What is urticaria?
Urticaria is a very itchy skin rash which comes and goes. It affects the most superficial layers of the skin and appears as multiple itchy lumps which are often red or white in colour and are surrounded by a blotchy red area. Individual lumps last a few hours and then subside, but they may spread across the body and can be replaced by new areas of urticaria. Sometimes a similar reaction affects the tongue and mouth and this is termed angioedema.
Urticaria may occur for a short period and is usually called acute urticaria if the condition lasts for less than six weeks altogether. When it lasts longer it is called chronic urticaria. The causes of acute urticaria are different from those of chronic urticaria. In both types, the immediate cause of the rash is the release into the skin of a natural substance called histamine. Histamine is formed in cells called mast cells which are found throughout the body especially at the surfaces of the eyes, nose, lungs and skin. Histamine is also made by stinging nettles and this is why the rash seen in urticaria looks like stinging nettle reaction.

What can cause urticaria?
Many different triggers can cause the release of histamine from mast cells. Allergy to foods and insect venom is one of the triggers but is not by any means the commonest. In acute urticaria the commonest cause is a viral infection which destabilises the mast cells and makes them fragile so that the histamine is released easily. In chronic urticaria the cells may release histamine to physical stimuli such as heat, cold, vibration or scratching. Some patients have antibodies directed against the surface of the mast cell. These antibodies trigger the release of histamine and may persist for many months. A few people do not have enough of some proteins called complement which switch off the immune systems: this condition can run in families and is fairly easy to diagnose with blood tests. Urticaria and angioedema are sometimes associated with other conditions including thyroid disease and immune system problems. A number of drugs including aspirin and other painkillers can cause urticaria and can also make make urticaria worse when it is caused by something else. Alcohol and spicy food are well recognised triggers as well.

What can be done to help?
The management of urticaria and angioedema depends partly on the pattern and duration of symptoms. Patients with acute urticaria may not need any investigation at all provided that there is no evidence that their condition is caused by allergy to food or drugs. The first step in understanding chronic urticaria is to take a careful history and sort out which trigger factors are important in each individual patient. We will then usually look for evidence of an allergy and we will try to exclude any of the immune system or glandular problems which are sometimes associated with urticaria/angioedema. If we find any of these conditions they will need treating on their own merits. If we do not find a specific cause for the rash we would normally try to suppress it with drug therapy knowing that this condition usually only last for a few months and will go away on its own. Some patients are unlucky and have a rash which lasts for 18 months or 2 years but it does usually get better in its own good time.
The mainstay of treatment is long-acting antihistamine tablets. Older antihistamines tended to send people to sleep but the newer ones (ceritizine, loratadine, fexofenadine) are very safe and effective and do not cause sedation to any appreciable extent. A few patients find they prefer one tablet to another, and it is certainly worth trying a different antihistamine if the first one does not suit you. In general, antihistamines work better when they are taken regularly rather than when people wait for the rash to occur before taking the tablets. However, if your symptoms only occur very occasionally, you may prefer to reserve the tablets for the days when you have a problem. A few patients find that antihistamines are not enough to control their urticaria. This may mean that other allergic mechanisms are involved (as well as histamine), and we will therefore try some additional drugs as well as the antihistamines. These may include another type of antihistamine (ranitidine, cimetidine, etc.), long-acting adrenaline-like substances (eg: bambuterol), tranexamic acid which is particularly useful in angioedema, or anabolic steroids (danazol or stanozolol). The choice of medication will usually be based on the severity of the symptoms and a careful consideration of the risks and benfits of additional therapy. Please do not hesitate to ask your doctor if you have any doubts about the drugs that you have been prescribed. For patients who get marked swelling of the tongue and throat, it may be suggested that you have an adrenaline syringe (Anapen or Epipen). Adrenaline is very useful in controlling inflammation in and around the throat. The Anapen/Epipen devices are very easy to use but are not required for urticaria alone. You should make sure that you understand how to use the syringe and when to use it. If in doubt ask a nurse, doctor or pharmacist to go through the procedure with you.

For further information and advice contact:

British Allergy Foundation 
Deepdene House 
30 Bellgrove Road 
WELLING, Kent DA16 3BY 
Tel: 020 8303 8792 

Anaphylaxis Campaign
PO Box 149
FLEET
Hants GU13 9XU
Tel: 01252 318723