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

Swollen skin

Credit:

DR P. MARAZZI/SCIENCE PHOTO LIBRARY

Swelling caused by angioedema can develop suddenly or come on gradually over a few hours. It normally lasts a few days.

The swelling most often affects the:

• hands
• feet
• area around the eyes
• lips and tongue
• genitals

In severe cases, the inside of the throat or bowel can be affected.

Rash

Often, the swelling occurs with a raised, itchy rash called urticaria (hives).

The rash will usually settle in a few days.

Otherwise, the skin over the swelling may feel tight and painful but look normal.

Other symptoms

Less common symptoms of angioedema include:

• difficulty breathing
• red, irritated eyes (conjunctivitis)
• tummy (abdominal) pain
• feeling sick
• diarrhoea
• dizziness
• fainting

When to get medical advice

See your GP if you have episodes of swelling that affect your skin or lips and you're not certain of the cause.

You may need to have some tests to determine the cause. Read more about tests for angioedema.

Dial 999 for an ambulance if you, or someone with you, has swelling and:

• sudden or worsening breathing problems
• feels faint or dizzy
• passes out or collapses 

These are signs of a serious allergic reaction (anaphylaxis). If you, or the person who's ill, have been prescribed an adrenaline auto-injector for this, use it while waiting for the ambulance to arrive.

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:

• certain types of food – particularly nuts, shellfish, milk and eggs
• some types of medicine – including some antibiotics, aspirin and non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen
• insect bites and stings – particularly wasp and bee stings
• latex – a type of rubber used to make medical gloves, balloons and condoms

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:

• 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, olmesartan and valsartan – another medicine used to treat high blood pressure

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:

• an injury or infection
• surgery and dental treatment
• stress
• pregnancy
• certain medicines, 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 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:

• 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.

If you have experienced angioedema for the first time, your doctor will try to work out what may have caused it.

There are several different causes of angioedema. It's important to know what's causing your symptoms, as this affects the treatment you'll need.

There's no single test to determine the cause of angioedema. Some of the checks and tests you may have are outlined in this section.

Symptoms and medical history

Your doctor may be able to get a good idea of the cause of your angioedema by asking about your symptoms and medical history.

For example:

• it's likely to have been caused by an allergy if you were exposed to something that can trigger allergic reactions (an allergen) soon before it started, or if you also developed a raised, itchy rash (urticaria or hives)
• it may have been triggered by a medicine if you're currently taking a medicine that's associated with angioedema, such as angiotensin-converting enzyme (ACE) inhibitors for high blood pressure
• it's possible your symptoms are a result of an inherited genetic fault if you have a family history of angioedema

Sometimes the tests below may be needed to confirm the cause.

Allergy tests

If your doctor thinks your symptoms may have been caused by an allergy, they may refer you to a specialist allergy or immunology clinic for further testing.

Tests you may have include:

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

These tests can help determine what you're allergic to. Read more about allergy testing.

Blood test

If your doctor thinks your symptoms may be caused by a genetic fault you've inherited from your parents, they may refer you for a blood test.

The test checks the level of a substance called C1 esterase inhibitor in your blood. This substance is important in regulating the immune system.

A very low level of C1 esterase inhibitor would suggest you have an inherited problem affecting how much of this substance your body is able to produce.

The treatment for angioedema depends on what's causing it.

There are several different types of angioedema, each of which has a different cause.

Angioedema can usually be treated at home, although severe cases may need to be treated in hospital.

Allergic and idiopathic angioedema

Allergic angioedema and idiopathic angioedema are usually treated in a similar way.

Avoiding triggers

Avoiding particular substances or activities that trigger your symptoms may help reduce your chances of experiencing swelling.

For example, if you're allergic to a certain type of food, it can help to check the ingredients in food you buy and be careful when eating out.

Read about preventing allergic reactions for more advice.

Antihistamines and steroid medicine

Your GP may suggest taking antihistamines to reduce swelling when it occurs.

Antihistamines work by blocking the effects of histamine, one of the chemicals responsible for the swelling. Some types can be bought in pharmacies and supermarkets without a prescription.

Some antihistamines can make you feel drowsy. Avoid driving, drinking alcohol or operating dangerous machinery if you experience this. If your symptoms of swelling occur during the day, it's best to take non-drowsy medicines such as cetirizine and loratadine.

Other side effects of antihistamines can include:

• headaches
• a dry mouth
• a dry nose

If the swelling is severe, your GP may prescribe a short course of steroid medicine. This is a powerful medicine that's only used for short periods because it can have troublesome side effects.

Adrenaline auto-injectors

If you have a particularly serious allergy, you may be given adrenaline auto-injectors to use if you experience a severe allergic reaction (anaphylaxis).

There are several types of auto-injector, which are used in slightly different ways.

Read about preventing anaphylaxis for more information.

Drug-induced angioedema

If a certain medicine you're taking is thought to be responsible for your angioedema, your doctor will usually advise stopping it.

They can prescribe a different medicine for you to take instead.

This is usually all that needs to be done. Tell your doctor if your symptoms continue or come back after switching medicine.

Hereditary angioedema

Hereditary angioedema cannot be cured, but medicines can help prevent and treat the swelling.

Preventing swelling

Medicines called danazol and oxandrolone can help reduce the chances of swelling occurring if you have hereditary angioedema.

These medicines boost the levels of C1 esterase inhibitor in your blood. Low levels of this substance are what causes the swelling.

Side effects of these medicines can include:

• weight gain
• in women, excessive body or facial hair growth, deepening of the voice, irregular periods or absent periods
• depression
• high blood pressure
• liver problems

A medicine called tranexamic acid may sometimes be used as an alternative, particularly in children and women. This causes fewer side effects, but may not be as effective in preventing swelling.

Treating swelling

The 2 main treatments used to treat swelling caused by hereditary angioedema are:

• icatibant – a medicine given by injection that blocks the effects of some of the chemicals responsible for the swelling
• C1 esterase inhibitor replacement – a treatment given by injection that boosts the levels of C1 esterase inhibitor in your blood

Occasionally, C1 esterase inhibitor replacement may also be used shortly before surgery or dental treatment, as it can reduce the risk of these triggering swelling.

You may be given a supply of medicine to keep at home and be taught how to give the injections yourself.