Epinephrine is a medication used to treat severe allergic reactions (anaphylaxis) or sudden asthma attacks. It works by reducing the effects of an allergic reaction, such as trouble breathing or swelling of the face, lips, and throat. It also increases heart rate and narrows blood vessels, which helps stabilize blood pressure. Epinephrine injection is usually given by a healthcare provider in a hospital or clinic setting, but it can also be self-administered in an emergency using a prefilled automatic injection device containing a solution (liquid) or vials to inject subcutaneously (under the skin) or intramuscularly (into the muscle). Epinephrine injection is also used to treat life-threatening low blood pressure associated with septic shock in hospitalized adults. Epinephrine is in a class of medications called alpha- and beta-adrenergic agonists (sympathomimetic agents) and is typically released when the body is under stress.