It is used for the rapid relief of severe allergic reactions, such as anaphylaxis, which is a potentially life-threatening condition. Anaphylaxis is a severe allergic reaction that can cause a range of symptoms, including difficulty breathing, rapid heartbeat, and low blood pressure. It works by blocking the effects of histamine, a chemical released by the body during an allergic reaction & reduces the symptoms of an allergic reaction, such as itching, swelling & redness.