RESUMEN
Anaphylaxis must always be considered a medical emergency. While classic anaphylaxis needs specific antigen to trigger IgE antibody-mediated reaction, idiopathic anaphylaxis spontaneously occurs with no external allergen. Anaphylactoid are not mediated by antigen-antibody but result from substances acting directly on mast cells and basophils. Incidence of anaphylaxis is 21 per 100,000 person-years with fatality in about 0.65% of cases. Food is the most frequent cause of anaphylaxis in children while insect sting is the most common cause in adults. Epinephrine is the first pharmacological treatment. Secondary measures include circulatory support, H1 and H2 antagonists, bronchodilators if necessary and probably corticosteroids. Since life-threatening manifestations may recur during the recurrent phase, it may be necessary to observe the patients for up to 48 hours after apparent recovery from an anaphylactic episode.