Angioedema is a swelling, similar to hives, but the swelling is beneath the skin rather than on the surface. Hives are often called welts. They are a surface swelling. It is also possible to have angioedema without hives.

See also: Hereditary angioedema

Angioneurotic edema; Welts

Angioedema may be caused by an allergic reaction. During the reaction, histamine and other chemicals are released into the bloodstream. The body releases histamine when the immune system detects a foreign substance called an allergen.

In many cases, the cause of angioedema is never found.

The following may cause angioedema:

• Animal dander (scales of shed skin)
• Exposure to water, sunlight, cold or heat
• Foods (such as berries, shellfish, fish, nuts, eggs, milk, and others)
• Insect bites
• Medications (drug allergy), such as antibiotics (penicillin and sulfa drugs), nonsteroidal anti-inflammatory drugs (NSAIDs), and blood pressure medicines (ACE inhibitors)
• Pollen

Hives and angioedema may also occur after infections or with other illnesses (including autoimmune disorders such as lupus, and leukemia and lymphoma).

A form of angioedema runs in families and has different triggers, complications, and treatments. This is called hereditary angioedema, and it is not discussed in this article.

Review Date: 05/16/2010
Reviewed By: David C. Dugdale, III., MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)