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Causes

Angioedema can have several different causes, but in many cases the exact cause is unknown.

Some of the main causes of angioedema are outlined below.

Allergies

Angioedema is often the result of an allergic reaction.

This is where the body mistakes a harmless substance, such as a certain food, for something dangerous. It releases chemicals into the body to attack the substance, which cause the skin to swell.

Angioedema can be triggered by an allergic reaction to:

Angioedema caused by allergies is known as allergic angioedema.

Medicine

Some medicines can cause angioedema – even if you're not allergic to the medicine.

The swelling may occur soon after you start taking a new medicine, or possibly months or even years later.

Medicines that can cause angioedema include:

Angioedema caused by medicine is known as drug-induced angioedema.

Genetics

Rarely, angioedema occurs because of a genetic fault that you inherit from your parents.

The fault affects the gene responsible for the production of a substance called C1 esterase inhibitor. If you don't have enough of this, the immune system can occasionally "misfire" and cause angioedema.

The swelling may happen randomly, or it may be triggered by:

How often the swelling occurs can vary. Some people experience it every week, while in others it may occur less than once a year.

Angioedema caused by a genetic fault is known as hereditary angioedema. If you have it, you have a 1 in 2 chance of passing it on to your children.

Unknown cause

In many cases, it's not clear what causes angioedema.

One theory is that an unknown problem with the immune system might cause it to occasionally misfire.

Certain triggers may lead to swelling, such as:

In very rare cases, the swelling may be associated with other medical conditions, such as lupus or lymphoma (cancer of the lymphatic system).

Angioedema without a clear cause is known as idiopathic angioedema.