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.
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".
Some medicines can cause angioedema – even if you're not allergic to the medication.
The swelling may occur soon after you start taking a new medication, or possibly months or even years later.
Medications that can cause angioedema include:
- angiotensin-converting enzyme (ACE) inhibitors, such as enalapril, lisinopril, perindopril and ramipril, which are used to treat high blood pressure
- ibuprofen and other types of NSAID painkillers
- angiotensin-2 receptor blockers (ARBs), such as andesartan, irbesartan, losartan, valsartan and olmesartan – another medication used to treat high blood pressure
Angioedema caused by medication is known as "drug-induced angioedema".
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:
- an injury or infection
- surgery and dental treatment
- certain medications, such as the contraceptive pill
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 50% chance of passing it on to your children.
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:
- anxiety or stress
- minor infections
- hot or cold temperatures
- strenuous exercise
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".