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Drug-induced eruptions or iatrogenic skin reactions are cutaneous eruptions linked to a medicinal product or drug intake. Such reaction are very common, and it has been estimated that 3% of hospitalized patients will experience a cutaneous eruption linked to drug intake during their hospitalization. The clinical presentation and severity of drug-induced eruptions are extremely variable.

Severe forms, which can, in some cases, be life-threatening :

•  Stevens Johnson and Lyell syndromes (toxic epidermal necrolysis or TEN), which are characterized by extensive epidermal detachment;
• DRESS (drug rash with eosinophilia and systemic symptoms) or drug hypersensitivity syndrome, which is characterized by a cutaneous eruption without detachment, but with a severe systemic involvement;
• AGEP (acute generalized exanthematous pustulosis), which is characterized by a pustular eruption in the body folds combined with a generalized eruption.

Pathophysiologically, these drug-induced eruptions should be differentiated from angioedema, Quincke's edema, and anaphylactic shock, which are type-I immediate reactions to drugs (Gell and Coombs classification).
Mild drug-induced eruptions, which include:

• simple erythematous eruptions characterized by maculopapular exanthema without any skin detachment or systemic involvement, but which are always worrying sign;
• simple outbreaks of urticaria;
• photosensitivity eruptions linked to exposure to UV light;
• fixed drug eruptions, which constitute a very localized and mild form of skin eruption.