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Angioedema is a condition characterized by swelling and the formation of welts (raised marks) on the skin. It is similar to hives, except the welts are larger and form at a deeper layer in the skin. This causes swelling of the skin that usually affects the face near the eyes and mouth, as well as the hands and feet. However, swelling can also occur inside the throat, which can cause difficulty breathing.

There are two main types of angioedema: hereditary and allergic. Hereditary angioedema is caused by an abnormality of the immune system. It is an inherited disorder that results from the absence of or a defect in a protein called C1 inhibitor. This absence or defect affects the blood vessels, leading to symptoms such as rapid swelling of the hands, feet, limbs, face, intestinal tract or airway (larynx or trachea).

However, the term “angioedema” most often refers to the more common, allergic form of the disease. Like other allergic conditions, allergic angioedema symptoms are triggered by the release of histamine and other biochemicals in the body. Many different allergens can start this process, including foods, medications (particularly aspirin), cosmetics, soaps and detergents.

Angioedema may also be categorized as idiopathic. Idiopathic angioedema is caused by unknown factors or by exposure to certain medications. In over half the cases, the trigger for angioedema is unknown.

An episode of angioedema typically lasts from a few hours to a few days. For most people, angioedema is unpleasant, but does not cause long-term, serious harm or scarring.