NUDE RAT SKIN PERMEABILITY 307 skin preparation immediately prior to use is eliminated. Skin variables, such as animal age and gender, are better controlled. Additionally, the use of frozen skin can be more economical than using freshly excised skin because of reduced housing and procurement COSTS. REFERENCES (i) (2) (3) (4) (5) (6) (7) (8) (9) (lO) (11) (12) R. J. Scheuplien and I. H. Blank, Permeability of the skin, Physiol. Rev., 59, 702-747 (1971). C. R. Behl, N. H. Bellantone, and G. L. Flynn, "Influence of Age on Percutaneous Absorption of Drug Substances," in Percutaneous Absorption, R. L. Bronauch and H. I. Maibach, Eds. (Marcel Dekker, Inc., New York, 1985), Ch. 14. B. Garcia, J. p. Marty, and J. Wepierre, Etude des facteurs conditionnant l'absorption percutanee des alcools incorpores dans des melanges eau-monooleate de sorbitanne polyoxyethylene-myristate d'iso- propyle, Int. J. Pharm., 4, 205-217 (1980). C. R. Behl and N. H. Bellantone, Influence of alkyl chain length on the in situ permeation of n-alkanols through fuzzy rat skins and comparisons with the in vitro data. Comparisons of the fuzzy rat and hairless mouse skin results, Presented at the 31 't Annual Meeting of the Academy of Pharmaceutical Sciences, Miami Beach, FL, 1983, Abstract #38. C. R. Behl, N. H. Bellantone, and J. Pei, Effects of alkyl chain length and anatomical site on the alkanol permeability through fuzzy rat skins, Presented at the I30 th Annum Meeting of the American Pharmaceutical Association, New Orleans, LA, 1983, Abstract #32. C. R. Behl, G. L. Flynn, and M. Barrett, Skin permeability profile of n-alkanols and water through Swiss (furry) mouse skin, In preparation. C. R. Behl, A. A. E1-Sayed, and G. L. Flynn, Influence of hydration on n-alkanol permeation through rat skin. Comparison with hairless and Swiss mice, J. Pharm. Sci. 72(1), 79-82 (1983). C. R. Behl and G. L. Flynn, Permeation profile of n-alkanols and water using Silastic © as a mem- brane, In preparation. C. R. Behl, R. Meyer, and G. L. Flynn, Percutaneous absorption by the living mouse--Uptake of water and n-alkanols across normal and stripped skin, Presented at the 128 th Annual Meeting of the American Pharmaceutical Association, St. Louis, MO, 1981, Abstract #22. C. R. Behl, N. H. Bellantone, J. Pei, A. W. Malick, and S. DelTerzo, Skin permeation studies of n-alkanols using fuzzy rat. In vitro/in situ correlations and comparisons with hairless mouse data, Submitted to Dr•g Dev. Ind. Pharm. (1986). S. M. Harrison, B. W. Barry, and P. H. Dugard, Effects of freezing on human skin permeability,J. Pharm. Pharmacol., 36, 261-262 (1985). J. Swarbrick, G. Lee, and J Brom, Drug permeation through the skin: I. Effect of storage condition of the skin, J. Invest. Derre. 78, 63-66 (1982).

j. Soc. Cosmet. Chem., 37, 309-327 (September/October 1986) Comparative study of skin care efficacy and in-use properties of soap and surfactant bars G. SAUERMANN, A. DOERSCHNER, U. HOPPE, and P. WITTERN, Beiersdorf AG, R and D Cosmed, Unnastr. 48, D-2000 Hamburg, West Germany. Received January 23, 1986. Synopsis The object of the investigation was to compare the irritancy and skin care efficacy of surfactant bars and soaps by classical provocative methods, viz., Finn chamber tests and by repeated regular use, to find reasons explaining the discrepancies between the corresponding test results and to present innovative methodolo- gies to study the efficacy of cosmetics. Three classical soaps and one surfactant bar were compared by Finn chamber test, measurement of pH values at the skin surface before and after removal of tape strips, measurement of cationic fluorescent dye sorption at the skin surface to evaluate quantitatively the amount ofanionic surfactants adsorbed at the skin surface and their penetration into deeper skin layers, measurement of skin surface roughness and transepi- dermal water loss, and determination of the potential to extract concerning ninhydrin-positive material from the horny layer. Considering the Finn chamber test, the irritancy of the classical soaps was higher than that of the surfactant bar. The pH value of the skin surface 24 hours after application of the soap solutions was --8. The pH value was detectable through the whole horny layer. The irritancy potential of the mixtures of free fatty acids precipitated by acidification of the conventional soaps was zero. The pH value within the horny layer after single use of conventional soap was shifted to significantly higher values within the upper cell layers removed by three tape strips. The density of anionic skin surface charge measured by adsorption of cationic dye was elevated after appli- cation of soaps or surfactant bars. It decreased rapidly after use of the conventional soaps and slowly after use of the surfactant bars. The differences caused by surfactant bar and conventional soap were seen to be significant after removal of skin by six tape strips. The surface roughness of skin, regularly treated with surfactant bar or one of the soaps, was not increased during the test period. The transepidermal water loss was increased significantly after treatment with the surfactant bar. The skin surface was depleted of pH-stabilizing substances by the conventional soap significantly less than by the surfactant bar. The main reason for the stronger irritation rate of classical soaps compared with surfactant bars using the Finn chamber technique seems to be the exhaustion of pH-buffering materials of the skin by the applied excess of soaps. Regular use did not confirm the above ranking. INTRODUCTION Patch tests are normally performed to evaluate the irritancy potential of externally ap- plied products. They use rather high concentrations of soap solutions (ca. 8%) and large 309