Evaluation of anaphylaxis is a common reason for emergency department referral to an allergist. Establishing unified diagnostic criteria has been an evolving process with the most recent definition proposed by the Second Symposium on the Definition and Management of Anaphylaxis convened by the National Institute of Allergy and Infectious Disease and the Food Allergy and Anaphylaxis Network. Proper identification of these patients in the emergency department allows for the opportunity to dispense potentially life-saving epinephrine autoinjectors, provide education, and allergist referral. Future epidemiological studies are likely to be impacted as the definition of anaphylaxis becomes more unified.