Commonly caused by antibiotics (PCN causes 95% of fatal reactions), anesthetics, radiocontrast (1:1000 to 1:14,000 injections, 10% of which are fatal [J Crit Illness 8: 332, 1993]), various foods, and insect stings. Presentation can be mild (flushing, rash, urticaria, abdominal cramping, diarrhea) or severe (angioedema, laryngeal edema, bronchospasm, hypotension). Treat with ABCs, 0.3 – 0.5 mL of 1:1000 epinephrine SQ, rapid volume infusion (Marino says that colloids are preferred), steroids (methylprednisolone 1-2 mg/kg IV for severe reactions or prednisone 1 mg/kg PO for mild reactions), 25-75 mg diphenhydramine PO/IM/IV, 50 mg ranitidine IV, albuterol if wheezing, possibly aminophylline if bronchospasm persists. Monitor and control the airway! If patient does not respond to epinephrine or is on β-blockers, consider glucagon 1 mg IV push followed by 1-2 mg/h drip. Have low threshold for surgical airway.