Background: Drugs are responsible for 40% to 60% of anaphylactic reactions treated in the emergency department. A global research agenda to address uncertainties in anaphylaxis includes studies that identify factors associated with morbidity and mortality., Objective: The present study investigated drug-induced anaphylaxis, etiologies, aggravating factors, and treatment., Methods: A total of 806 patients with adverse drug reactions were screened, and those who had a clinical diagnosis of anaphylaxis were included in the study. Clinical and demographic characteristics of anaphylaxis were described, including etiologies, pathophysiologic mechanisms involved in the reactions, and a personal history of atopy and asthma. Factors associated with disease severity also were identified., Results: Anaphylaxis was diagnosed in 117 patients (14.5%). The etiologies were defined in 76% of the cases, nonsteroidal anti-inflammatory drugs being the most frequent. Seventy-eight patients (66.7%) reported a previous reaction to the drug involved in the current reaction or to a drug from the same class and/or group. Epinephrine was used to treat 34.2% of patients who presented with anaphylaxis, and 40.8% of those with anaphylactic reactions with cardiovascular involvement. IgE-mediated reactions were associated with greater severity, manifested by the rates of cardiovascular dysfunction, hospitalization, and use of epinephrine., Conclusions: The prevalence of anaphylaxis is high in patients who seek medical assistance for drug reactions, but its diagnosis is missed in emergency services, and adrenaline is underused. Drugs were prescribed to many patients despite a history of previous reaction. Nonsteroidal anti-inflammatory drugs were implicated in most cases of anaphylaxis induced by drugs, and IgE-mediated reactions were less frequent but more severe., (Copyright © 2014 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)