Health answers: What is anaphylaxis?
Anaphylaxis is a severe and potentially life-threatening allergic reaction. Compared with other allergies, “the scale is much greater,” says Dr. David Hong, an allergist and immunologist at Brigham and Women’s Hospital. It is systemic (involving the entire body) rather than localized to one spot, and usually happens suddenly. The most common triggers are specific foods (nuts, shellfish, dairy products), insect bites and stings, and medications.