[Adverse drug reactions and the skin--from trivial to fire signal]

Adverse drug reactions are a common medical problem. Especially hypersensitivity reactions are mostly impressive and unsettling due to their nature of being not dose-dependent and non-predictable. Clinical manifestations of the skin comprise manifold appearances from mild macular exanthems to bullous eruptions, and urticaria, angioedema to anaphylaxis. Systemic hypersensitivity reactions can affect nearly all internal organs and cells. Characteristic clinical danger signs for severe allergic drug reactions, for immediate type as well as for delayed type manifestations, help to recognise the incipient allergic drug reaction, to stop the further administration of the potential elicitor/allergen and to start therapeutic actions. It is essential for the success of a further allergologic work-up of such reactions to describe and document accurately the morphologic characteristics of the skin and other organ manifestations and the exact time course of medication intake and development of the clinical adverse reaction. This facilitates the choice of adequate diagnostic measures and the interpretation of the respective results.