Drug Allergy and Cutaneous Adverse Reactions.

Allergy or hypersensitivity to drugs often affects the skin and sometimes also mucosa. While immediate type reactions show a rather homogeneous pattern, delayed type reactions reveal a high variability. In both cases it may not always be easy to differentiate drug reactions from non-drug-induced skin conditions. Furthermore, the different types of cutaneous adverse reactions may be difficult to distinguish in the beginning. This accounts predominately for delayed hypersensitivity reactions that can occur after a variety of medications and present with manifold lesions. Most of these cutaneous adverse reactions are mild, but some are severe with high morbidity and mortality. In the clinical setting, it is important to recognize the signs that point to a more severe condition early on in order to initiate appropriate management. In addition, it is crucial to identify the potentially culprit medication on the basis of a detailed medication history and by evaluating the relevant exposure times of certain drugs that differ substantially between the various reaction types. After the acute stage of the adverse reaction is managed successfully, further allergologic testing may be undertaken to confirm the offending drug.