INTER-SPECIES VARIATION IN DERMAL REACTIVITY 381 glycol in solution, and I think that you might compare the sodium lauryl sulphate with soap solutions, which would probably cause similar swelling of the skin. MR. DAVIES: We apologize for any aspersions cast against propylene glycol in this study we were concerned more with the differences in response to a given chemical, rather than comparisons of the chemicals themselves. If we had used 30•o propylene glycol we would most probably have seen no response in any of the species--and this would have contributed little to our study. The 100•o propylene glycol, however, did indicate some species difference in sensitivity. We do have a tentative research programme which may clarify your criticisms. We wish (a) to extend the range of chemical irritants examined (b) to apply a given irritant in a number of vehicles and (c) to apply varying concentrations of the irritant in a given vehicle. The results of these studies may provide some further clarification of the problems of predictive patch testing.

J. Soc. Cosmet. Chem. 23 383-391 (1972) ¸ 1972 Society of Cosmetic Chemists of Great Britain The importance of the vehicle in formulating sunscreen and tanning preparations E. R. KRAFT,* S. G. HOCH*, R. A. QUISNO* AND E. A. NEWCOMB* Presented on 6th October 1970 in London at the Symposium on 'New developments in lanolin and its derivatives', organized by the Society of Cosmetic Chemists and the Society of Cosmetic Chemists of Great Britain. Synopsis--This study was undertaken to determine the functional significance of the VEHICLE in SUNTAN PREPARATIONS. Three o/w vehicles, three oil-based vehicles and two controls were tested on HUMAN subjects under both natural SUNLIGHT and ARTIFICIAL LIGHT (a xenon-mercury lamp developed by one of the authors). The same screening agent was used in each vehicle. In general, the oil-based vehicles gave superior protection against sunburn. The o/w EMULSIONS were superior in promoting tanning although one oil-based vehicle gave good results in protection against burn and in promoting tanning. Previous work in the field of sunscreen studies has placed a great deal of emphasis on the importance of the sunscreen used, and correlations have been made between the efficacy of a sunscreen and the protection given by a finished product (1). In addition to the active sunscreen ingredient, the vehicle may play a far more important role than formerly thought. We believe the following factors should be considered: (1) The concentration of sunscreen in the original product versus con- centration on the skin after water evaporation. (2) The emulsion remaining on the skin after water evaporation, and the washability and the susceptibility to re-emulsification when exposed to perspiration and bathing. * Maimstrom Chemical Corporation, Linden, N.J. 07036, U.S.A. ? Hill Top Research Inc, Miamiville, Ohio, U.S.A. 383