[Drug allergy].

Adverse reaction to drugs are classified as immunological and non-immunological. It is consider that one to five percent of the general population reactions to drugs. Allergic reactions are the most intense and dangerous, but they represent only five to ten per cent of all of them. Immunological adverse reactions may be induced by the drug or by their metabolites. There are risk factors to induced allergic reactions such as doses, administration time and way of administration. The four mechanism of damage from Gell and Coombs are discussed regarding to drugs, stressing the penicillin issue. Other common drugs reactions in the diary practice are cutaneous reactions with unknown immunological mechanism as it happens in febrile mucocutaneous syndrome and the phototoxic and photoallergic reactions. Pseudoallergic or "anaphylactoid" reactions have signs and symptoms like those of anaphylaxis, but the mechanism of damage is not immunological, as with local and general anesthetics and radiopaque media. Treatment for any adverse events is to stop the administration as soon as possible. The drug of choice is 1:1000 subcutaneous adrenaline besides colloid solutions, steroids and antihistaminics.