Preface by Dr Richard Rycroft

The eighteenth-century author Samuel Johnson was once goaded by his biographer James Boswell into an uncharacteristic lapse in modesty about his painstaking Dictionary of the English Language. Replying to Boswell's suggestion that the great man might not have known what he was taking on, Johnson growled, "I knew very well what I was undertaking, and very well how to do it, and have done it very well". Anton de Groot could justly claim the same for his Patch Testing and, like Johnson, he has also had the stamina to see his masterwork through more than one new edition.

Knowing his second edition to have been overtaken by continuing discovery and innovation, de Groot has applied himself once again to updating this essential aid to the investigation of contact dermatitis. While using every electronic resource at his disposal to compile this new data, it has been a book, rather than a data base, that has emerged at the end of his labours, and for this I suggest you should be mightily relieved. "The report of my death was an exaggeration," wrote Mark Twain in the New York Journal of 2 June 1897, and we may happily feel the same by now about the much-prophesied death of the printed book. The information in Patch Testing needs not only to be comprehensive and accurate: most users also require that it can be looked-up in a flash, by everyone needing to, anywhere in a dermatology unit. For the time being, only a clearly laid-out handbook will do, and here you have it.

Drawing on his own clinical experience, de Groot is prepared, in cases of genuine doubt over patch test concentration and vehicle, to leave the reader to decide which recommendation to follow. All available information having been provided, it is right that the clinician's own assessment of the reliability of the sources of advice quoted, and of the likely degree of sensitization of the particular patient being patch tested, should be allowed to have the final say. But this is also the text of a thoughtful scientist. When sound advice is difficult to give, the data are provided on which to base further work: small numbers of control subjects, for example, may suggest the need for larger numbers to be tested. Thus, this is a reference work to encourage, rather than to stifle, further clinical research on contact dermatitis.

Ultimately, the strength of the book lies in the character of the author himself. De Groot has relentlessly hunted down every last contact allergen and every last reference to its patch test concentration and vehicle. You may be sure that if it is not in here, then it is most unlikely to be anywhere. The author's months of fruitful toil will save you hours of fruitless searching, and for that both you and your patients can only be the grateful beneficiaries

Richard Rycroft
Honorary Consultant Dermatologist
St John's Institute of Dermatology
London