384 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS massaged in the same way, did not show this thickening. The response of the skin was due directly to the application of the extract, and not due to any mechanical irritation.

J. Soc. Cosmetic Chemists 15 385-394 (1964) ¸ 1964 society of Cosmeti• Ckemists of Great Britai• TESTING DRUGS FOR DERMAL TOXICITY G. F. SOMERS, D.Sc., Ph.D., F.P.S.* Presented at the Symposium on "Toxicology of Cosmetic Materials", at Leamington, Warwicks., on 20th November 1963. Methods for determining local toxicity on the skin and mucous mem- branes, and for assessing systemic dermal toxicity (acute and chronic), are descri•. Chemical substances in contact with the skin may have toxic effects. These can occur locally, the compound causing irritation and damage to the skin or the compound may be absorbed into the general circulation, leading to systemic toxic effects. In addition, particularly in humans, the skin may become sensitized showing allergic reactions upon repeated exposure. As in all toxicological work, initial studies of derreal toxicity should be carried out in animals. The results obtained must be interpreted with caution, and can only be a guide to the possible dangers in man. There are considerable structural and physiological differences between animal and human skin. Tests on animal skin will detect really toxic and irritant substances, and therefore provide a valuable first line of defence. Results obtained with minor irritants tend to be misleading, and sensitization studies can only really be made on human skin. Finally, it should be recognized that medicinal substances are often applied to damaged and diseased skin where the absorption characteristics may be completely changed. LOCAL TOXICITY Skin A primary irritation of the skin occurs when a compound first comes into contact with it. In animals it is usually determined on the skin of the rabbit or guineapig. It has been suggested that the pig should be the animal of choice, because its skin is most similar to human skin, but they are difficult animals to handle. Most workers use a method similar to that described by Draize (1). Lilly Research Laboratories Ltd., Liverpool 24, Lancs. Now at Reckitt & Sons, Ltd., Hull, Yorks. 38,5