METHOD FOR TRANSEPIDERMAL WATER LOSS 119 (20) (21) (22) (23) (24) (25) (26) (27) (28) (29) (30) (31) (32) (33) (34) (35) (36) (37) K. Grice and F. R. Bettley, The effect of skin temperature and vascular change on the rate of transepi- dermal water loss, Brit. J. Dermatol., 79, 582-588 (1967). K. Grice, Skin temperature and transepidermal water loss, J. Invest. Dermatol., 57(2), 108-110 (1971). T. Mathias, D. M. Wilson, and H. I. Maibach, Transepidermal water loss as a function of skin surface temperature, J. Invest. Dermatol., 77(2), 219-220 (1981). A. B. Goodman and A. V. Wolf, Insensible water loss from human skin as a function of ambient vapor concentration, J. Invest. Dermatol., 26(2), 203-207 (1969). D. Spruit and K. E. Malten, Humidity of the air and water vapour loss of the skin, Dermatologica, 138, 418-426 (1969). R. R. Bettley and K. Grice, The influence of ambient humidity on transepidermal water loss, Brit. J. Dermatol., 79, 575-581 (1967). K. Grice, H. Sattar, and H. Baker, The effect of ambient humidity on transepidermal water loss, J. Invest. Dermatol., 58(6), 343-346 (1972). Z. Felsher and S. Rothman, The insensible perspiration of the skin in hyperkeratotic conditions, J. Invest. Dermatol., 6, 271-278 (1945). P. Frost, Ichthyosiform dermatoses. III. Studies of transepidermal water loss, Arch. Dermatol., 98, 230-233 (1968). D. Dupuis, In vivo relationship between percutaneous absorption and transepidermal water loss ac- cording to anatomic site in man, J. Soc. Cosmet. Chem., 37, 351-357 (1986). M. M. Reiger and D. E. Deem, Skin moisturizers. II. The effects of cosmetic ingredients on human stratum corneum, J. Soc. Cosmet. Chem., 25, 253-262 (1974). G. E. Burch and T. Winsor, Diffusion of water through dead plantar, palmer and torsal human skin and through toe nails, Arch. Dermatol. and Syph., 53, 39-41 (1946). M. M. Reiger and D. E. Deem, Skin moisturizers. I. Methods for measuring water regain, mechan- ical properties, and transepidermal moisture loss of stratum corneum, J. Soc. Cosmet. Chem., 25, 239-252 (1974). I. H. Blank, The diffusion of water across the stratum corneum as a function of its water content, J. Invest. Dermatol., 82(2) 188-194 (1984). R. L. Bronaugh and R. F. Stewart, Methods for in vitro percutaneous absorption studies. IV: The flow-through diffusion cell, J. Pharm. $ci., 74, 64-66 (1985). J. R. Matias and N. Orentreich, The hamster ear sebaceous glands. I. Examination of the regional variation by stripped skin planimetry, J. Invest. Dermatol. 81(1), 43-46 (1983). M. E. Solomon, The use of cobalt salts as indicators of humidity and moisture, Ann. Appl. Bio., 32, 75-85 (1945). K. Sato and M. Nagai, Effect of emollients on transepidermal water loss of human skin, Cosmet. Toilet., 94, 39-41 (1979).

j. Soc. Cosmet. Chem., 39, 121-132 (1988) Improved optical discrimination of skin with polarized light j. PHILP, N. J. CARTER, and C. P. LENN, Environmental SaJ•ty Laboratory, Unilever Research, Colworth House, Sharnbook, Bedford MK44 1LQ, U.K. (J.P., N.J.C.), and Department of Fluid Engineering and Instrumentation, Cranfield Institute of Technology, Cranfield, Bedford MK43 OA, U.K. (C.P.L.). Received July 20, 1987. Synopsis A polarized illumination system is described that optically segregates the skin into two distinct regions, making the assessment of the clinical condition easier. It is possible to highlight, preferentially, the light reflected from the dermis with suppression of light reflected from the surface of the stratum comeurn and vice versa. Polarized reflection spectroscopy and polarized color photography are used to demonstrate the differences between reflected polarized light and light that is depolarized by multiple scattering in the skin. The former shows clear delineation of surface structure whilst the latter highlights the redness or erythemal condition of the skin. INTRODUCTION Visual assessment has always played an important part in evaluating the clinical condi- tion of skin. Trained personnel can estimate the erythemal levels, the degree of rough- ness and dryness, and any other changes that can be visually identified. The major problem with in vivo evaluations is the variety of scales used (1,2) and the discreteness presumed (3). There is also the added difficulty of interpreting the descriptions used semiquantitatively to define the clinical conditions (4-7). Seitz et al. (8) have at- tempted to overcome these uncertainties by proposing the use of macrophotography of hands showing semiquantitatively determined clinical conditions and to use these pho- tographs as reference standards. In this way, common reference standards would ensure long-term continuity of assessment. As early as 1941 Dent (9) recognised the enhanced detail that could be photographed when using monochromatic light of decreasing wavelength. More recently his approach has been extended by using ultraviolet light, with even more dramatic effect (10, 11). Any quantitative evaluation using this improved discrimination still requires subjective assessment. In the past three decades alternative approaches based on electronic instrumentation have been developed. These have been successful in quantitatively evaluating particular clinical conditions. Objective assessment of skin conditions using preferential interaction with light has been mainly based on reflection spectroscopic techniques. Using diffuse reflection spec- 121