UV DAMAGE ON GRAY HAIR 115 16 lO 13.7 11.3 :.:.:. .:.:. . NO UV 11.7 ........ ...... :... :...:. C^TC OMC Hair Sample and Treatment Figure 8. Transverse swelling of hair fibers after UV irradiation. 15.5 .:.:.'.:: - ::::.'. ........ ::::::::::::::::::::::::: ........... : :7::'?:.: . .:...: :... ::..:.:..:.. ß .: ...:.:.-::-:.:... ß ::::::::::::::::::::: ..' '.' :-: .'.':'::: ß SLS degradation, and the protein residues were large enough to be retained. This only leads to osmotic swelling of fiber, which is smaller in magnitude than the diffusion swelling caused by the loss of protein fragments. TRYPTOPHAN DAMAGE In order to compare the tryptophan damage on the surface of hair, we measured fluo- rescence intensities of four test gray hair tresses using a Fluorolog-3 spectrophotometer from Spex with a solid-sample accessory. The excitation wavelength was set at 295 nm and the tryptophan emission intensity was measured at 340 nm. The percent tryptophan damage (Trp damage) was calculated as [(I o - Ia)/I o] x 100, where I a and I o represent, respectively, the tryptophan emission intensities from damaged hair and non-damaged hair (5). The emission intensity has been assumed to be directly proportional to the surface tryptophan concentration. The percent photoprotection was calculated as 1-Trp damage. The calculated Trp damage and percent photoprotection are presented in Figure 9. After 15 consecutive days of UV irradiation, the unprotected natural gray hair (tress 4) lost about 85% of its surface tryptophan content. Gonzenbach et al. (9) reported 26.4% to 37.6% decreases in tryptophan content of untreated blond hair after 180 hours of exposure to simulated sunlight. Cegarra and Gacen (14) reported that the tryptophan content in wool decreased about 61% after 100 exposure hours in a Fade-Ometer. Jachowicz et al. (5) have indicated that the fluorescence technique probes only the surface layers of hair and detects tryptophan damage related to the residues of this amino acid located in the cuticles and/or outermost layers of the cortex. They reported 45% tryp- tophan loss for Piedmont hair under outdoor solar irradiation for only 65 hours. Our

116 JOURNAL OF COSMETIC SCIENCE • •oo-t 13., 80 ½ 40 o i•1 Photoptotection, % i 95,83 4..17 ..... f111111lllllll # 2, CATC 85,42 19,1 ? # 3, OMS # 4, SLS Hair Sample Figure 9. Tryptophan damage and photoprotection of different hair tresses. experimental results are consistent with their studies. From. Figure 9, it is clear that CATC provides very effective protection from. tryptophan photodamage. CUTICLE ABRASION After UV irradiation, hair fibers from the four test gray hair tresses were taken and examined under SEM. No visible damage on the hair surface (cuticle appearance) was observed. In order to detect the structural damages in hair cuticles, we combed all these four test gray hair tresses with 1000 strokes using a combing wheel (one combing per second). After combing, we randomly collected hair fibers from these hair tresses and inspected them. under SEM to determine the extent of cuticle abrasion. Four typical SEM pictures are presented in Figure It is seen that hair fibers from. tresses 3 and 4 underwent more cuticle abrasion compared with those from tresses 1 and 2. These results indicated that more cuticle structural damages were taking place in tresses 3 and 4 than in tresses 1 and 2 during UV irradiation. This clearly demonstrates that the hair surface (cuticles) in tress 2 was protected by CATC from. a combination of mechanical and UV damage. COMPARISON OF UV DAMAGE IN GRAY VS. DARK BROWN HAIR Some of the UV damage data for gray and dark brown hair tresses are summarized in Table II to demonstrate the effects of pigmentation on UV damage.