Angioedema is a swelling that is similar to hives, but the swelling is under the skin instead of on the surface.

Hives are often called welts. They are a surface swelling. It is possible to have angioedema without hives.

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 most 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, and milk)
• Insect bites
• Medicines (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.

The health care provider will look at your skin and ask you if you have been exposed to any irritating substances. A physical exam might reveal abnormal sounds (stridor) when you breathe in if your throat is affected.

The health care provider may perform blood tests or allergy testing.

Mild symptoms may not need treatment. Moderate to severe symptoms may need to be treated. Breathing difficulty is an emergency condition.

People with angioedema should:

• Avoid any known allergen or trigger that causes their symptoms
• Avoid any medicines, herbs, or supplements that are not prescribed by a health care provider

Cool compresses or soaks can provide pain relief.

Medications used to treat angioedema include:

• Antihistamines
• Anti-inflammatory medicines (corticosteroids)
• Epinephrine shots (people with a history of severe symptoms can carry these with them)
• Inhaler medicines that help open up the airways
• Ranitidine (Zantac)

If the person has trouble breathing, seek immediate medical help. A severe, life-threatening airway blockage may occur if the throat swells.

Angioedema that does not affect the breathing may be uncomfortable, but is usually harmless and goes away in a few days.

Call your health care provider if:

• Angioedema does not respond to treatment
• It is severe
• You have never had angioedema before

Go to the emergency room or call the local emergency number (such as 911) if you have:

• Abnormal breathing sounds (stridor)
• Difficulty breathing
• Fainting
• Wheezing

Dreskin SC. Urticaria and angioedema. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier;2011:chap 260.

Wasserman SI. Approach to the person with allergic or immunologic disease. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier;2011:chap 257.