288 JOURNAL OF COSMETIC SCIENCE containing the repellent methyl neodecanamide against Blattella germanica (L.), Intl. Pest Control, 38, 88-91 (1996). (8) C. F. Curtis, J. D. Lines, J. Ijumba, A. Callaghan, N. Hill, and M. A. Karimzad, The relative efficacy of repellents against mosquito vectors of disease, Med. Vet. Entomol., 1, 109-119 (1987). (9) M. Bates, The Natural History of Mosquitoes (Macmillan, New York, 1949), pp. 17-22. (10) W. K. Reisen and M. Aslamkhan, Biting rhythms of some Pakistan mosquitoes (Diptera:Culicidae), Bull. Entomol. Res., 68, 313-330 (1978). (11) W. S. Abbott, A method of computing the effectiveness of an insecticide,J. Am. Mosq. Control Assoc., 3, 302-303 (1987). (12) H, I. Maibach, A.A. Kan, and W. Akers, Use of insect repellents for maximum efficacy, Arch. Dermatol., 109, 32-35 (1974).

j. Cosmet. Sci., 54, 289-300 (May/June 2003) Effect of soaking and natural moisturizing factor on stratum corneum water-handling properties MARTY O. VISSCHER, GAURAV T. TOLIA, R. RANDALL WICKETT, and STEVEN B. HOATH, The Skin Sciences Institute (M. O.V., S.B.H.), Cincinnati Children's Hospital Medical Center (M.O.V., S.B.H.), and College of Pharmacy (G.T.T., R.R.W.), University of Cincinnati, Cincinnati, OH 45267. Accepted for publication June 18, 2002. Presented as a poster at the Annual Scientific Seminar of the Society of Cosmetic Chemists, New Orleans, May 2001. Synopsis Stratum corneum (SC) hydration is partially regulated by water-soluble molecules, natural moisturizing factor (NMF) that is associated with the corneocytes. Routine water exposure, e.g., bathing, may deplete NMF and alter the SC water-handling properties. We determined the effects of bathing and solvent extraction on the volar forearm skin of eleven healthy volunteers. Acetone/ether (A/E) was used to remove surface and upper SC lipids. Adjacent sites were soaked for ten minutes or treated with the A/E-plus-soak combination. Subsequently, an NMF formulation was applied to the treated sites, and transepidermal water loss (TEWL), hydration, and moisture accumulation rate (MAT) were measured. A/E extraction increased TEWL, but did not effect MAT. Soaking produced a short-term increase in TEWL, followed by a decrease, and substantially reduced MAT, an effect that was maintained for five hours. NMF application significantly decreased TEWL and significantly increased MAT for all sites. The replacement experiment suggests that the MAT reduction occurred as a result of extraction of hygroscopic NMF components. The effects of soaking and NMF application are more readily detected by the MAT technique, whereas TEWL is more sensitive to A/E extraction. The results support the use of multiple assessments of barrier function and raise questions about the effects of cumulative repeated water exposure on SC function. INTRODUCTION The stratum corneum (SC) forms a dynamic interface between the environment and the internal milieu. Proper hydration of the SC is essential to provide an effective barrier to water loss and for optimum skin function (1). Plasticization of the SC imparts flexibility and prevents cracking, fissuring, barrier damage, and loss of integrity. SC moisturization occurs as a result of the inherent barrier to water loss provided by the corneocytes embedded in the lipid bilayer matrix and by the inherent humectancy of specific cellular components (2). Hydration is necessary for proper desquamation of the outer SC by facilitating degradation of desmosomal attachments (3). Topical moisturizers, used to treat dry, scaly skin conditions, provide humectancy and water-holding capability with 289