Anaphylaxis By James Fernandez, MD, PhD, Cleveland Clinic Lerner College of Medicine at Case Western Reserve University Reviewed / Revised Oct 2022 View Patient Education Etiology Pathophysiology Symptoms and Signs Diagnosis Treatment Prevention Key Points More Information Anaphylaxis is an acute, potentially life-threatening, IgE-mediated allergic reaction that occurs in previously sensitized people when they are reexposed to the sensitizing antigen.