This chapter discusses the diagnosis, evaluation and management of anaphylaxis. Anaphylaxis is a clinical diagnosis. However, some laboratory tests may be helpful in evaluating the severity of the reaction, guide treatment, and rule out concurrent emergencies. Epinephrine is the primary treatment of anaphylaxis. For typical presentations of anaphylaxis, epinephrine should be administered intrasmuscularly (IM); the adult dose is 0.3-0.5 mL of 1:1000 concentration. Much confusion exists over proper epinephrine dosing: extreme care must be taken not to mistakenly administer the cardiac arrest dose (1 mg of 1:10,000 concentration) in anaphylaxis, as it may lead to potentially lethal cardiac complications. Most patients with mild to moderate anaphylaxis who respond appropriately to initial treatment may be discharged home. Additional crystalloid should be considered; colloid solutions such as 5% albumin may also be considered given the increased vascular permeability involved in anaphylaxis.