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A blotchy red sometimes elevated skin rash moving from site to site and changing each day.

Urticaria is an itchy condition of the skin which often appears for no apparent reason. The affected areas of skin are usually red, sometimes they are raised above the normal skin, frequently these affected areas of skin move from one area of the body to another over a period of hours and sometimes (especially on the face) the affected areas can become very swollen for a while.

Sometimes the lesions appear at sites of skin friction or scratches, even fairly minor rubbing can cause the appearance (see scratched forearm photo below). This curious type of urticaria is called dermographism. Usually the condition comes for a few days then goes away for a while although sometimes the problem is more persistent.

It is presumed that the cause of urticaria in some people is a skin reaction to 'foreign' chemicals or foreign proteins which may be introduced into the body in medications, foodstuffs, or by a variety of infections. Unfortunately there are no skin tests or blood tests which can indicate which of these possible causes may be responsible. Usually infections and medications can be excluded as a cause by your doctor. In the vast majority of patients all investigations performed are entirely normal and no detectable cause for the urticaria can be found.

To try to establish whether food/drink may be responsible for the urticaria the only practical approach is to keep a food diary, i.e. keep a written account of what has been eaten for about a month. Then go back through the month and try to establish a relationship between attacks of urticaria and particular foods/drinks taken during the previous 24 hours.

If it is possible to find a suspect food/drink then cut it out completely for a further month and see what happens. Usually it is impossible to find a responsible foodstuff unless it is very obvious right from the start. Very occasionally special exclusion diets (e.g. exclude all dairy produce) are of some help but these should only be performed with the help of a professional dietitian.

In most patients the cause of their urticaria is never discovered but as time goes by the condition gradually disappears anyway. During the period that it takes to go away many of the symptoms can be controlled by taking antihistamine tablets. These tablets are very safe and can normally be taken for prolonged periods if necessary (double check with your doctor if you might be pregnant).

They sometimes have the side effect of drowsiness and can also interact with alcohol. Patients taking antihistamines should be extra careful when operating any form of machinery (especially driving a car) and should never do so if they have also been drinking any alcohol.

Avoidance strategies can be of great benefit in some patients with urticaria, it might be a good time to consider a consultation with a Consultant Dermatologist. For my expert opinion now, use 'consult the specialist' here.

by Dr John Ashworth

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