MOISTURIZING FUNCTION OF LANOLIN 193 •L. L•x?B • Figure 14. Lanolin/marker concentrated at long area of cell contact. A feature of Figure 14 is a long line of contact between two corneocytes where lanolin or marker (arrows) has concentrated, presumably in the lipid layer on the surface of corneocytes. Evidence of this was seen earlier in Figures 2 and 12. Figure 15 is also interesting, showing distinctly a number of short trilaminar structures, with a spacing of 25 to 50 nm, which have taken up a high concentration of lanolin or lead salt. These apparently lie within corneocytes about three layers down from the surface of the skin. This spacing seems too great for intercellular lipid/water bilayers, but it is closer to that of cell envelope material, although how fragments of envelope could penetrate to the interior of the corneocytes is not clear. It may perhaps be evidence of a lipid layer surrounding a short protein fibril. CONCLUSIONS Evidence has been found that is in agreement with the postulated mechanisms by which lanolin could act as an emollient and moisturizer: 1. Lanolin applied to the stratum corneum penetrates throughout its full depth, down to the stratum granulosum. 2. Lanolin located in intercellular spaces appears to form spontaneously a w/o emulsion with some of the epidermal water. 3. Lanolin (or lead marker) can penetrate to the interior of corneocytes. 4. Lanolin and/or lead marker appears to have the power to become incorporated in the

194 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 15. Small, apparently intracellular, laminar structures that contain lanolin/marker in their outer layers. intercellular lipid bilayers, at least (apparently) in trilaminar structures forming the outer envelope of corneocytes. This work suggests that lanolin achieves its moisturizing action by absorption deep into the stratum corneum. Once there, whether its action is partial occlusion of natural water pathways, or due to being taken up into natural lipid bilayers, or due to providing an additional water reservoir, is not yet entirely clear. There is, however, some evidence suggesting that lanolin may penetrate corneocytes and become incorporated into laminar structures such as cell envelope material. Evidence suggesting the spontaneous emulsi- fication of epidermal water by intercellular lanolin has been seen. ACKNOWLEDGMENT The assistance of Dr. Ashley J. Wilson of CCTR, University of York, Heslington, England, in interpreting the photomicrographs is gratefully acknowledged. REFERENCES (1) E. W. Clark, A brief history of lanolin, Pharm. Historian, 10, 5-6 (1980). (2) E. W. Clark, New concepts of lanolin. Presentation at In-Cosmetics Seminar, NEC, Birmingham, England, March, 1990. (3) D. H. Powers and C. Fox, A study of the effect of cosmetic ingredients, creams and lotions on the rate of moisture loss from the skin, Proc. $ci. Sec. Toilet Goods Assoc., 28, 21-26 (1957).