104 JOURNAL OF COSMETIC SCIENCE lipid modifications. Jachowicz et al. (5) and Pande and Jachowicz (6) used fluorescence spectroscopy to quantify tryptophan photodecomposition after UV irradiation. They found that weathering caused hair to undergo a significant loss in tryptophan, as well as other chemical changes affecting keratin structure, such as the oxidation of disulfide bonds to cysteic acid. Deftandre et M. (7) investigated photoaging and photoprotection of natural hair using the FT-IR technique and found that water inside the hair fiber is a necessary prerequisite to photooxidation or photobleaching of hair during UV expo- sure. They concluded that natural melanin in the hair is, at most, a weak means of protecting hair against the photodegradative action of solar light. Giesen et M. (8) studied the hair protection behavior of different UV filters and found that broad- spectrum filters such as benzophenones were particularly effective in protecting hair against discoloration and against losses in fiber strength and breaking force. They also observed that an oil-based product such as a shine spray containing oil-soluble UV filter was more effective in UV protection than setting lotions, which contained water-soluble UV filters. Gonzenbach et M. (9) studied UV damage on human hair and compared ten different UV filters. Their findings suggest that the choice of UV filter and the careful optimization of the formulation are crucial in developing a final product that can protect human hair from solar UV effectively. They used a colorimetric method to analyze the content of tryptophan in the hair before and after UV irradiation. They also found that blond hair is more susceptible to UV damage than black hair. Korner et M. (10) studied changes in the content of 18-methyl eicosanoic acid (18-MEA) in wool after UV irra- diation. They found that exposing wool fabric to artificial sunlight resulted in a loss of approximately 45% of the original 18-MEA content and that the branched-chain fatty acid 18-MEA was more sensitive to UV irradiation than the saturated, straight-chain acids with 16 and 18 carbon atoms. Until now there have been very few published studies on UV damage in natural gray hair. Only one paper, from Hollfelder and his co-workers, studied the chemical and physical properties of pigmented and non-pigmented (gray) hair (11). They found no statistically significant differences between pigmented hair and gray hair in terms of their fiber ellipticity and fiber break strength (wet). However, they observed that the average diameter of gray hair was statistically larger than that of pigmented hair and that the cystine content in gray hair was less than that in pigmented hair. They reported that gray hair showed a significant decrease in both wet breaking strength and cystine content after irradiation. After short periods of oxidation treatment, the level of cysteic acid in gray hair was found to be slightly higher than that in pigmented hair. They concluded that, in most cases, non-pigmented hair became more damaged after weath- ering than pigmented hair. However, no details about the test methods were reported. This paper represents the results of our recent studies on the physicochemical properties of natural gray hair and the effects of UV irradiation on these properties with and without UV protection. The central diameters, central cross-sectional area, central el- lipticity, extent of transverse swelling, stress-to-break, and strain-to-break of gray and black hair fibers were measured to determine if there were statistical differences between these types of hair. Gray and black hair samples were obtained from the heads of individuals for comparison. The UV study itself consisted of treating natural gray and virgin brown hair tresses with various and simple shampoo systems, which contain either a conventional UV filter or a quaternized UV absorber. Then the hair samples were irradiated with UV light for fifteen or twenty consecutive days. The following param-

UV DAMAGE ON GRAY HAIR 105 eters were measured and used to determine the extent of hair damage and assess the relative effectiveness of the two UV filters in sun protection: hair color change, tryp- tophan damage, tensile strength, wet combing force, dynamic advancing contact angle, cuticle abrasion, and fiber swelling. MATERIALS AND TEST METHODS CHEMICALS The following chemicals were used: a. Octylmethoxycinnamate (OMC), Escalol 557, ISP Van Dyk Inc., Belleville, NJ b. Cinnamidopropyltrimonium chloride (CATC), Incroquat UV-283, Croda Inc., Par- sippany, NJ c. Ammonium laureth sulfate (ALS), Standapol EA-2, Henkel Corp., Hoboken, NJ d. Sodium lauryl sulfate (SLS), Standapol WAQ-SP, Henkel Corp., Hoboken, NJ HAIR SAMPLES Virgin dark brown and 90% natural gray hairs were purchased from International Hair Importers & Products Inc., Bellerose, NY. Four tresses each (about 3 grams) of natural gray and virgin brown hair were used for the UV study. Hair samples were also collected from the heads of four graying individuals (with no known history of chemical treat- ments). These hair fibers were separated manually into pigmented (black) and non- pigmented (gray) fibers for evaluations and comparisons to each other. TREATMENT OF HAIR SAMPLES Test hair tresses were washed with 5% ALS solution (hair/solution weight ratio -- 1/10) for three minutes and rinsed thoroughly under running tap water (-20øC) for three minutes at an approximate flow rate of 75 ml/sec. The tresses were then air-dried and labeled as tresses 1-4. Tress 1 was used as a control without any UV exposure. Tresses 2, 3, and 4 were treated with 10% SLS aqueous solutions containing 2% CATC, 2% OMC, and no sunscreen active, respectively. Tresses 2, 3, and 4 were soaked in their respective formulations for five minutes at 35øC at the start, and then every 24 hours thereafter. Following each treatment, the tresses were rinsed under running tap water (-20øC) for 30 seconds at the flow rate of about 75 ml/sec and then returned to an environmentally controlled chamber for further UV irradiation. IRRADIATION OF HAIR Four UV-B lamps (F20T12, Atlantic Ultraviolet Corp., Hauppauge, NY) were installed in an environmentally controlled chamber, which was set at a constant temperature of 27øC and a constant relative humidity of 65%. The hair tresses were positioned 10 cm from the UV lamps. Irradiation energies were determined using PMA UV-B and UV-A detectors (Solar Light Co. Inc., Philadelphia). The applied wavelength range and irra- diance were 280-320 nm, 0.14 mW/cm 2 for UV-B and 320-400 nm, 0.49 mW/cm 2 for