THE CHLORINE-HAIR INTERACTION 105 (2) J. Lindberg and N. Gralen, Measurement of friction between single fibers. II. Frictional properties of wool fibers measured by the fiber-twist method, Text. Res. J., 18, 287-301 (1948). (3) G.J. Schuringa, T. Konings, and A. J. Ultee, Jr., Osmotic active substances of the Allw/3rden reaction, Text. Res. J., 23, 645-646 (1953). (4) J. H. Bradbury and J. D. Leeder, Keratin fibers. IV. Mechanism of the Allw/3rden reaction, Aust. J. Biol. Sci., 25, 133-138 (1972). (5) R. Beyak, C. F. Meyer, and G. S. Kass, Elasticity and tensile properties of human hair. I. Single fiber test method, J. Soc. Cosmet. Chem., 20, 615-626 (1969).

j. Soc. Cosmet. Chem., 39, 107-119 (March/April 1988) A new in vitro method for transepidermal water loss: A possible method for moisturizer evaluation L. M. LIEB, R. A. NASH, J. R. MATIAS, and N. ORENTREICH, St. John's University, Jamaica, NY 11439 (L.M.L., R.A.N.) and Orentreich Foundation for the Advancement of Science, Inc., 910 Fifth Ave., New York, NY 10021 (J.R.M., N.O.) Received October 19, 1987 Synopsis Transepidermal water loss (TEWL) through the ventral skin of the hamster ear was determined using a modified flow-through diffusion apparatus. Tritium-labeled water was allowed to permeate through the dermal/epidermal layers. Water vapor was collected in a closed system by adsorption onto solid anhydrous calcium chloride in a separately attached receiver. The desiccant was removed, dissolved in water, and the radioactivity determined by liquid scintillation counting. The rate of TEWL was determined for various durations of exposure to the desiccated environment, in the temperature range between 5 and 40øC. TEWL rate reached a maximum one hour after exposure, and then decreased to a steady state with time. TEWL increased exponentially with increasing temperature in accordance with the Arrhenius relationship. An activation energy value of 13 Kcal/mole was obtained. At incubator temperature of 22øC, the rate of TEWL was found to be 152 _+ 14 p,g/cm2/hr, which agrees with previously reported values obtained by in vivo methods of testing. The present technique is proposed as a rapid in vitro method for measuring TEWL and as a possible pretest for assessing efficacy of potential skin-moisturizing agents. Four agents were studied for their effect on water permeability. The agents tested were mineral oil, castor oil, sesame oil, and 25% glycerin in water. Skin membranes treated with occlusive agents such as mineral oil, castor oil, and sesame oil showed a marked decrease in the TEWL rate, while those membranes treated with the humectant, 25% glycerin in water, showed a marked increase in the TEWL rate. Similar results using these same agents have been reported previously. INTRODUCTION Blank showed that proper hydration of the stratum corneum is a primary factor in maintaining skin softness and flexibility (1,2). Other constituents of skin, such as pro- teins and lipids, play a minor role by influencing the water-binding capacity of the stratum corneum. Appearance and barrier function of the skin is affected, if it is not optimally hydrated (3). This effect is exhibited in low relative humidity environments, where the skin becomes dry, flaky, and/or chapped. When skin hydration increases at higher relative humidity, the water content and the permeability of skin increases (1,2,4-10). It is considered supple, flexible, pliable, and less likely to chap, fissure, and crack (1,2, 11- 14). Some cosmetic chemists regard moisturization as any means to increase water content and maintain this level over a period of time (15). "A moisturizer," as defined by Kligman (16) "is a topically applied substance or product that overcomes the signs and 107