IRON CONTENT OF EPIDERMIS 217 or immunohistochemistry as localized deposits. That work did not reveal any deposits in the epidermis. The methods used, though, were not particularly sensitive to low levels of iron, which would occur if there were a more uniform distribution throughout that tissue compartment. The present work, while based on analysis of relatively few skin samples, indicates epidermal iron levels similar to those we observed previously for whole skin (primarily dermis). Our values are also similar to those reported by others (13,14) for human epidermis (26 and 98 ppm, respectively) of undefined solar exposure history. Epidermal iron is probably more uniformly distributed than in dermis, thus requiring the use of sensitive atomic absorption to detect it. This iron could participate in epidermal photodamaging events, such as skin cancer. While the basal level of iron in non-exposed epidermis is potentially available as a catalyst, the greater level in exposed skin provides an increased potential for formation of reactive oxygen. ACKNOWLEDGMENT We gratefully acknowledge Dr. David L. Windsor of the Procter & Gamble Company for his iron analytical work. REFERENCES (1) (2) (3) (4) (5) (6) (7) (8) (9) (lO) (11) (12) (13) (14) D. L. Bissett, R. Chatterjee, and D. P. Hannon, Chronic ultraviolet radiation-induced increase in skin iron and the photoprotective effect of topically applied iron chelators, Photochem. Photobid., 54, 215-223 (1991). S. S. Ranade, P. Murugaiyan, B. S. Manerikar, and S. D. Joshi, Alteration of macromolecular events and elemental levels in the skin of UVC exposed hairless mice, Physiol. Chem. Phys. Med. NMR, 18, 197-205 (1986). G. R. Buettner, Activation of oxygen by metal complexes and its relevance to autoxidative processes in living systems, Bioelectrochem. Bioenerg., 18, 29-36 (1987). • H. B. Dunford, Free radicals in iron-containing systems, Free Rad. Biol. Med., 3, 405-421 (1987). A. Puppo and B. Halliwell, Formation of hydroxyl radicals from hydrogen peroxide in the presence of iron, Biochem. J., 249, 185-190 (1988). G. Minotti and S. D. Aust, The role of iron in initiation of lipid peroxidation, Chem. Phys, Lipids, 44, 191-208 (1987). J. M. Braughler, L. A. Duncan, and R. L. Chase, The involvement of iron in lipid peroxidation, importance of ferric to ferrous ratios in initiation, J. Biol. Chem., 261, 10282-10289 (1986). K. J. A. Davies, Protein damage and degradation by oxygen radicals. I. General aspects, J. Biol. Chem., 262, 9895-9901 (1987). S. Inoue and S. Kawanashi, Hydroxyl radical production and human DNA damage induced by ferric nitrilotriacetate and hydrogen peroxide, Cancer Res., 47, 6522-6527 (1987). M. J. Peak and J. G. Peak, Hydroxyl radical quenching agents protect against DNA breakage caused by both 365-nm UVA and by gamma radiation, Photochem, Photobid., 51, 649-652 (1990). H. C. Schroder, R. Messer, M. Bachmann, A. Bernd, and W. E. G. Muller, Superoxide radical- induced loss of nuclear restriction of immature mRNA: A possible cause for aging, Mech. Age Der., 41, 251-266 (1987). B. F. Van Duzee, Thermal analysis of human stratum corneum, J. Invest. Dermatol., 65, 404-408 (1975). L. Molin and P.O. Wester, Iron content in normal and psoriatic epidermis, Acta Dermatol., 53, 473-476 (1973). K. Kurz, G. K. Steigleder, W. Bischof, and B. Gonsior, PIXE analysis in different stages ofpsoriatic skin, J. Invest. Dermatol., 88, 223-226 (1987).

J. Soc. Cosmet. them., 43, 219-227 (July/August 1992) Short-term penetration of lanolin into human stratum corneum E. W. CLARK, Westbrook Lanolin Company, Laisterdyke, Bradford, West Yorkshire, England, BD4 8A U. Received January 23, 1992. Synopsis Lanolin is readily absorbed by the human skin, and since it contains both free and esterified cholesterol and fatty acid esters, it has at least in part some similarities to the intercellular lipids in stratum corneum. It is widely used as an effective emollient. As the first stage of a wider investigation into the mode of action of lanolin on the skin, the present study examines the extent of penetration of lanolin into the stratum corneum without attempting to find, at this stage, whether the substance is located intercellularly, in hair follicles, in sweat ducts, or elsewhere. It is already known not to lie merely in surface irregularities. Anhydrous lanolin was applied at a loading of 2 mg cm- 2 to an area of 2 x 1 cm of the flexor aspect of the inner forearm (in vivo). The treated area of stratum corneum was then removed in layers by 30 successive tape strippings, and lanolin contents of the strippings were determined quantitatively by a spectrophotometric method based on the Liebermann-Burchardt reaction for steroids, developed to give a limit of determination in the region of 50 }xg of lanolin and a sensitivity of 1.25 mg lanolin per unit absorbance on the linear portion of the calibration graph. The method is described in detail. Total recovery of lanolin was between 98.8 and 103.1% of that applied, the major portion being found in the first 12 strippings but traces still being detectable in the deepest layers adjacent to the stratum lucidum. The profile of lanolin content in the stratum corneum, when graphed, gave a curve very similar to another one previously obtained in a pilot study, and also similar to a curve published by other workers which related corneocyte removal by tape stripping to a depth within the stratum corneum. There appeared to be no significant transport of lanolin through the stratum corneum into underlying layers. Interference in the spectrophotometric method by the adhesive tape and other materials used was taken into account. The extent of interference by natural steroids in the stratum corneum was quantified by separate experiments and was found to be variable but very small. INTRODUCTION Intercellular lipids have been shown to influence the moisture-retaining capacity of human stratum corneum (1,2), and a bilayer arrangement of polar compounds such as cholesterol, glycerides, fatty acids, ceramides, and phospholipids has been demon- strated. A review was given by Ward and du Reau (3). Lanolin (the term implies the 219