This document discusses anaphylaxis, a severe and potentially life-threatening allergic reaction. It defines anaphylaxis and explains that it is a type 1 hypersensitivity reaction caused by the immune system overreacting to normally harmless substances. Symptoms can affect multiple body systems like the skin, respiratory and digestive systems. Diagnosis is based on clinical criteria of symptoms occurring within minutes or hours of exposure. Treatment involves epinephrine and other emergency measures, with prevention being avoidance of triggering allergens.