Angioedema is swelling of the deeper layers of the skin. The swelling is often severe and is caused by a build-up of fluid. The symptoms of angioedema can affect any part of the body, but they usually affect the:

• eyes
• lips
• genitals
• hands
• feet

Medication, such as antihistamines and oral steroids (steroid tablets), can be used to relieve the swelling. In particularly troublesome cases they can also prevent symptoms from occurring in the first place.

See Angioedema - treatment for more information.

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

See the Health A-Z topic about Urticaria for more information about the condition.

Types of angioedema

There are four main types of angioedema:

• allergic angioedema - the swelling is caused by an allergic reaction, such as a reaction to peanuts
• 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
• hereditary angioedema - the swelling is caused by 'faulty' genes that are inherited from a person's parents; unlike the other types of angioedema, people with hereditary angioedema do not experience urticaria

Allergic angioedema

Allergic angioedema is thought to be the most common type of angioedema. It often affects people with food allergies. Food allergies are thought to affect 5-8% of children and 1-2% of adults.

Very severe allergic reactions can cause swelling of the throat, which can cause breathing difficulties and a sudden fall in blood pressure. This type of extreme allergic reaction is known as anaphylaxis and is a medical emergency.

In most cases, allergic angioedema is an acute (short-lived) condition because after a person has identified the substance (allergen) responsible for triggering the allergic reaction, they can avoid it in the future.

Idiopathic angioedema

It is difficult to estimate how common acute idiopathic angioedema is because many cases may be misdiagnosed as allergic angioedema.

However, chronic (long-lasting) idiopathic angioedema is uncommon. It is estimated to affect around 1 in 2,000 people. People with chronic idiopathic angioedema may also experience symptoms of urticaria.

Stress is the most common cause of idiopathic angioedema, but it can also be caused by:

• thyroid gland problems
• a deficiency of iron, vitamin B12 or folic acid
• infections, particularly dental, sinus and gallbladder infections.

Drug-induced angioedema

Drug-induced angioedema is an uncommon side effect of certain medications. Symptoms of angioedema can be triggered by a type of medication known as angiotensin-converting enzyme (ACE) inhibitors, which are used to treat high blood pressure (hypertension). This can come on at any time after the medication is started. It can last for up to three months after the medication has stopped.

Drug-induced angioedema is not the same as having an allergic reaction to certain medications, such as penicillin. This is because the underlying mechanisms are very different. It is often days and, in many cases, years before you notice a reaction, but an allergic reaction develops within a few minutes to an hour.

It is estimated that 1 in 500 people who are being treated with ACE inhibitors will develop angioedema.

Hereditary angioedema

Hereditary angioedema is the rarest type of angioedema, estimated to affect 1 in 25,000 people.

Hereditary angioedema is caused by the lack of a protein in the blood called C1-esterase inhibitor. Unlike allergic angioedema, the swellings tend to come on slowly. It can affect the throat and the bowel, and cause abdominal (tummy) pain.

Hereditary angioedema attacks tend to begin after puberty, and they can occur with any frequency. They can be triggered by:

• trauma or infection
• the oral contraceptive pill
• pregnancy

Specific medication is available to prevent and treat attacks of hereditary angioedema.

How common is angioedema?

It is estimated that 10-20% of people are affected by angioedema at some point during their life.

Outlook

The outlook for allergic angioedema is generally good. The symptoms usually pass within one to three days. However, the condition can be unpredictable. A recurrence of symptoms is common.

The outlook for idiopathic angioedema is mixed. While the symptoms do not usually pose a serious risk to health, the frequent reoccurrence of symptoms can be frustrating and unpleasant to live with.

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

The outlook for hereditary angioedema is generally good because a number of different medications can successfully prevent the onset of symptoms.

Swollen skin

The main sign of angioedema is swelling that develops below the surface of the skin. The swelling is caused by a collection of fluid in the deep layers of the skin.

The swelling 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 often appears suddenly, and is much more severe than normal hives (nettle rash). It usually lasts one to three days.

The swelling is not itchy, but many people with allergic or idiopathic angioedema also develop urticaria (a raised skin rash), which is itchy.

Other symptoms

As well as visible swellings, angioedema can cause some or all of the following symptoms:

• a burning hot or painful feeling in the swollen areas
• swelling of the inside of the throat, the air tubes in the lungs 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 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 this.

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.

Allergic

An allergen is a substance that reacts with the body's immune system and causes an allergic reaction.

Diarrhoea

Diarrhoea is the passing of frequent watery stools when you go to the toilet.

Nausea

Nausea is when you feel like you are going to be sick.

Stomach

The sac-like organ of the digestive system. It helps digest food by churning it and mixing it with acids to break it down into smaller pieces.

Allergic angioedema

Allergic angioedema is caused by the immune system. The immune system protects your body from illness and infection by producing specialised cells called antibodies. Antibodies identify potential threats, such as bacteria and viruses. They send signals to your immune system to release chemicals to destroy the threat and prevent the infection from spreading.

However, in the case of allergic angioedema, your immune system mistakes harmless proteins that are found in certain substances as a threat to your body. Your immune system responds by releasing chemicals such as histamines. They cause the blood vessels to expand, which leads to swelling of the skin.

Substances known to trigger allergic angioedema include:

• certain types of food - in particular, nuts, shellfish, milk and eggs
• some types of medication, such as penicillin, aspirin and non-steroidal anti-inflammatory drug (NSAID) painkillers, such as ibuprofen
• insect bites and stings - in particular, wasp and bee stings
• latex - a naturally occurring rubber that is used to make medical gloves, balloons and condoms

Idiopathic angioedema

Idiopathic is a Greek word that describes a condition of unknown origin. The exact cause of idiopathic angioedema is unknown. However, it appears that some sort of problem with the immune system causes it to 'misfire' at certain times.

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

• stress
• alcohol
• caffeine
• spicy food
• overheating
• wearing tight clothes

Avoiding these triggers whenever possible may improve your symptoms.

Drug-induced angioedema

The leading cause of drug-induced angioedema is a type of medication called angiotensin-converting enzyme (ACE) inhibitors, which are used to treat high blood pressure (hypertension).

It is estimated that 0.1% to 2.2% 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 occur 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:

• bupropion - a medication that helps people to give up smoking
• vaccines
• selective serotonin reuptake inhibitors (SSRIs; a type of antidepressant)
• COX-II inhibitors - a type of painkiller that is used to treat chronic pain conditions, such as arthritis
• non-steroidal anti-inflammatory drugs (NSAIDs; a type of painkiller)
• angiotensin-2 receptor antagonist - another medication that is used in the treatment of high blood pressure
• statins - used to treat people with high cholesterol levels
• proton pump inhibitors (PPIs) - used to treat stomach ulcers

Hereditary angioedema

Hereditary angioedema is caused by a genetic mutation in a gene known as C1-1NH. Genes are single units of genetic material which contain information that determine characteristics such as eye and hair colour.

Genetic mutations occur when a molecule inside the gene called deoxyribonucleic acid (DNA) changes, altering the genetic instructions.

As a result of the mutated C1-1NH gene, the body does not make enough C1-1NH protein. This protein plays an important role in regulating the immune system (the body's natural defence against infection and illness). Without enough C1-1NH protein, the immune system can misfire and trigger the symptoms of angioedema.

The mutated C1-1NH 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.

Blood vessels

Blood vessels are the tubes in which blood travels to and from parts of the body. The three main types of blood vessels are veins, arteries and capillaries.

Deficiency

If you have a deficiency it means you are lacking in a particular substance needed by the body.

Immune system

The immune system is the body's defence system, which helps protect it from disease, bacteria and viruses.

Swellings

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Confirming a diagnosis of angioedema is relatively straightforward. Your GP physically examines the affected area of skin and asks you about any associated symptoms, such as swelling of your throat or abdominal (tummy) pain.

Further testing will be needed to confirm what type of angioedema you have, as this will determine the type of treatment you receive.

Allergic angioedema

Your GP will ask whether you have recently been exposed to an allergen (an allergy-causing substance), such as nuts or latex, and whether you have a history of other allergic conditions, such as urticaria or asthma. People who have one allergic condition often go on to 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:

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

See the Health A-Z topic about Allergies - diagnosis for more information.

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 no longer 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 levels of the proteins that are regulated by C1-1NH (Complement C4). If this is low, the levels of C1-1NH protein in your blood and its function can be measured. Very low levels would suggest a diagnosis 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 of the tests described above have been carried out, and a cause has not been found.  

Allergic angioedema and idiopathic angioedema are usually treated in the same way.

Antihistamines and corticosteroid tablets can be used to help relieve the symptoms of swelling. In more severe cases where the swelling persists for several days, steroid injections can be used.

Another important factor in successfully treating allergic angioedema is to avoid exposure to the allergen that is responsible for your symptoms.

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

Hereditary angioedema does not respond to adrenaline, antihistamines or steroids, so a preventative approach is taken, i.e. a number of different medications are used to stabilise the protein levels in your blood. This should help prevent the symptoms from developing.

If you have also had symptoms of anaphylaxis during an episode of angioedema, you are likely to also be given an adrenaline auto-injector pen in case your symptoms recur. See Anaphylaxis - treatment for more information.

Each treatment option is discussed in more detail below.

Antihistamines

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 type of antihistamines tablets, which were developed during the 1990s, that do not cause drowsiness (non-sedating antihistamines) is usually recommended, such as fexofenadine and cetirizine. Cetirizine can be bought over the counter in pharmacies and supermarkets without a prescription.

Antihistamine can be given by injection, at hospital, or at your local GP's surgery by a nurse or your GP.

If you also have symptoms of urticaria and itchy skin is keeping you awake at night, your GP may also prescribe the older type of antidepressant (that were developed shortly after World War 2) to take before going to bed. These 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-lasting and should pass quickly.

Corticosteroids

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 usually recommended. A steroid called prednisolone is the preferred choice.

Side effects of prednisolone include:

• indigestion
• nausea (feeling sick)
• abdominal (tummy) pain
• increased appetite
• tiredness
• oral thrush - fungal infection inside your mouth
• dizziness

Again, 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 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 - this is known as prophylaxis
• medication used to relieve symptoms when they occur

Danazol is a synthetic hormone that is effective in preventing the symptoms of angioedema because it helps boost levels of the C1-1NH 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 (hypertension)
• in women, changes to the body that you would usually associate with men, such as body hair, flattening of the chest, deepening of the voice and an increase in muscle tone
• liver problems

As a result of 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 an alternative medication to danazol. It is usually 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
• headache
• dizziness
• skin rash

Purified C1-inhibitor concentrate (plasma-derived or recombinant) is still 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, which they can take to the nearest accident and emergency (A&E) department. Icatibant and C1- inhibitor concentrate will be prescribed by the specialist immunology unit caring for the patient with hereditary angioedema.

Adrenaline

Adrenaline is a hormone produced at times of stress that affects heart rate, blood circulation and other functions of the body.

Allergic

An allergen is a substance that reacts with the body's immune system and causes an allergic reaction.

Anaphylactic shock.

Anaphylactic shock is a severe and sometimes life-threatening allergic reaction, causing swelling of body tissues and a drop in blood pressure. 

Antihistamines

Antihistamine medicine counteracts the action of histamine (a chemical released during an allergic reaction). For example loratadine, hydroxyzine.

Blood

Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.

Corticosteroid

Corticosteroid is a naturally occurring hormone produced by the adrenal gland, or a synthetic hormone having similar properties. It is used to reduce inflammation, so reducing swelling and pain.

Genetic

Genetic is a term that refers to genes- the characteristics inherited from a family member.

Lungs

Lungs are a pair of organs in the chest that control breathing. They remove carbon dioxide from the blood and replace it with oxygen. 

Oxygen

Oxygen is an odourless, colourless gas that makes up about 20% of the air we breathe.

Plasma

Plasma is the liquid part of blood, which holds other blood cells together.

Swelling

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

The Map of Medicine is used by doctors throughout the NHS to determine the best treatment options for their patients. NHS Choices offers everyone in England exclusive and free access to this cutting-edge internet resource, which lets you see exactly what your doctor sees.

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