Book excerpt: Knowledge in the field of allergic contact dermatitis has grown to a great extent, due to recent advances in the chemical, immunological and clinical fields. These advances include the improved techniques of patch testing and prick testing, e.g. additional tests such as open, semi-open, repeated open application test (ROAT) and use tests, photopatch tests, atopy patch tests and provocative tests. Further, due to the ongoing changes in our environment, the series of patch tests – the so-called standards – are also regularly renewed. This new edition is completely revised, updated and expanded, with more colour illustrations. It is a universally useful and superb guide in the management of positive and negative patch test and prick test reactions, for all practicing dermatologists, from the beginner to the well-trained expert.