According to different estimations, the systemic or topical administration of drugs is the 2nd or 3rd identified cause of urticarias. Urticaria may be the leading symptom of drug-induced immuno-allergic reactions such as anaphylaxis or serum sickness. More often, it is the manifestation of non-immune reactions by drug-induced direct release of histamine, activation of complement or enzymatic impairment of the metabolism of arachidonic acid derivatives. Skin tests may be helpful for the demonstration of the responsibility of drugs in the immuno-allergic reactions. Whatever the mechanism may be, one should dissuade from provocation reintroduction of the suspected drug without an extreme wariness.