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 .

Often the cause of angioedema is never found.

The following items may cause angioedema.

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

Hives and angioedema may also occur after infections or with other illness (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 here.

The main symptom is the sudden development of swelling. You may also develop welts.

The welts usually occur around the eyes and lips. They may also be found on the hands, feet, and throat. They may form a line or be more spread out.

The welts are painful and may be itchy. They turn pale and swell if irritated.

Other symptoms may include:

• Abdominal cramping
• Breathing difficulty
• Swollen eyes and mouth
• Swollen lining of the eyes (chemosis )

The doctor 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 the throat is affected.

Rarely, the health care provider may perform allergy testing .

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

Cool compresses or soaks can provide pain relief.

Medications used to treat angioedema include:

• Antihistamines
• Anti-inflammatory medicines (corticosteroids)
• Cimetidine (Tagamet)
• Epinephrine
• Terbutaline (a bronchodilator)

If the person has trouble breathing, seek immediate medical help.

See: Breathing difficulties - first aid

At the hospital, a tube may be placed in the throat to keep the airway open.

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

• Anaphylactic reaction
• Life-threatening airway blockage (if swelling occurs in the throat)

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

To prevent angioedema from coming back:

• Avoid irritating the affected area
• Avoid temperature extremes
• Stay away from known allergens

Never take medications that are not prescribed for you.

Kaplan AP. Angioedema. J Am Acad Dermatol. Sept 2005; 53(3): 373-88.

Habif TP. Clinical Dermatology. 4th ed. St. Louis, Mo: Mosby; 2004:129.

Marx J. Rosen's Emergency Medicine: Concepts and Clinical Practice. 6th ed. St. Louis, Mo: Mosby; 2006:1834-1835.

Temino VM, Peebles RS Jr. The spectrum and treatment of angioedema. Am J Med. 2008;121:282-286.