It is now clear that the prevalence of allergic diseases is increasing everywhere. For example, the cumulative prevalence of allergic diseases places them second as a cause of morbidity in the American population. It has been estimated that 10% of the US populat ion will have asthma or eczema, 10-15% allergic rhinitis, and 10-15% a drug allergy during their lifetimes. Experience in Emergency Departments reflects this trend. The Emergency Room (ER) is frequently a place of recourse for patients having an allergic reaction. Many have consulted a physician or taken an antihistamine before coming to an ER. From the ER physician's point of view, the term "allergy" is often misused by patients, especially when they have a skin problem. For example, patients coming to the ER with a pruritic rash, when questioned commonly say, "It is for an allergy," sometimes reflecting what their physician had previously told them. The two most important allergic emergencies seen in the ER are anaphylaxis and severe asthma. Since severe asthma is covered in another article in this issue, the present discussion will be limited to anaphylaxis--and its variants--as seen in the ER.