Care and therapy of patients experiencing an anaphylactic reaction should be known by the physicians working in the emergency medical unit or in pre-hospital care. The epidemiology of these reactions varies according to the countries. The main aetiologies are due to food, hymenoptera or drugs. The clinical scale proposed by Ring and Messmer aims to classify the reactions in 4 grades according to their severity and is useful to stratify therapy. According to the grade of the reaction, the drug of choice for the treatment of anaphylaxis is epinephrine associated to vascular expansion. Anaphylaxis during pregnancy is described. Patients who experienced an immediate hypersensitivity reaction should undergo an allergological investigation to prove the immune mechanism and to identify the culprit allergen. Reporting to the Drug Safety Monitoring Authorities when a drug is implicated should not be forgotten.