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j. Soc. Cosmet. Chem., 82, 171-177 (May/June 1987) Biophysical characterization of dry facial skin J. L. LEVEQUE, G. GROVE, J. de RIGAL, P. CORCUFF, A. M. KLIGMAN, AND D. SAINT LEGER, Laboratoires de Recherche de l'Oreal, 1 Avenue Eugene Schueller, 93600 Aulnay Sous Bois, France (J. L. L., J. d.R., P.C., D.S.L. ), Skin Study Center, 3401 Market Street, Philadelphia, PA 19104 (G.G.), and Department of Dermatology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 (A.M.K.). Received December 1 O, 1986. Synopsis Skin conductance, extensibility, corneocyte size, sebum excretion rate (SER), and transepidermal water loss (TEWL) were assessed for 5 5 healthy adults showing typical winter xerosis. The variation of these param- eters with the severity of skin dryness (assessed through a standardized clinical grading) was plotted. Both skin conductance and skin extensibility decreased with the severity of skin dryness, suggesting that winter xerosis may lead to either thicker or drier stratum corneum (SC). In addition, there is an inverse relation- ship between the size of corneocytes and the severity of the xerosis, which could mean that a subclinical inflammation process underlies this skin affliction. Results show no clear relationship between skin dryness and SER or TEWL. INTRODUCTION "No one can talk authoritatively about dry skin. Virtually everything that can be said is speculative and controversial" (1). While dry skin is a common disorder which can make people miserable, the fact is we know very little about it. Indeed, dryness is merely a descriptive term that implies lack of water, but this has not been shown conclusively. The ichthyotic syndromes can be considered as extreme examples of dry skin. Ironically, we know a good deal more about these rare conditions than the ordi- nary wintertime xerosis which is the focus of this work. Electron microscopy has so far not illuminated the basic structural defect that underlies dry skin. A currently popular approach to the enigmatic problem of dry skin is the use of a variety of ingenious instruments to measure the optical, mechanical, and electrical properties by noninvasive technology. Despite a rush of activity, the interpretation and relevance of the data obtained is still a matter of uncertainty and dispute. The various nonintrusive tech- niques that have been applied to this problem have been recently reviewed (2). The great appeal of this bioengineering approach is the securing of quantitative data ame- nable to statistical analysis. Another valuable feature is that the various tests can be speedily performed, enabling measurements on large sample sizes, a partial antidote to the marked individual differences which plague studies of human skin. Some of these are of interest as they are usually simple, noninvasive, and can therefore be applied on 171