Epicutaneous patch testing.

Epicutaneous patch testing is still regarded as the best method of diagnosing allergic contact dermatitis. The present patch test technique is the result of a continuous process of development and improvement since its first application in the late 19th century. During the last decades of the 20th century a lot of effort was put into standardization of materials and methods used in patch testing. Patch tests can be used to confirm a suspected allergic contact dermatitis and either to recommend avoidance of particular products or to recommend alternative products in a particular patient. The true rate of clinically relevant hypersensitivity in positive patch test reactions remains to a great extent unknown. The ideal patch test should cause as few adverse reactions as possible, but a lot of adverse reactions have been described. How-ever, it has to be noted that the overall risk-benefit equation of patch testing is in favor of the benefit, if performed correctly and with the proper indications. A careful history taking and attention to the clinical picture are key actions to facilitate the interpretation of the clinical relevance of the epicutaneous patch test results.