Angioedema can be a reaction to a drug or other substance (trigger), a hereditary disorder, a rare complication of cancer, or an immune disorder, but sometimes the cause is not known.
Angioedema may involve swelling in the face, throat, digestive tract, and airways.
Antihistamines can relieve mild symptoms, but if angioedema makes swallowing or breathing difficult, prompt emergency treatment is needed.
(See also Overview of Allergic Reactions.)
Angioedema often occurs with hives, which causes itching. Both hives and angioedema involve swelling, but in angioedema, the swelling is deeper (under the skin) than it is with hives, and it may not itch.
There are rare hereditary or acquired forms of angioedema. These forms are caused by a deficiency or malfunction of a substance called C1 inhibitor, which is part of the immune system. Hereditary angioedema and acquired angioedema resemble angioedema caused by an allergic reaction. However, hives do not develop, and the cause is different.
Angioedema may be acute or chronic.
Acute angioedema develops suddenly after exposure to a trigger.
Common triggers are
Many drugs, such as aspirin, other nonsteroidal anti-inflammatory drugs (NSAIDs), angiotensin-converting enzyme (ACE) inhibitors, and certain opioids (called opiates) such as morphine and codeine
Insect stings or bites
Allergy injections (allergen immunotherapy)
Certain foods—particularly eggs, fish, shellfish, nuts, and fruits
Angioedema without hives is sometimes caused by ACE inhibitors, which are used to treat high blood pressure and heart failure. When ACE inhibitors are the cause, the face and upper airways are most commonly affected, but the intestine may be affected.
Eating even a tiny amount of some foods can suddenly result in angioedema. But with other foods (such as strawberries), these reactions occur only after a large amount is eaten.
Also, angioedema sometimes occurs after a substance that can be seen on x-rays (radiopaque contrast agent) is used during an imaging test.
Angioedema can be chronic, recurring over weeks or months. The cause is usually unknown, but it may be repeated, unintentional intake of a substance, such as penicillin in milk or a preservative or dye in foods. Use of certain drugs, such as aspirin, other NSAIDs, or opioids, can also cause chronic angioedema.
Chronic angioedema that occurs without hives may be hereditary or acquired angioedema.
However, usually when angioedema recurs (with or without hives), no specific cause is identified—called idiopathic angioedema.
In angioedema, swelling may not be equal on both sides of the body, and it can be mildly painful. It can affect the back of the hands or feet, eyelids, tongue, face, lips, or genitals. Sometimes the membranes lining the mouth, throat, and airways swell, making swallowing or breathing difficult.
Occasionally, the digestive tract is involved, resulting in nausea, vomiting, crampy abdominal pain, or diarrhea.
Many people also have hives. Hives usually begin with itching. Typically, crops of hives then come and go. One spot may remain for several hours, then disappear, and later, another may appear elsewhere. After the hive disappears, the skin usually looks completely normal.
People may have an anaphylactic reaction (a sudden, widespread, sometimes life-threatening allergic reaction). Blood pressure may become dangerously low (shock).
People should see a doctor immediately if they develop angioedema. If the cause is a bee sting, they can obtain advice about treatment if another bee sting occurs.
The cause of angioedema is often obvious, and tests are seldom needed because the reactions usually resolve and do not recur.
If angioedema recurs and the cause is not clear, doctors ask people about all the drugs they are taking and all food and drink they are consuming. If the cause is still not clear, particularly if people have no hives or if family members have angioedema, doctors may do tests for hereditary or acquired forms of angioedema.
If the cause of angioedema is obvious, people should avoid it if possible. If the cause is not obvious, all nonessential drugs should be stopped until symptoms resolve.
For mild angioedema with hives, taking antihistamines partially relieves the itching and reduces the swelling. Corticosteroids, taken by mouth, are prescribed for severe symptoms when other treatments are ineffective, and they are given for as short a time as possible. When taken by mouth for more than 3 to 4 weeks, they have many, sometimes serious side effects. Corticosteroid skin preparations (such as creams, ointments, and lotions) do not help.
For angioedema without hives (as when caused by an ACE inhibitor or a hereditary form of angioedema), antihistamines, corticosteroids, and epinephrine may not help. If the cause is an ACE inhibitor, symptoms usually resolve about 24 to 48 hours after stopping the drug. If symptoms do not resolve, are severe, or are getting worse, doctors sometimes give fresh frozen plasma or certain drugs such as ecallantide. Purified C1 inhibitor derived from human blood can also be used.
For idiopathic angioedema, a high dose of an antihistamine, taken by mouth, may help.
If severe angioedema results in difficulty swallowing or breathing or in collapse, prompt emergency treatment is necessary. Doctors must then open the person's airway by doing one or both of the following:
If the airway closes too fast, doctors may have to make a small incision in the skin over the windpipe and insert a breathing tube.
People who have severe reactions should always carry a self-injecting syringe of epinephrine to be used immediately if a reaction occurs. Antihistamine pills may also help, but epinephrine should be injected before taking antihistamine pills.
After a severe allergic reaction, such people should go to the hospital emergency department, where they can be checked and treated as needed.