pH AND IRRITANCY 245 SUMMARY The above studies give a consistent picture of the contribution of pH to the mildness and harshness of the soap/detergent and soap-based compositions described. It can be con- cluded that the lower irritation potential of bar A compared to bar B is directly related to the difference in alkalinity as measured by pH. The pH, therefore, has a significant effect on the irritation potential of soap-based cleansers. This is consistent with infor- mation appearing in the recent patent literature and is in accord with the intrinsic chemistry of these ingredients (29). Alkaline soap-based cleansers are harsher to the skin than soap-based compositions that are formulated to a neutral pH. ACKNOWLEDGMENTS The authors wish to thank G. Nicoll, M. F. Petko, M. MoreIll, T. Farrell, J. Wong, D. Borowski, and A. P. Greene for their technical assistance and contributions to this article. REFERENCES (1) (2) (3) (4) (5) (6) (7) (8) (9) (lo) (11) (12) (13) (14) (15) (16) R. I. Murahata, R. Touton-Quinn, and M. B. Finkey, Effect of pH on the production of irritation in a chamber irritation test, J. Am. Acad. Dermatol., 18, 62-66 (1988). D. Spruit, Evaluation of skin function by the alkali application techniques, Curr. Probl. Dermatol., 3, 148-263 (1970). K. Bucher, K. E. Bucher, and D. Walz, Irritant actions of unphysiological pH values. A controlled procedure to test for topical irritancy, Agents and Actions, 9, 124-132 (1979). R. Bechor, A. Zlotogorski, and S. Dikstein, Effect of soaps and detergents on the pH and casual lipid levels of the skin surface, J. Appl. Cosmetol., 6, 123-128 (1988). G. Sauermann, A. Doerschner, U. Hoppe, and P. Wittern, Comparative study of skin care efficacy and in-use properties of soap and surfactant bars,J. Soc. Cosmet. Chem., 37, 309-327 (1986). H. C. Korting, M. Kober, M. Mueller, and O. Braun-Falco, Influence of repeated washings with soap and synthetic detergents on pH and resident flora of forehead and forearm, Acta Derm. Venereol. (Stockh.), 67, 41-47, (1987). H. C. Korting, M. Megele, S.C. C. Mehringer, et al., Influence of skin cleansing preparation acidity on skin surface properties. Int. J. Cosmet. Science, 13, 91-102 (1991). M. Rieger, The apparent pH on the skin, Cosmet. Toiletr., 104, 53-60 (1989). P. J. Frosch, "Irritancy of Soap and Detergent Bars," in Principles of Cosmetics for the Dermatologist, P. Frost, Ed. (Mosby, St. Louis, 1982), pp. 5-12. W. G. Van Ketel, D. P. Bruynzeel, P. D. Bezemer, and H. I. Stamhuis, Toxicity of handcleaners, Dermatologica, 168, 94-99 (1984). P. G. M. van der Valk, M. C. Crijns, J. P. Nater, and E. Bleumink, Skin irritancy of commercially available soap and detergent bars as measured by water vapour loss, Dermatosen, 37, 87-90 (1984). B. Komp, Skin compatibility tests--Importance in skin cleansing product development, Cosmet. Toiletr., 102, 89-95 (1987). J. H. Hassing, J. P. Nater, and E. Bleumink, Irritancy of low concentrations of soap and synthetic detergents as measured by skin water loss, Dermatologica, 164, 314-321, (1982). M. O. Visscher, S. E. Michaels, and B. H. Keswick, A clinical test method for assessing the irritation potential of skin cleansing products. Presented at the 48th Annual Meeting of the American Academy of Dermatology, 1989. W. Gehring, M. Gehse, V. Zimmerman, and M. Gloor, Effects of pH in a specific detergent multicomponent emulsion on the water content of stratum corneum, J. Soc. Cosmet. Chem., 42, 327-333 (1991). J. L. Antoine, J. L. Contrerras, and D. J. Van Neste, pH influence of surfactant-induced skin irritation, Dermatosen, 37, 96-100 (1989).

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