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J. Soc. Cosmet. Chem., 24, 385-393 (May 23, 1973) Studies on Potential Irritancy and Stinging KARL LADEN, Ph.D.* Presented April 12, 1972, Symposium on Skin-Environmental Responses and Protection, Society o1' Cosmetic Chemists o1' Great Britain Synopsis-ANIMAL and HUMAN METHODS for evaluating the STINGING POTEN- TIAL of materials placed on the skin have been devised. Using these tests, various ma- terials have been evaluated for stinging potential. In addition, the primary IRRITANCY of some of these compositions has been evaluated. The results indicate that stinging potential and primary irritancy are unrelated. It was also observed that no general con- clusions could be drawn as to predicting the stinging potential of solutions of acidic materials by considering solely the hydrogen ion concentration, tonicity, or the nature of the anion. INTRODUCTION Testing of cosmetic formulations for their skin irritancy potential has long been recognized as one of the safety measures required prior to marketing. To this end, a large number of both animal and human testing procedures have been described in the literature. A comprehensive reviexv of these methods has recently been published ( 1 ). In spite of extensive testing of this nature, it has sometimes been observed in our laboratory that prototype formulations which have low primary irritancy cause discomfort to the user in terms of low levels of stinging. Furthermore, it seemed that the stinging potential of a formula- tion was often totally unrelated to its primary irritancy. The purpose of this work was to develop some useful methods for measuring stinging potential of formulations and to gain some insight into relating chemical composition to stinging potential. This communication presents some of our preliminary find- ings in this area. *Gillette Research Institute, 1413 Research Blvd., Rockville, Md. 20850. 385