Causes of angioedema

Angioedema is often caused by a problem with the immune system, although there are many cases where no cause can be identified.

Allergic angioedema

Normally, your immune system protects your body from illness and infection by detecting germs in the blood and producing white blood cells and chemicals to destroy them and prevent any infection spreading.

In allergic angioedema, your immune system mistakenly reacts like this to harmless substances in your blood. Your body produces the chemical histamine, which causes the blood vessels in the area to expand, leading to swelling of the skin.

Substances known to trigger allergic angioedema include:

Idiopathic angioedema

Cases of angioedema without an identifiable cause are known as idiopathic angioedema. It may be that a problem with the immune system sometimes causes it to ‘misfire’.

If you have idiopathic angioedema, certain triggers may lead to swelling, such as:

  • stress
  • minor infections
  • alcohol
  • caffeine
  • spicy food
  • overheating (such as from a hot bath or shower)
  • wearing tight clothes

Avoiding these triggers whenever possible may improve your symptoms.

Drug-induced angioedema

Some medications can cause angioedema. Angiotensin-converting enzyme (ACE) inhibitors, which are used to treat high blood pressure (hypertension), are usually responsible.

It is estimated that around 1-5% of people taking ACE inhibitors will develop drug-induced angioedema. Black people being treated with ACE inhibitors are three to four times more likely to develop this side effect than white people.

About one in four cases of drug-induced angioedema occurs during the first month of taking an ACE inhibitor. The remaining cases develop many months or even years after treatment begins.

While they are useful in lowering blood pressure, ACE inhibitors can sometimes disrupt the ‘chemical balance’ and trigger an episode of severe swelling.

Less common causes of drug-induced angioedema include:

Hereditary angioedema

Hereditary angioedema is caused by a genetic mutation (a change in the DNA) in the C1-esterase inhibitor (C1-INH) gene. Genes are single units of genetic material that code for characteristics such as eye and hair colour.

As a result of the mutated C1-INH gene, the body does not make enough C1-INH protein. This protein plays an important role in regulating the immune system. Without enough C1-INH protein, the immune system can misfire and trigger the symptoms of angioedema.

Certain factors are thought to trigger hereditary angioedema, such as:

  • trauma, including surgery or infection
  • the oral contraceptive pill
  • pregnancy

The mutated C1-INH gene is passed down through families in a pattern known as autosomal dominant inheritance. This means that if you have hereditary angioedema, you have a 50% chance of passing it on to your children.

Published Date
2012-10-26 09:47:41Z
Last Review Date
2012-09-24 00:00:00Z
Next Review Date
2014-09-24 00:00:00Z


Diagnosing angioedema

Diagnosing angioedema is relatively straightforward, but tests are required to determine which type it is.

An examination of the affected skin by a doctor is usually enough to diagnose angioedema. You may also be asked about any associated symptoms, such as swelling of your throat or abdominal (tummy) pain.

Each type of angioedema requires different testing before it is diagnosed. These are detailed below.

Allergic angioedema

Your GP will ask whether you have recently been exposed to any common allergens (allergy-causing substances), such as nuts or latex. They will also ask whether you have a history of other allergic conditions, such as hives or asthma. People who have one allergic condition often develop other allergic conditions.

You will need to tell your doctor about all the medications that you are taking, including over-the-counter medication such as painkillers, herbal supplements and vitamins.

If you are having frequent episodes of angioedema, your GP may recommend that you keep a diary of your exposure to possible irritants.

If a diagnosis of allergic angioedema is suspected, you are likely to be referred to a specialist allergy or immunology clinic for further testing. Tests may include:

  • a skin prick test – your skin is pricked with a tiny amount of the suspected allergen to see whether there is a reaction
  • a blood test – a sample of your blood is tested to determine whether your immune system reacts to a suspected allergen

Read more about diagnosing allergies.

Drug-induced angioedema

If you are taking a medication that is known to cause drug-induced angioedema, your GP will withdraw that medication and prescribe an alternative. If you don’t have any further episodes of angioedema, a diagnosis of drug-induced angioedema can be made.

Hereditary angioedema

Hereditary angioedema can be diagnosed by using a blood test to check the level of proteins that are regulated by the C1-INH gene. A very low level would suggest a diagnosis of hereditary angioedema.

You may also be asked if you have a family history of hereditary angioedema.

The diagnosis and management of hereditary angioedema is highly specialised and should be carried out in a specialist immunology clinic.

Idiopathic angioedema

Idiopathic angioedema is usually confirmed by a process known as a ‘diagnosis of exclusion’. This means a diagnosis of idiopathic angioedema can only be made after all the above tests have been carried out and a cause has not been found. 

As angioedema can be associated with other medical problems, such as deficiency of iron, liver diseases, and problems with the thyroid gland, your doctor or specialist will undertake some simple blood tests to check for these conditions.

Published Date
2012-10-26 09:47:55Z
Last Review Date
2012-09-24 00:00:00Z
Next Review Date
2014-09-24 00:00:00Z



Angioedema is the swelling of the deeper layers of the skin, caused by a build-up of fluid.

The symptoms of angioedema can affect any part of the body, but swelling usually affects the:

  • eyes
  • lips
  • genitals
  • hands
  • feet

Many people with angioedema also have another condition called hives, which is also known as urticaria, welts or nettle rash. This is a raised, red and itchy rash that appears on the skin.

Read more about the symptoms of angioedema.

Why does angioedema happen?

The causes of angioedema depend on the type of condition you have. There are four main types of angioedema:

  • allergic angioedema – the swelling is caused by an allergic reaction, such as a reaction to peanuts, and sometimes occurs in combination with anaphylaxis
  • idiopathic angioedema – there is no known cause for the symptoms of swelling (although certain factors, such as stress or infection, may trigger the symptoms)
  • drug-induced angioedema – the swelling is a side effect of certain medications, most often angiotensin-converting enzyme (ACE) inhibitors
  • hereditary angioedema – the swelling is caused by ‘faulty’ genes that are inherited from a person’s parents

Read more about the causes of angioedema.

How common is angioedema?

Angioedema is quite a common condition which affects about 10-20% of people during their life, although some types are more common than others.

Food allergies, the main cause of allergic angioedema, are estimated to affect about 5-8% of children and 1-2% of adults.

It is not clear how common idiopathic angioedema is, as it can be misdiagnosed as allergic angioedema. However, long-lasting (chronic) idiopathic angioedema is estimated to affect 1 in 2,000 people.

Although estimates vary, ACE inhibitors are thought to cause drug-induced angioedema in around 1-5% of people who take them.

Hereditary angioedema is rare, only affecting between 1 in 10,000 and 1 in 50,000 people worldwide.


Diagnosing angioedema is relatively straightforward. Due to its distinctive appearance, a doctor should be able to recognise it after a physical examination.

Further tests, such as blood tests, may be required to determine the exact type of angioedema.

Idiopathic angioedema is only diagnosed if no cause can be found after testing.

Read more about diagnosing angioedema.

How is angioedema treated?

Although most cases of angioedema get better without treatment after a few days, medication is often used.

For cases of allergic and idiopathic angioedema, antihistamines and oral steroids (steroid tablets) can be used to relieve the swelling.

Drug-induced angioedema can usually be treated by using an alternative medication to treat whatever underlying condition you have.

Although the condition cannot be cured, regular drug treatment can prevent attacks in people with hereditary angioedema.

Read more about treating angioedema.

Published Date
2012-10-26 09:47:15Z
Last Review Date
2012-09-24 00:00:00Z
Next Review Date
2014-09-24 00:00:00Z


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The information in the Map has been approved by the UK’s leading clinical experts, is based on the best available clinical evidence, and is continually updated. To take advantage of this unique resource go to:

Map of Medicine: Urticaria and angioedema

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2012-05-28 10:58:42Z
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Symptoms of angioedema

The main sign of angioedema is swelling that develops below the surface of the skin.

Swollen skin

The swelling is caused by a collection of fluid in the deep layers of the skin.

It most often affects the hands, feet, eyes, lips, or genitals. In severe cases, the inside lining of the throat and bowel can be affected (see below).

The swelling usually appears suddenly, and is much more severe than normal hives (nettle rash). It commonly lasts one to three days. There may be a prickling sensation in the affected area before swelling is visible.

The swelling is not itchy and the skin may look a normal colour, but many people with allergic or idiopathic angioedema also develop hives, which is itchy and red.

Other symptoms

As well as visible swellings, angioedema can cause other symptoms, including:

  • a hot or painful sensation in the swollen areas
  • swelling of the inside of the throat, the windpipe and the tongue, making breathing difficult.
  • swelling of the conjunctiva (the transparent layer of cells that cover the white part of the eye), which affects vision

People with hereditary angioedema may also experience:

  • abdominal (tummy) pain caused by swelling in the stomach and bowel, which can cause nausea, vomiting and diarrhoea
  • swelling of the bladder or urethra (the tube that connects the bladder to the genitals), which can cause bladder problems and difficulty passing urine

When to seek medical advice

Contact your GP if you have an episode of angioedema that does not affect your breathing and you have not previously been diagnosed with the condition. You will need to have some tests to determine what type of angioedema you have.

When to seek emergency medical advice

Dial 999 to request an ambulance if you suspect that you, or someone you know, is experiencing anaphylaxis (a severe allergic reaction). Tell the operator that you suspect anaphylaxis.

Initial symptoms of anaphylaxis include:

  • a feeling of tightness in the chest that leads to hoarseness and wheezing
  • swelling of the tongue and throat

Left untreated, more advanced symptoms will quickly develop, such as:

  • high-pitched, rapid, shallow breathing as a result of the airways in the chest and throat becoming blocked
  • mental confusion
  • anxiety
  • agitation
  • pale blue skin (cyanosis) that feels cold and clammy to the touch
  • an increased pulse and heart rate

If you, or the person in your care, has previously been prescribed an adrenaline auto-injector pen, you should use it while waiting for the ambulance to arrive.

Published Date
2012-10-26 09:47:28Z
Last Review Date
2012-09-24 00:00:00Z
Next Review Date
2014-09-24 00:00:00Z
Abdominal pain,Angioedema


Treating angioedema

Medication is the main treatment for angioedema, although many cases getter better after a few days without treatment.

Allergic angioedema and idiopathic angioedema are usually treated in the same way, using a combination of antihistamines and corticosteroid tablets to help relieve the swelling.

Drug-induced angioedema can usually be treated by using an alternative medication to the one that is causing your symptoms.

If you have also had symptoms of anaphylaxis during an episode of angioedema, you will probably be given an adrenaline auto-injector pen in case your symptoms recur.

Read more about treating anaphylaxis.

Hereditary angioedema cannot be cured and does not respond to adrenaline, antihistamines or steroids, so a preventative approach is taken. A number of different medications are used to stabilise the protein levels in your blood to help prevent symptoms developing.

Each treatment option is discussed in more detail below.


Antihistamines work by blocking the effects of a protein called histamine, which is one of the chemicals responsible for causing swelling of your skin.

A two-week course of the newer non-sedating type of antihistamines (which do not cause drowsiness) is usually recommended – these include fexofenadine and cetirizine. Cetirizine can be bought over-the-counter in pharmacies and supermarkets without a prescription.

Antihistamine can also be given by injection at hospital or at your GP’s surgery by a nurse or your GP.

If you also have hives and are being kept awake at night by itchy skin, your GP may prescribe the older type of antihistamine to take before going to bed. The older types do cause drowsiness and should help you to sleep.

A minority of people will still experience drowsiness after taking the newer type of antihistamines. If you find yourself feeling drowsy, you should avoid:

  • driving
  • drinking alcohol
  • operating complex or heavy machinery

Other side effects of the newer antihistamines include:

  • headache
  • dry mouth
  • dry nose

These side effects are usually short-lived and should pass quickly.


Cotricosteroids (steroids) work by blocking many of the actions of your immune system. In most cases, a three to five-day course of steroid tablets is recommended. A steroid called prednisolone is the preferred choice.

Side effects of prednisolone include:

  • nausea
  • abdominal (tummy) pain
  • tiredness
  • oral thrush – a fungal infection inside your mouth
  • dizziness

If you feel dizzy after taking prednisolone, avoid driving and operating heavy machinery. These side effects should pass once you finish the course of treatment.

Steroid injections may be needed for more severe cases of angioedema. These are usually administered in hospitals or at specialist clinics by an allergy specialist or immunologist (a doctor who specialises in treating conditions that affect the immune system).

Medication for hereditary angioedema

The medication that is used to treat hereditary angioedema falls into one of two categories:

  • medication used to prevent angioedema
  • medication used to relieve symptoms

Danazol is a synthetic hormone that is effective in preventing the symptoms of angioedema because it helps boost levels of the C1-INH protein.

However, danazol can cause a number of unpleasant side effects if used on a long-term basis. For example, it may cause:

  • weight gain
  • depression
  • disruption to the menstrual cycle, such as irregular periods or absent periods
  • high blood pressure
  • in women, changes to the body that are usually associated with men, such as excessive body hair growth, flattening of the chest, deepening of the voice and an increase in muscle tone
  • liver problems

Due to these side effects, many people with hereditary angioedema are uneasy about using danazol on a long-term basis. Stanozolol is a similar medication that is slightly better tolerated.

Tranexamic acid is also an alternative medication to danazol. It can be as effective as danazol but does not cause as many side effects and is preferred for use in women.

Icatibant is a relatively new medication that is used to treat acute (short-lasting) episodes of swelling. It works by blocking the effects of some of the chemicals that are responsible for causing the swelling in cases of hereditary angioedema. Icatibant is given by injection under the skin. A second injection is often required.

Common side effects of icatibant include:

  • adverse skin reactions at the site of the injection, such as pain, redness, swelling or itchiness
  • itchiness in other areas of the skin  
  • dizziness

Purified C1-inhibitor concentrate is widely used to replace the missing protein in the blood. It is needed for patients undergoing surgery to prevent attacks caused by surgical trauma. It is used to treat acute attacks, and is injected directly into the vein.

Many patients will keep supplies of their concentrate at home for emergency use.

Icatibant and C1-inhibitor concentrate will be prescribed by the specialist immunology unit caring for the patient with hereditary angioedema.

Published Date
2012-10-26 09:48:08Z
Last Review Date
2012-09-24 00:00:00Z
Next Review Date
2014-09-24 00:00:00Z