UV DAMAGE ON GRAY HAIR 117 Fig. 10-a Tress 1 (No UV) Fig. 10-b Tress 2 (CATC) Fig. 10-c Tress 3 (OMC) Fig. 10-d Tress 4 (SLS) Figure 10. SEM pictures of hair fibers after 1000 combing strokes. Table II UV Damage on Gray and Dark Brown Hair* Gray hair Dark brown hair Tress Tress Tress Tress Tress Tress 2 3 4 2 3 4 Hair treatment CATC OMC SLS CATC OMC SLS Stress-to-break retention (%) 92.1 82.1 75.7 96.6 88.6 81.1 Tryptophan damage (%) 4.17 79.17 85.42 4.5 80.2 85.2 Difference in color (AE) 0.74 5.56 7.42 0.72 3.89 4.45 * Data collected for gray hair after 15 days of UV irradiation and for dark brown hair after 20 days of UV irradiation. From the data in Table II it can be concluded that gray hair is more sensitive to UV irradiation and undergoes more severe damage than dark brown hair. These results clearly demonstrate that gray hair needs additional protection from UV exposure. CONCLUSIONS It has been shown that there are no statistically significant differences in the center maximum diameter, center cross-sectional area, center ellipticity, extent of swelling, stress-to-break, and strain-to-break between gray and black hair from the same heads

118 JOURNAL OF COSMETIC SCIENCE (Table I). However, UV irradiation causes more severe damage on natural gray hair than on natural dark brown hair (Table II). The extent of UV damage can be assessed by the following measurements: a change in hair color (color fading or yellowing), a decrease in tensile strength (Young's modulus and stress-to-break), a decrease in dynamic advancing contact angle, a loss of tryptophan at the hair surface, and an increase in hair swelling in 0.1 N NaOH solution. It has been found that the quaternized UV absorber, cinna- midopropyltrimonium chloride (CATC), delivered from a simple rinse-off shampoo system, is more substantive on hair and more effective in protecting hair from UV damage than a conventional UV filter. CATC not only provides excellent UV protection for hair, but provides conditioning benefits as well. ACKNOWLEDGEMENTS The authors acknowledge Kevin Gallagher's encouragement and Dr. Rob Comber's invaluable help and discussions during the whole study. REFERENCES (1) S. Ramapandian, S. B. Warner, and Y. K. Kamath, Photodegradation of human hair,J. Cosmet. Sd., 49, 309-320 (1998). (2) E. Hoting, M. Zimmermann, and S. Hilterhaus-Bong, Photochemical alterations in human hair, I. Artificial irradiation and investigations of hair proteins,J. Soc. Cosmet. Chem., 46, 85-99 (1995). (3) E. Hoting and M. Zimmermann, Sunlight-induced modifications in bleached, permed, or dyed human hair, J. Soc Cosmet. Chem., 48, 79-91 (1997). (4) E. Hoting, M. Zimmermann, and S. Hilterhaus-Bong, Photochemical alterations in human hair. II. Analysis of melanin, J. Soc Cosmet. Chem., 46, 181-190 (1995). (5) J. Jachowicz, M. Helioff, and C. Rocafort, Photodegradation of hair and its photoprotection by a substantive photofilter, DCI, 28-44 (December 1995). (6) C. Pande and J. Jachowicz, Hair photodamage--Measurement and prevention, J. Soc. Cosmet. Chem., 44, 109-122 (1993). (7) A. Deftandre, J. Garson, and E. Leroy, Photoaging and photoprotection of natural hair, 16th IFSCC Congress, New York, October 8-11, 1990, pp. 197-208. (8) Giesen et al., UV filter for hair protection, 16th IFSCC Congress, New York, October 8-11, 1990, pp. 294-314. (9) H. Gonzenbach, W. Lohncock, K.-F. De Polo, V. G. Givaudan, G. Blankenburg, J. FiShles, H. HiScker, and K. Schiifer, UV damage on human hair: A comparative study with 10 UV-filters, 19th IFSCC Congress, Sydney, 1996, pp. 41-52. (10) A. Korner, H. Schmidt, Th. Merten, St. Peters, H. Thomas, and H. H/Scker, Changes in the content of 18-methylicosanoic acid in wool after UV-irradiation and corona treatment, 9th International Wool Textile Research ConJ•rence, pp. 414-419. B. Hollfelder, G. Blankenberg, L. Wolfran, and H. Hocker, Chemical and physical properties of pigmented and non-pigmented hair ("grey hair"), Int. J. Cosmet. Sci., 17, 87-89 (1995). K. Roper and E. Finnimore, Chemical structure of chromophores formed during photoyellowing of wool, Int. Wool Text. Res. Conf, Tokyo, 1985, Vol. 4, pp. 21-31. E. Leroy, A. Deftandre, and J. Gatson, Photoaging of human hair, 7th International Hair Science Symposium, Bad-Vevenahr, 1990. J. Cegarra and J. Gacen, A method of determining the amount of tryptophan in wool by hydrolysis with sulphuric acid for short periods,JSDC, 215-220 (April 1968). (11) (12) (13) (14)