Anaphylaxis is a life-threatening clinical condition that results from the activation of mast cells/basophils, inflammatory pathways, or both. It can be specific (allergic), or non-specific (non-allergic). Most anaphylaxis are mediated by IgE, but there are also some mediated by IgM and complement activation. Incidence is about 1:10,000 anesthesia. Recent studies show that the drugs or substances mostly implicated in producing perioperative anaphylaxis are: neuromuscular blockers (60.6%), antibiotics (18.2%), patent blue dye (5.4%) and latex (5.2%). However, all drugs and substances used during anesthesia and surgery, perhaps with the sole exception of inhalation agents and crystalloids, have been reported as potentially causes of anaphylaxis. The clinical presentation is multisystemic, producing signs and symptoms mainly on skin, respiratory, cardiovascular, gastrointestinal and central nervous systems. In its advanced phase, it may evolve to anaphylactic shock, causing tissue hypoperfusion and leading to altered cell integrity and multiple organ failure, associated with high mortality. Diagnosis is based on clinical presentation (history and clinical manifestations), biological evidence (serum tryptase levels, serum histamine levels and search for specific IgE) and allergological evidence (skin tests, provocation test, mediator release tests and tests of activation of basophils). Treatment include 3 stages: general measures, first-line or primary treatment and second-line or secondary treatment. General measures consist of: Trendelenburg position, invasive monitoring (according to the severity of the clinical presentation), 100% oxygen administration, discontinuation of drugs and/or suspected agents and asking for help. The primary treatment is epinephrine in doses proportional to the clinical manifestations, airway support, 100% oxygen and aggressive resuscitation with intravenous fluids. Secondary treatment includesadministration of bronchialodilators, corticosteroids, and antihistamines.