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Urticaria and Angioedema
What are urticaria and angioedema?

Urticaria, also known as hives, is common, and affects about 20% of people (one in 5 people) at some point in their lives. Urticaria consists of pink or white raised areas of skin resembling nettle rash, known as wheals (also spelled weals), which are usually itchy. The wheals are often round or ring-shaped. Wheals can also appear as lines when the skin is firmly stroked. They can appear anywhere on the skin. Individual wheals typically disappear of their own accord within 24 hours without a trace, although the course of the condition is longer.

Angioedema is characterised by deeper swelling in the skin, which may take over 24 hours to clear. It is not usually itchy and can affect the lips and tongue. Some patients have one or the other condition, others have both.

The most common form of urticaria is called spontaneous urticaria. In this type no cause is usually identified and often patients have hives and angioedema occurring together. Spontaneous urticaria with or without angioedema is usually divided into ‘acute’ and ‘chronic’ forms. In ‘acute’ urticaria, the episode lasts up to six weeks. Chronic urticaria, by definition, lasts for more than six weeks.

Other types of urticarial rash are described later in this leaflet, including urticarial vasculitis (in which there is inflammation of the blood vessels and is therefore different from normal urticaria).

What causes urticaria and angioedema?

Urticaria is caused by the release of histamine from cells in the skin called mast cells.

Often a specific cause cannot be found. Sometimes an infection such as a cold can be a trigger. Other triggers include physical contact with an allergen such as an animal, sun exposure or a specific food or medicine. For young babies, in whom it is rare, cow’s milk allergy is the commonest trigger. Bee and wasp stings can trigger urticaria, as can eating shellfish, nuts, apples and peaches.

If you suspect that a medicine may have caused urticaria, you should inform your doctor. You or your doctor can complete a ‘yellow card’ to inform the Medicines and Healthcare Regulatory Authority (MHRA) (https://yellowcard.mhra.gov.uk/). Almost any medicine can cause urticaria, but painkillers (especially aspirin and medicines like ibuprofen), antibiotics (especially penicillins), blood products and vaccinations are most likely to be responsible. Angioedema, in particular, can be caused by a type of drug (ACE inhibitors) used to treat high blood pressure.

Some people with urticaria have conditions such as pernicious anaemia or thyroid disease, caused by the immune system directing an attack against the patient’s own tissues.

In some patients with chronic spontaneous urticaria, the release of histamine from skin mast cells is triggered by factors circulating in the blood, such as antibodies directed against their own mast cells - a process known as autoimmunity. Tests for this are not routinely available, and generally do not alter the treatments used.

Urticaria is often thought to be due to allergy, but in fact, allergy is not a common cause of urticaria.

What are the symptoms of urticaria and angioedema?

The main symptom of urticaria is itch; angioedema is not usually itchy but may be painful. Although urticaria can be distressing, because of the itching and its appearance, it has no direct effect on general health. Rarely, the swelling of angioedema may affect the tongue or throat, causing difficulty with breathing or swallowing. This can be alarming but is rarely life-threatening.

Is urticaria hereditary?

The vast majority of urticaria is not hereditary. A rare form of angioedema, (hereditary angioedema) and some very rare urticaria syndromes can run in families.

What does urticaria look like?

The wheals of urticaria may be white, pink or red. They can be of different shapes and sizes, and often look like nettle stings. Although the rash may persist for many weeks or months, individual lesions typically disappear within a day, and often last only a few hours. They occasionally leave bruising especially in children. New wheals may then appear in other areas. In spontaneous urticaria, wheals can occur anywhere on the body, at any time.

The deeper swellings of angioedema occur most frequently on the eyelids, lips and sometimes in the mouth, but they may occur anywhere. They are not usually itchy, and tend to last a few days. The skin may feel tight and painful.

How is chronic urticaria diagnosed?

Usually its appearance, or a description of it, will be enough for your doctor to make the diagnosis. In the vast majority of people no cause can be found, though your doctor will ask you questions to try to identify one. There is no special test that can reliably identify the cause of urticaria, and most people with spontaneous urticaria do not need any tests at all.

Occasionally, if a trigger is suspected, a specific blood test, to detect antibodies in the bloodstream, or a skin prick test may be performed by a Dermatologist or Allergist in skin or allergic disease. In chronic urticaria routine allergy tests are not necessary. In a small percentage of people, foods, food colouring agents and preservatives appear to worsen urticaria, and it might be helpful to identify these by keeping a food diary. These substances can be left out of the diet to see if the condition improves, and later reintroduced to confirm whether they are the cause of the urticaria. However, as urticaria is such a fluctuating disease, this is not always accurate and will not always show you definitely what is causing the problem.

Can urticaria be cured?

The treatments outlined here suppress the symptoms of the condition rather than cure it. In about half of the people affected by chronic ordinary urticaria, the rash lasts for 6-12 months, and then gradually disappears. It can however last considerably longer. In any one individual the course of urticaria is unpredictable. 

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