What causes angio-oedema?
In most cases, there is no known cause and it is not clear why it occurs. This is called 'idiopathic angio-oedema'. Although the cause is not clear, in up to half of cases there is a link to an auto-immune disorder, for example, chronic urticaria, systemic lupus erythematosus (SLE), etc. About half of people who have chronic urticaria also have regular episodes of angio-oedema. In some cases there are known 'triggers' that can cause the release of histamine which leads to tissue swelling of angio-oedema. These are:
Allergic reactions
Some people develop angio-oedema as part of an allergy reaction. Something triggers the immune system which triggers mast cells to release histamine. In effect, it is a bit like the immune system 'over reacting'. For example:
- Allergy to foods, for example, nuts, shellfish, milk, eggs.
- Allergy to drugs, for example, penicillin, aspirin.
- Allergy to latex, insect bites or stings.
The symptoms that may develop with an allergic reaction can vary. For example:
- Some people develop an urticarial rash.
- Some people develop angio-oedema.
- Some people develop an urticarial rash and angio-oedema.
- Some people develop a very severe reaction called anaphylaxis. This usually includes an urticarial rash, angio-oedema, and other symptoms such as low blood pressure, severe breathing problems, and collapse. Anaphylaxis is rare, but is the most serious type of allergic reaction and can be fatal unless promptly treated.
- Various other symptoms can develop to localised allergies. For example, nasal symptoms if you are allergic to pollen (hay fever), etc.
Non-allergic drug reaction
Some drugs (medicines) can cause angio-oedema as a side-effect. For example, angiotensin converting enzyme (ACE) inhibitors and angiotension-II receptor antagonists (AIIRAs). These medicines are commonly used to treat heart problems and high blood pressure.
Hereditary
Some people inherit a tendency to develop episodes of angio-oedema. This is due to a lack of an enzyme called C1 esterase. This condition is called 'hereditary C1 esterase deficiency'. About 1 in 50,000 people inherit the gene for C1 esterase deficiency. Children born to people with this condition have a 50:50 chance of inheriting the condition. Although it is hereditary and most cases first develop in childhood, in some cases the angio-oedema may first develop in early adulthood.
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