34 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS (2) R. Y. Lochhead, W. J. Hemker, J. Y. Castaneda, and D. Garlen, Cosmet. Toiletr., 101, 125 (1986). (3) S. E. Friberg, Micelies, microemulsions, liquid crystals, and the structure of stratum corneum lipids, J. Soc. Cosmet. Chem., 41, 155-171 (1990). (4) G. M. Eccleston, Multiple-phase oil-in-water emulsion, J. Soc. Cosmet. Chem., 41, 1-22 (1990). (5) H. Tsutsumi, R. Utsugi, and S. Hayashi, J. Soc. Cosmet. Chem., 30, 345 (1979). (6) S. E. Friberg, L. B. Goldsmith, I. Kayali, and H. Suhaimi, in Interfacial Phenomena in Biology, M. Bender, Ed. (Marcel Dekker, New York, in press). (7) S. E. Friberg and B. R. C. Langlois, Evaporation from emulsions, J. Dispers. Sci. Technol. (in press). (8) R. Y. Lochhead, The effect ofmesomorphic phase structure on the efficacy of skin moisturizing lotion, J. Soc. Cosmet. Chem. (in press). (9) S. E. Friberg and B. R. C. Langlois, A four-component phase diagram (in preparation). (10) W. D. Stein, in Transport and Diffusion Across Cell Membranes (Academic Press, New York, 1986). (11) P. C. Hiemenz, in Principles of Colloid Chemistry (Marcel Dekker, New York, 1981), pp. 381-382. (12) R. O. Potts and M. L. Francoeur, The influence of stratum corneum morphology on water perme- ability, Soc. Invest. Dermatol, 96, 495-499 (1991). (13) E. L. Cussler, S. E. Hughes, W. J. Ward III, and R. Aris, Barrier membrane, J. Membr. Sci., 38, 161-174 (1988). (14) S. E. Friberg and I. Kayali, Water evaporation from a model of stratum corneum, J. Pharmaceut. Sci., 78, 639-643 (1988).

j. Soc. Cosmet. Chem., 44, 35-52 (January/February 1993) Fluorescence-free UV/VIS reflection spectra of human skin G. SAUERMANN, A. HERPENS, D. DREWES, A. GRIMMERT, B. AUGUST, and U. HOPPE, Paul Gerson Unna Research Center of Beiersdorf AG, D-2000 Hamburg, and Fachhochschule fiir Chemieingenieurwesen, D-2000 Hamburg, Germany. Synopsis A fluorimeter operated in synchronous mode was used to record fluorescence-free UV/VIS reflection spectra of human skin. BaSO 4 or Teflon served as reflection standards. The variation coefficient of the spectral data showed a maximum around 350 nm. The relative remittance (normalized spectra) increased dramatically after cyanoacrylate stripping around 305 nm equivalent with loss of UV-absorption. Increase of moisture level by occlusion or washing of skin caused a similar but reversible change, washing with surfactants was provocing changes lasting for more than 24 hours. Exaggerated use of soap and surfactant bars drastically enlarged remittance around 300 nm. INTRODUCTION UV/VIS radiation impinging on the skin surface will be only partially directly reflected. About 5% of the total radiation energy is reflected from the surface (1). The remaining radiation entering the stratum corneum will be reflected, diffracted, and refracted, processes that are described in total as scattering (2). Therefore, the light beam will lose its original direction and tend to gain a more diffuse distribution within the skin. During its chaotic way through tissue, light will be diminished by endogenous and exogenous chromophores absorbing at different wavelengths: the longer the optical pathway, the more the loss by absorption. With increasing wavelengths, irradiation reaches deeper layers of the skin (3). A fraction of the incident radiation of different wavelengths, scattered from different penetration depths, will reach the skin surface again (= diffuse reflection). Depending upon the quality and quantity of the chromopheres that rays encounter on their penetration path, the recorded spectra will show more or less intense absorption peaks. The whole level and general shape of the spectra will be determined by the scattering properties of the skin getting increasingly turbid or less permeable with shorter wavelengths (1). To standardize spectra, the particular influences of lamps, optical geometry, and skin probes have to be eliminated. This is optimally achieved by producing relative spectra that show the diffuse remittance of skin in percentages of the reflectivity of a reflection standard like BaSO 4 or Teflon (reflection close to 100%, irrespective of wavelength). 35