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Urticaria and Angioedema

Urticaria is also known as 'nettle rash' or 'hives'. The condition consists of wheals - spots or patches of raised red or white skin - each of which usually clear away in a few hours, and are then replaced by other fresh wheals. The wheals are usually itchy, painful or cause a burning sensation. It sometimes occurs together with swelling of various parts of the body (angioedema) - typically the face, hands and feet, although anywhere may be affected.

Urticaria is very common and affects one in five people at some point in their lives. In most people, it settles quickly and is no more than a mild inconvenience, but it can be severe, long-lasting and troublesome in some cases.

Mild transient (acute) urticaria may occur in some people due to infection, medications or after excessive exposure to sunlight or UV light. Urticaria is defined as chronic if it lasts more than 6 weeks.

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

In acute urticaria (approx. 20 per cent of urticaria cases) the cause is true allergy to a food, drug or other substance that the person has eaten or been in contact with (plants, animals etc.). Recurrent attacks, each lasting for only a few hours, especially if seasonal, are more likely to be allergy-related. They often occur in people who have other allergy symptoms (asthma, hay fever, food allergy etc.). Physical urticaria is a response to physical factors such as pressure, heat and cold. This type of urticaria clears within thirty minutes to one hour and people suffering from it have usually identified the cause before visiting their doctor.

The more common type of urticaria rash lasts up to 24 hours, produces larger wheals and may not completely clear for several days. Urticaria is often found under tight clothing, and there may occasionally be associated swelling of the lips and eyelids (angioedema). Attacks which are recurrent may continue for weeks on end, or be interlaced with lengthy periods with no symptoms. There are a variety of possible causes of this type of urticaria and in most people a cause is never identified.

It is not possible to identify an underlying allergy in the remaining 80% of patients who have chronic urticaria. Allergy blood tests and skin tests are usually negative. In these patients, the urticaria may arise in a number of other ways:

  1. Associated with physical influences such as heat, cold, pressure, exercise, etc.
  2. Due to certain drugs such as aspirin, codeine and related painkillers, ibuprofen or other non-Steroidal anti-inflammatories, blood-pressure drugs or statins
  3. Associated with eating certain chemicals added to foods (e.g. colourings and preservatives)
  4. Rarely, as part of a disorder called urticarial vasculitis, erythema multiformae or other generalised illnesses. For more information see the British Association of Dermatologists: http://www.bad.org.uk/shared/get-file.ashx?id=184&itemtype=document
  5. In some people, foods may trigger urticaria through some other 'non-allergic' mechanism (non-allergic hypersensitivity, or food intolerance). Foods containing high levels of particular naturally-occurring substances such as salicylates or histamine are implicated in some people
  6. Stevens Johnson Syndrome is a part of a spectrum of skin conditions when there raised red rings and often blisters. In Stevens Johnson syndrome, there are also blisters in the mouth. It usually occurs after a viral infection but occasionally as a drug reaction. For more information see: http://www.gosh.nhs.uk/medical-information/search-medical-conditions/stevens-johnson-syndrome

Angioedema is the name given to deeper swelling affecting the skin over the arms, legs, torso or face. It may also affect the tongue, mouth, throat and sometimes the upper airway. These swellings commonly last for more than 24hrs, and usually there is no itching. It is not possible to identify an underlying cause for angioedema in the vast majority of cases. Some drugs (including some used to treat high blood pressure) can cause angioedema, and there is also a rare inherited form which does not respond to antihistamines.

Urticaria and angioedema often occur at different times or together in the same person. They occur in about 15 per cent of the population at some time or other in their lives, women being affected more commonly than men. Urticaria occurs alone in about 40 per cent of cases, angioedema in about 10 per cent and they co-exist in the same individual (not necessarily at the same time) in about 50 per cent of cases.

Investigations for urticaria

Investigations are usually unhelpful. The total amount of IgE antibodies can be raised in blood, but is usually normal, and skin prick tests usually give negative results. There are no good laboratory investigations available. Some specialist centres offer elimination diets and challenges with suspected foods, chemicals or drugs, but these are not widely available.

Investigations normally centre on excluding other diseases and conditions which are sometimes related to urticaria, such as thyroid dysfunction. 

Treatment of urticaria

There are two important aspects of treatment for urticaria: avoidance of any reasonably suspected trigger, and treatment with drugs.

Individuals who have urticaria due to aspirin may need to avoid foods that contain high levels of salicylates (see 'Aspirin/salicylates factsheet). Advice regarding a low salicylate (pseudo-allergen) diet from a dietician may benefit those who are very sensitive to salicylates. Avoidance of certain food additives may also require detailed information. A good information leaflet on food additives is available from the Food Standards Agency.

Antihistamines are the mainstay of drug treatment for urticaria and angioedema. They may be taken just when required (at the onset of an episode of urticaria, when many of them will begin to have an effect within 30-60 minutes) or regularly to prevent episodes occurring in chronic spontaneous urticaria. Several of the older antihistamines are very effective, but produce excessive tiredness and drowsiness in many patients. This occurs less often with the newer antihistamines. Some people find that one antihistamine works better than another, so that if the first one fails to control symptoms, it may well be worth trying others. Specialists sometimes prescribe higher-than-usual doses, but this should only be done under supervision.

Other prescription drugs are used to treat urticaria and angioedema if ordinary antihistamines do not control the symptoms effectively. Drugs to supress or modulate the immune system have been used but may require monitoring with blood tests.  A new licensed drug, ‘Omalizumab’ now exists as an anti-IgE biologic, given as a monthly injection. It has been proven to be extremely helpful in cases of chronic spontaneous urticaria unresponsive to antihistamines.

Chronic spontaneous urticaria often 'burns itself out' after a period of time, and the symptoms do eventually disappear. Treatment is directed at symptom control until the urticaria settles spontaneously.

 

Last updated: November 2015                   Next review date: November 2018
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