Urticaria and angioedema

Urticaria is caused by the release of histamine and other chemicals from cells in the skin called mast cells. Urticaria is often thought of as an allergy but, in fact, it usually results from histamine release from mast cells due to other reasons.

Allergens in food, or medicine may sometimes cause acute urticaria. For young babies, in whom urticaria is rare, cow’s milk allergy is the commonest cause. As children grow up, they may react to different foods, including nuts, fruits or shellfish if they become allergic. Bee and wasp stings can cause acute urticaria.

However, a specific reason for urticaria is often not found. Chronic spontaneous urticaria may be autoimmune, the patient’s own antibodies that release histamine from mast cells. Tests for autoimmune urticaria are not routinely available and generally do not alter treatment. When a cause cannot be found, it is called ‘idiopathic’. Weals may be set off by a physical trigger, such as cold, pressure or friction. This type of urticaria is called inducible because hives are induced by a specific stimulus and are not spontaneous.

Some people with urticaria have other conditions, such as thyroid disease or other autoimmune disorders.

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). Almost any medicine can cause urticaria, but painkillers such as aspirin,  ibuprofen and codeine, some antibiotics, blood products such as blood transfusions and vaccinations are most likely to be responsible. Angio-oedema without weals may be caused by a group of drugs called ACE inhibitors used to treat high blood pressure.

Is urticaria hereditary?

The vast majority of urticarias are not hereditary. Hereditary angio-oedema runs in families.

The main symptom of urticaria is itch; angio-oedema is not usually itchy but may be painful. Although urticaria may be very distressing because of the itching and its appearance, it generally has no direct effect on general health. However, it can cause a high impact on quality of life, including mood, and lead to problems with work and relationships. Rarely, angio-oedema may affect the tongue or throat. This can be alarming but is only life-threatening when angio-oedema is due to hereditary angio-oedema or ACE inhibitor medication.

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Usually its appearance, or a description of it, will be enough for your doctor to make the diagnosis. There is no special test that can reliably identify the cause of urticaria, and most people with spontaneous urticaria who respond well to antihistamines do not need any tests at all. Routine allergy tests are not necessary.

In a small percentage of people, foods, food colouring agents and preservatives appear to worsen urticaria, and it is occasionally possible 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 or not. However, as urticaria is such a fluctuating disease, this is not always accurate and will not always show what is causing the problem.

Can urticaria be cured?

The aim of treatment is to suppress the symptoms of the condition until it becomes better naturally rather than cure it. In about half of the people affected by chronic spontaneous 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.

What is the treatment of urticaria?

• Do not take aspirin, ibuprofen (and other non-steroidal anti-inflammatory drugs) or opiates, such as codeine unless it is essential, since these medicines may aggravate urticaria.
• Avoid anything that may worsen urticaria, such as heat, tight clothes, and alcohol. Triggers vary between individuals.
• Avoidance of specific foods, colouring agents and preservatives may be helpful.
• Seek medical advice urgently if you are having problems with breathing or swallowing.

In some patients, clear trigger factors for urticaria can be identified although the cause remains unknown; these are called inducible urticarias.  There are several types of inducible urticaria.

Inducible urticarias: weals may be triggered by heat, cold, friction, pressure on the skin and even by water. The weals usually occur within minutes, and last for less than one hour (except delayed pressure urticaria, which is delayed in onset and lasts for hours at least). Physical urticarias often occur in otherwise healthy young adults but can affect any age. Some patients suffer from more than one type of urticaria; they include the following types:

Other illness presenting with urticarial rash or swelling