Diagnostic approach in allergic and irritant contact dermatitis

Contact dermatitis is a highly frequent disease with a significant impact on the quality of life of the affected patients and a relevant socioeconomic impact. According to the pathophysiological mechanisms involved, two major types of contact dermatitis may be recognized: irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD). The two types may, and often do, coexist. Differentiating between ICD and ACD is often difficult in the clinical setting. The basis for a diagnosis of either ICD or ACD is mainly established by a comprehensive clinical history and physical examination, as well as by performing appropriate diagnostic patch testing. The only useful and reliable method for the diagnosis of ACD remains the patch test. Positive patch test results, the current and/or past relevance of which has to be assessed, are confirmative of contact sensitization. Additional tests, such as the repeated open application test or the provocative use test, are sometimes necessary to confirm a causal relationship. This algorithmic diagnostic approach will allow the adoption of rational measures of allergen or irritant avoidance and the implementation of realistic patient information and education.