j. Soc. Cosmet. Chem., 48, 79-91 (March/April 1997) Sunlight-induced modifications in bleached, permed, or dyed human hair EDO HOTING, Hans Schwarzkopf GmbH, D-22763 Hamburg, Germany, and MONIKA ZIMMERMANN, Deutsches Wollforschungsinstitut an der RWTH, Aachen e.V., D-52062 Aachen, Germany. Synopsis The influence of sunlight on cosmetically pretreated human hair was systematically investigated. Thus, bleached, perreed, and dyed hairs were irradiated for four weeks with simulated sunlight, which was split into the specific ranges UV-B, UV-A, visible light (VIS), and IR. Subsequent color measurements, strength tests, and cholesterol determinations of untreated and irradiated samples showed characteristic degradation patterns in the melanin, protein, and lipid components of human hair. Comparison of the results with irradiated, untreated brown hair point to a synergistic effect between cosmetic treatments and sunlight. In particular, chemical bleaching increases a photochemically initiated brightening (VIS), loss in strength (UV-A), and degradation of cholesterol (VIS). INTRODUCTION The influence of sunlight on untreated human hair was extensively analyzed by exami- nation of the protein, melanin, and lipid components as well as of the morphological areas from irradiated hair (1-3). These studies showed that the physical and chemical modifications of hair resulted in characteristic patterns of damage correlating with the pigmentation of the hair and the individual ranges of sunlight. UV-A and the visible part of sunlight (VIS) damage hair significantly however, hair properties are also in- fluenced to a minor extent by UV-B and IR irradiation. Black hair is largely protected from the damaging effects of the irradiation by the pigment eumelanin. In contrast, blonde hair is detectably photochemically damaged due to low pigment content or pigmentation with pheomelanin. Some papers on the effect of sunlight on cosmetically pretreated hair, such as that which has been permanent waved, chemically bleached, or undergone oxidative dyeing, indi- cate a synergistic effect between pretreatment and irradiation (4,5). Thus, irradiation doses that do not cause visible modifications on natural black, blonde, or red hair lead to a clear photobleaching of dyed hair regardless of the hair color, mainly caused by the visible part of sunlight (5). According to Tatsuda et al. (4), chemically bleached hair is photochemically faded to a larger extent than natural black hair. In addition, UV and VIS rays reduce the wet 79

80 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS bundle tenacity of chemically bleached hair significantly in comparison to that of natural hair samples. The present paper will systematically check these initial findings on synergistic damage of human hair by cosmetic pretreatment and sunlight. Thus, brown human hair was cosmetically pretreated using permanent waving, chemical bleaching, or oxidative red dyeing, and subsequently irradiated with simulated sunlight. The latter was split in a special irradiation apparatus into UV-B, UV-A, VIS, and IR so as to determine the extent of modification of the respective ranges of wavelength (1). Color and tensile strength determinations as well as quantitative determination of internal lipids (IL) using cholesterol as an example allow us to make statements about photochemical modifications of the three main components of human hair: melanin, proteins, and lipids. The final discussion takes patterns of damage as a function of the irradiation range into consideration so as to be able to develop specific measurements for sun protection of cosmetically pretreated hair. MATERIALS AND METHODS HAIR SAMPLES Untreated brown hair was obtained from Herzig Co. as 25-cm-long tresses of European origin. COSMETIC TREATMENT OF HAIR Hair tresses were cosmetically pretreated using products from The Schwarzkopf Com- pany. For the permanent wave treatment, tresses were reduced by ammonium thiogly- colate (Style Wave X © from CLYNOL) and subsequently reoxidized for 10 min with 3 % H202 (Natural Styling Stabilifix©). Chemical bleaching was achieved using a 40-min treatment with one part Igora Brilliantblond © containing 55 % persulfates and two parts 6% H202 (Igora Oxigenta Lotion©). Another part of the hair sample was oxidatively dyed red for 30 min using p-toluylenediamine (one part Igora Royal Nuance R2 ©) and 6% H202 (one part Igora Oxigenta Lotion©). In order to obtain identical starting conditions for the hair surface, untreated, permed, bleached, and dyed hair tresses were immersed for 30 min in 1% citric acid, as this treatment is obligatorily used during bleaching. IRRADIATION OF HAIR The hair tresses were irradiated for a period of four weeks (672 h) in individual com- partments with UV-B, UV-A, visible light, IR, or global radiation at RH 70%. The description of the special constructed radiation chambers was given in the first part of these publications concerning the irradiation of hair (1). The applied wavelength ranges and intensities were: UV-B, 280-350 nm, 2.5 W/m2 UV-A, 320-400 nm, 48 W/m2 visible light, 370-780 nm, 463 W/m2 IR, 750-2800 nm, 440 W/m• global light, 280-1100 nm, 1037 W/m 2. In each case a tress of approximately 2.2 cm (1.5 g) of hair was used. The tress was turned over daily to assure uniform exposure to irradiation.