Book review PATCH TESTING GUIDELINES K. E. Malten, Catholic University of Nijmegen J.P. Nater, State University of Groningen W. G. van Ketel, Free University of Amsterdam. (1976) Dekker and van de Vegt, Nijmegen, the Netherlands. Paperback Dfl 29.5. This is an exceedingly practical paper- back written by a group of authors who probably have as much experience as anyone in the field. They provide a broad selection of hints and tips, mainly of empirical origin rather than academic. Obviously this is indispens- able for those called upon to carry out patch-testing of the type discussed but the precise aims of the testing are important when considering its rele- vance for those without a direct interest in the management of skin patients. Professor Malten and his co- authors deal with the technique of patch-testing essentially for diagnostic purposes. Cosmetic scientists are more often concerned with predictive (so- called 'prophetic') testing and the differences are perhaps worth re- iterating. Patch-testing may be used to study both irritation and allergic skin response or sensitization, but in the present context, we are only concerned with the latter. A dermatologist is usually seeking to determine the cause 329 of allergic contact dermatitis in a particular patient. By contrast, the cosmetic scientist wants to know whether a raw material or a formula- tion has an abnormally high propen- sity to elicit sensitization responses in a large population of users. One of the striking differences between these approaches mentioned in the book, is seldom appreciated except by dermatologists. This in- teresting fact is that an individual may become sensitized to a particular com- pound without showing any clinical signs of qualitatively or quantitatively altered skin condition, i.e. without developing an allergic contact derma- titis. Indeed a patient with a skin con- dition elicited by one compound may also be capable of giving positive patch-test responses to several others, although exposure to these has not so far resulted in manifest skin problems. So, in treating the individual patient, the physician is primarily concerned to find the particular substance(s) to which his skin is actually responding on the other hand, the cosmetic re- search worker wants to know the overall sensitizing capacity of his test material, whether or not in particular individuals any skin disorder is pro- voked. Hence approaches suitable for clinical practice and cosmetic re- search are related but not the same.

330 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS An illustration of the practical merit of the book is shown in the advice to use square patches, since irritant responses are usually confined to the original shape (and size) of the patch whereas sensitization mostly leads to an extending reaction, often rounded. The distinction would be missed if circular patches are used. Such advice ought not to be dis- missed as merely anecdotal the authors, in the course of carrying out many thousands of patch tests, have accumulated a wealth of experience which is now made available to every- one. Rather less than half the pages are devoted to methodology, the remain- der being mainly concerned with the current 'standard tray' of twenty relatively common sensitizers listed by the International Contact Dermatitis Research Group and going into con- siderable detail to show possible sources of exposure to these and chemically-related substances. In treating an individual patient, the demonstration of a positive patch test response is only part of the story the next stage is to identify opportunities for exposure to the allergen and to show that avoidance of contact leads to relief of the skin condition... only then, incidentally, may the correctness of the patch-test diagnosis be taken as confirmed. The snag is that a standard array of common sensitizers becomes out- dated fairly quickly. So do references to uses of chemicals included in the tray. This part of the book cannot therefore retain its usefulness indefi- nitely but presumably revised editions will follow when necessary. Most of the contents insofar as they relate to the problems of individual patients, will not be directly appli- cable to the cosmetic scientist's work. Good advice abounds nevertheless, e.g. suggestions for non-irritating, non- sensitizing solvents for general patch- testing use. One of our main problems is not answered, namely what action to take, if any, following the demon- stration of positive allergic patch-test responses to our formulations in one or two patients. Should we regard these patients as odd and forget about them or should the formulation be deemed obnoxious and in need of alteration? A book such as the one now being reviewed will at least provide some of the underlying knowledge on the basis of which we may attempt to draw rational conclusions. N. G. VAN ABBi•