26 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS the surface scale. In this domain, irreversible damage has occurred, especially at the edge of the endocuticular layer of the surface scale. We feel that this irreversible damage to the endocuticle during fiber extension due to grooming may well be responsible for the breaking off of scale fragments during wet combing that was observed by Swift and Brown (4). It is therefore an important part of the scale ablation process in which new surfaces are generated upon loss of the surface cuticle until the whole cuticular sheath has been abraded. During the extension of fine and coarse wool fibers, no scale lifting was observed. The response of the cuticular structure to the extension of wool fibers appears to be the relative sliding of the scales, with failure in the intercellular cement between cuticle cells. Scale lifting may be prevented by the higher rigidity of the scale cells of wool, which are thicker and more highly curved than those of human hair. ACKNOWLEDGMENTS The work reported here was carried out within the framework of the TRI Core Tech- nology Project, "Analysis and Quantification of Hair Damage," sponsored by companies in the international cosmetic industry. The authors would like to thank the sponsors for their financial support. The authors would further like to thank Dr. Yash Kamath, Director of Research at TRI, for many interesting discussions. REFERENCES (1) C. R. Robbins, "Chemical and Physical Behavior of Human Hair," 3rd ed. (Springer-Verlag, New York, 1994), pp 211-226. (2) S.C. Kelly and V. N. E. Robinson, J. $oc. Cosmet. Chem., 33, 203 (1982). (3) T. Kambe, 6th Int. Hair Science Syrup. DWI, Lueneburg, Germany, 1988. (4) J. A. Swift and A. C. Brown,.]. Soc. Cosmet. Chem., 23, 695 (1972). (5) V. N. E. Robinson, J. Soc. Cosmet. Chem., 27, 155 (1976). (6) L. Wolfram and L. Albrecht, J. $oc. Cosmet. Chem., 36, 87 (1985). (7) G. Laustriat and C. Hasselmann, Photochem. Photobid., 22, 295 (1975). (8) K. Schaefer,.]. Soc. Dyers Col., 107, 206 (1991). (9) J. A. Swift, Int. J. Cosmet. Sci., 13, 143 (1991). (10) C. R. Robbins and R. J. Crawford,.]. Soc. Cosmet. Chem., 42, 59 (1991). (11) W.J. Onions, Wool, an Introduction to its Properties, Varieties, Uses and Production (Interscience Publishers, New York, 1962), p. 13.

j. Soc. Cosmet. Chem., 47, 27-39 (January/February 1996) The effect of lipids, with and without humectant, on skin xerosis ROBERT S. SUMMERS, BEVERLY SUMMERS, PREM CHANDAR, CAROL FEINBERG, RICHARD GURSKY, and ANTHONY V. RAWLINGS, School of Pharmacy, Medical University of South Africa, P.O. Box 218, Medunsa 0204, South Africa (R. S. S., B. S. ), and Unilever Research US Inc., Edgewater, N.J. 07020 (P. C., C. F., R. G., A. V. R.). Received August 1995. Presented in part at the Society for Investigative Dermatology, April 1995 Synopsis Specialized lipids found in the stratum corneum, namely ceramides, have been shown to have beneficial skin properties due to their lipid bilayer-forming potential in the presence of cholesterol and fatty acids. We were interested in determining whether other bilayer-forming lipids, such as phospholipids, could deliver similar benefits and how these benefits compare with common moisturizer ingredients such as petrolatum and glycerol. We investigated a bilayer-forming mixture of phospholipids, cholesterol, and fatty acid for its effectiveness in treating soap-induced winter xerosis in double-blind, fully randomized clinical trials in which dryness on the dorsal aspect of the hands was visually assessed using a seven-point grading scale. Sixty-six healthy Caucasian women aged over 25 underwent a one-week soap "dry-down" and were treated for two weeks with twice-daily product applications in balanced treatment groups (N = 11). Treatments were compared statistically using repeated Wilcoxon rank sum tests (critical significance level of 5%). Examination of improvements in xerosis in vivo established that emulsions of phospholipids, cholesterol, and stearic acid alone, or thickened solutions of glycerol alone, did little to alleviate skin xerosis. When lipids and glycerol were combined, however, the emulsions acted in a synergistic way and reduced skin xerosis significantly and rapidly. In contrast, when phospholipids were replaced with petrolatum in the emulsions, the rate of xerosis alleviation was reduced, which implies that the bilayer-forming capabilities of phospho- lipids may be important in delivering optimal skin benefit. These studies demonstrate that lipids with bilayer-forming capabilities such as phospholipids can rapidly alleviate skin xerosis when combined with glycerol. INTRODUCTION Stratum corneum moisturization is essential for the normal functioning of the skin. The degree of moisturization depends directly on the inherent humetancy properties of the stratum corneum and on its water barrier function (for review, see reference 1). The structure of stratum corneum and its lipid content, probably both intercellular and covalently bound to corneocytes, affect barrier function (2-4). The lipids consist mainly of ceramides, cholesterol, and fatty acids the total and respective levels of these are 27