PROBLEMS OF PREDICTIVE TESTING 359 (15) I,anman, B. M., et al., The role of human patch testing in a product development pro- gram, Proc. Joint Conf. Cosmet. Sci., Washington, D. G., 135-45 (1968). (16) Kligmarl, A.M., and Wooding, W. M., A method for the measurement and evaluation of irritants on human skin, J. Invest. Derrnatol., 49• 78-94 (1967). (17) Wolcott, G. L., A plea for in-use testing of cosmetics, Drug Cosmet. Ind., 93, 155-265 (1963). (18) Rieger, M. M., and Battista, G. W., Some experiments in the sa[ety testing o• cosmetics, J. Soc. Cosmet. Chem., 15• 161-72 (1964). (19) Kligman, A.M., Evaluation of cosmetics for irritancy, Toxicol. Appl. Pharmacol., Suppl. 3, 30-44 (1969). (20) Justice, J. D., et al., The correlation between animal and human tests in assessing product mildness, Proc. Sci. Sect. Toilet Goods ASS., •5• ]2 (1961). (21) Kligman, A.M., The identification of contact allergens by human assay. II. Factors influencing the induction and measurement of allergic contact dermatitis, J. Invest. Dermatol., 47• 375-92 (1966). (22) Forsbcck, M., et al., The [requency of allergic diseases among relatives to patients with allergic eczematous contact dermatitis, Acta Dermato-Venereol., 46• 149-52 (1966). (23) Baer, R. L., et al., Changing patterns of sensitivity to common contact allergens, Arch. Dermatol., 89, 3-8 (1964). (24) Agrup, G., Sensitization induced by patch testing, Brit. J. Dermatol., 80, 631-4 (1968). (25) Magnusson, B., and Hersle, K., Patch test methods. II. Regional variations of patch test responses, Acta Dermato-Venereol., 45, 257-61 (1965). (26) Magnusson, B., and Hersle, K., Patch test methods. III. Influence of adhesive tape on test response, Ibid., 46, 275-8 (1966). (27) Lowhey, E. D., Attenuation of contact sensitization in man, J. Invest. Dermatol., 50, 244-9 (1968). (28) Rebelh), D. J. A., and Suskind, R. R., The effect of common contactants on cutaneous re- activity to sensitizers, Ibid., 41, 67-80 (1963). (29) Sipos, K., Chemical hypersensitivity and dermatological diseases, Dermatologica, 135, 421-32 (1967). (30) Hjorth, N., Seasonal variations in contact dermatitis, Acta Dermato-Venereol., 47• 409-18 (1967). (31) BeltIcy, F. R., and Grice, K. A., The effect of sweating on patch test reactions to soap, Brit..J. Dermatol., 78, 636-9 (1966).

.l. Soc. Co.•met. ( hem. 22, 361-368 (May 27, 1971) Measurement in Vivo of Transepidermal Moisture Loss GENE R. BERIJBE, B.S., MONROE MESSINGER, B.S., and MURRAY BERDICK, Ph.D."* Presented May 26, 1970, New York City Synopsis--A technique is describcd for evaluating the effect of a cosmetic product on the rate of TRANSEPIDERMAL MOISTURE LOSS in human subjects. The thickness of product necessary to reduce the rate to zero is calculated and defined as the OCCLUSIVE THICK- NESS, a significant and inherent property of the product, independent of human subject variation. ]NTRODUCTION I,oss of water from the skin is an important physiological function. Blank (1) has stated that the water content of the stratum comeurn is probably the prime factor in determining its softness and flexibility, mak- ing the measurement of the effect of a cosmetic product on the moisture loss rate important to the cosmetic chemist. A large number of methods has been developed to measure the mois- ture loss in vivo. Noninstrumental methods such as the desiccator method of Powers and Fox (2) and the cold trapping of vapor from a stream of gas passing over the surface of the skin have been used with a limited degree of success. Thiele and Schutter (3) have described an in- strumental approach utilizing a salt crystal method. Later, these same authors presented a critical review concerning an improved salt crystal method and electrolytic methods (4). Electrolytic methods were also * Chesebrough-Pond's Inc., Research & Control Laboratories, Clinton, Conn. 06413. 361