About angioedema

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 experience urticaria (hives). This is a raised, red and itchy rash that appears on the skin.

man with swollen bottom lip
Angioedema can cause swelling in any part of the body, including the lips. Source: https://dermnetnz.org/
man with right eye that is swollen shut
Angioedema can cause swelling around the eye. Source: https://dermnetnz.org/

Why does angioedema happen?

The cause of angioedema depends on the type you have. There are 4 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 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.

Who is affected

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

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


Your doctor can diagnose angioedema by examining the affected skin and discussing symptoms.

However, further tests, such as blood tests or allergy tests, may be required to determine the type of angioedema.

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

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.

Symptoms of angioedema

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

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 more severe than normal hives (nettle rash). It commonly lasts 1 to 3 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; however, many people with allergic or idiopathic angioedema also develop urticaria (hives), which is red and itchy.

pair of hands with swelling in the right one
Swelling caused by angioedema often affects the hands and feet. Source: https://dermnetnz.org/

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 (stomach) 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 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 breathing problems 
  • swelling of the tongue and throat

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.

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 attacking germs in your body.

In allergic angioedema, your immune system mistakenly attacks 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".

In cases of idiopathic angioedema, certain triggers may lead to swelling, such as:

  • anxiety or stress
  • minor infections
  • hot or cold temperatures
  • exercise

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's estimated that around 1-5% of people taking ACE inhibitors will develop drug-induced angioedema. Black people being treated with ACE inhibitors are 3 to 4 times more likely to develop this side effect than white people.

Around 1 in 4 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 things are thought to trigger hereditary angioedema, such as:

The mutated C1-inh gene is passed down through families. If you have hereditary angioedema, you have a 50% chance of passing it on to your children.

Diagnosing angioedema

Angioedema is usually diagnosed by your doctor examining the affected skin and discussing your symptoms.

It can be difficult to find the exact cause and identify which type of angioedema you have. There is no single test available, but you may have allergy tests or blood tests if a specific cause is suspected.

Allergic angioedema

You're likely to be asked if you have recently been exposed to any allergy-causing substances, such as nuts or latex. You may also be asked whether you have a history of other allergic conditions, such as urticaria (hives) or asthma. People with an allergic condition often develop other allergic conditions.

Tell your doctor about any medications you are taking, including over-the-counter medication, such as painkillers, herbal supplements and vitamins.

Your GP may recommend that you keep a diary of your exposure to possible irritants – or a food diary, if a food allergy is suspected.

If 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
  • 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 known to cause drug-induced angioedema, your GP will withdraw that medication and prescribe an alternative. You should not stop taking any prescribed medication without advice from a health professional.

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 using a blood test to check the level of proteins regulated by the C1-inh gene. A very low level would suggest 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 "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 an iron deficiency, liver diseases and problems with the thyroid gland – your doctor or specialist will undertake some simple blood tests to check for these conditions.

Treating angioedema

Medication is the main treatment for angioedema, although many cases get 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 corticosteroids to help relieve the swelling.

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

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

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.


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

A 2-week course of a non-sedating type of antihistamine (which does 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.

Antihistamines can also be given by injection at hospital or your GP surgery.

If you also have urticaria (hives) and are being kept awake at night by itchy skin, your GP may prescribe an older type of antihistamine to take before going to bed. These types cause drowsiness and should help you 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.


Corticosteroids (steroids) work by blocking many of your immune system's actions. In most cases, a 3 to 5 day course of steroid tablets is recommended. A steroid called prednisolone is the preferred choice.

Side effects of prednisolone include:

  • nausea
  • abdominal (stomach) 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 used to treat hereditary angioedema falls into 1 of 2 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

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 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, and 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's needed for patients undergoing surgery, to prevent attacks caused by surgical trauma. It's 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.

Last updated:
29 May 2023