. Sci., 52, 103-118 (March/April 2001) Ultraviolet damage on natural gray hair and its photoprotection TAO GAO and ANN BEDELL, Croda Inc., North American Technical Center, 180 Northfield Avenue, Edison, NJ 08837. Accepted for publication February 28, 2001. Synopsis The physicochemical properties of natural gray hair obtained from the heads of individuals and as well as commercial samples were investigated. No statistically significant differences were observed in terms of their central maximum diameter, central cross-sectional area, central ellipticity, average tensile strength, and average extent of transverse swelling between gray and black hair. The correlation between the elongation and the contraction of the cross-sectional area of hair fibers during extension was established as a statistically linear function, with a coefficient of 0.758. The damage on natural gray hair from ultraviolet (UV) irradiation were assessed by measuring the following parameters: hair color, Young's modulus, stress-to- break, wet combing force, dynamic advancing contact angle, tryptophan damage, cuticle abrasion, and transverse swelling of hair fiber in 0.1 N NaOH solution. It has been found that gray hair undergoes more severe UV damage and needs more UV protection than dark brown hair. Experimental results indicate that the quaternized UV absorber, cinnamidopropyltrimonium chloride (CATC), delivered from a simple sham- poo system, is more substantive on hair and more effective in protecting hair from UV damage than a conventional UV filter. CATC also provided an additional conditioning benefit on hair. INTRODUCTION The influence of sunlight and ultraviolet (UV) light on both untreated and cosmetically treated human hair has been studied extensively by a number of researchers. Recently Ratnapandian et al. (1) studied the role of moisture in the photolysis of melanin-free virgin Piedmont hair and presented a free-radical mechanism to explain the photolysis processes. Changes in wet mechanical properties, swelling behavior, and IR spectrum were monitored and used to determine the degree of damage. The authors observed that hair exposed to UV irradiation sustains weathering damage under all conditions of relative humidity and found that exposure at 30% RH causes the least damage. Hoting and Zimmermann (2-4) studied photochemical alterations in human hair and sunlight- induced modifications in bleached, permed, and dyed-brown human hair. They mea- sured changes in hair color, tensile strength, and lipid compositions before and after irradiation with UV-A, UV-B, visible (VIS), and IR light. They found that blond hair is less photostable than black hair and that chemically treated hair exhibits significant color fading and yellowing after UV exposure. They also reported that chemically bleached hair needs additional protection against photochemically induced protein and 103