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:
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.
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 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.
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:
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 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:
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.
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.
Symptoms of angioedema
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.
As well as visible swellings, angioedema can cause some or all of the following symptoms:
People with hereditary angioedema may also experience:
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:
Left untreated, more advanced symptoms will quickly develop, such as:
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
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:
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:
Avoiding these triggers whenever possible may improve your symptoms.
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:
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.
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.
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:
See the Health A-Z topic about Allergies - diagnosis for more information.
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 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 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 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:
Other side effects of the newer antihistamines include:
These side effects are usually short-lasting 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 usually recommended. A steroid called prednisolone is the preferred choice.
Side effects of prednisolone include:
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:
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:
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:
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.
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Map of Medicine: Urticaria and angioedema