J. Soc. Cosmet. Chem. 24 245-258 (1973) (•) 1973 Society of Cosmetic Chemists of (7reat Britaln A critical evaluation of the methods available for measurement of antiperspirancy T. A. BAKIEWICZ* Presented on the 12th April 1972 in Oxford, at the Symposium on 'Skin--Environmental responses and protection', organized by the Society of Cosmetic Chemists of Great Britain. Synopsis---The different METHODS for the evaluation of ANTIPERSPIRANTS are reviewed. The difficulties in INTERPRETATION of the results obtained using these different METHODS are discussed. INTRODUCTION The expansion in sales of antiperspirants (1, 2) in recent years has resulted in the appearance on the market of many new products. The evaluation involved in the development of these products, as well as the research towards new actives, has resulted in a renewed interest in the methods for the evaluation of antiperspirants. The purpose of this com- munication is to discuss, critically, the methods available to the cosmetic scientist for the evaluation associated with the development of new products, and methods for providing technical support for marketed form.ulae. ECCRINE SWEATING The sweat glands can be divided into two types, eccrine and apocrine. The apocrine glands, in man, have a limited distribution on the body *Unilever Research, Laboratory, 455 London Road, Isleworth, Middlesex. 245

246 ]'OURNAL OF THE SOCIETY OF COSMETIC CHEMISTS surface, and their oily secretions, although relatively sparse, are thought to be a contributing factor in the formation of body odour (3). The eccrine glands are distributed over the whole body surface (4), they secrete a pro- fuse watery liquid which is responsible for the unsightly wet patches under the arms, which appear during hot weather or during moments of stress. Most people, when they are in conditions of moderate temperature and little or no anxiety produce very little sweat. For the purpose of the anti- perspirant tests, therefore, it is necessary to induce sweating artificially, so as to try and reproduce the sort of perspiration rates against which the products are likely to be used. This can be done in several ways, by emo- tional stimulation of the subject (5), by heat stimulation (6), or a combina- tion of the two such as encountered during strenuous exercise or even by pharmacological means (7). THE PURPOSE OF AN ANTIPERSPIRANT The aim of an antiperspirant product should be to keep sweating below the critical level where people are conscious of the problem and not neces- sarily totally to inhibit sweating. Since little is known about this critical level it is normal to measure either the reduction in sweating in absolute terms, as a percentage of the untreated response or to compare the effective- ness of two products directly, i.e. is product A better or worse than product B at redudng perspiration? The ultimate test of any antiperspirant must be the willingness of the consumer to buy the product and probably involves the user's subjective judgement about how effective the product is at stopping or reducing axillary wetness. Information on consumer preference is difficult to obtain and from overall preferences it is impossible to separate the individual product attributes into discrete units. The preference may be due to halo effects from perfume, effectiveness against body odour or non-functional attributes which tend to confuse the antiperspirancy evaluation. It is there- fore very important to the scientist that he should be able to isolate such a measurable attribute as antiperspirancy, quickly, efficiently and accurately. This communication shows how this can be done in the laboratory and how to avoid some of the misleading information that can come out of these tests.