Urticaria

Published by Bupa's Health Information Team, October 2010.

This factsheet is for people who have urticaria, or who would like information about it.

Urticaria is a skin condition that causes red, itchy swellings called weals or hives to appear on the skin. The weals usually go away within a couple of hours and aren't serious.

About urticaria

In urticaria, a chemical called histamine is released from the cells in your skin. Histamine causes fluid from blood vessels underneath the surface of your skin to leak out. This causes red, raised patches (weals) on the surface of your skin which look like nettle rash. Histamine also causes the weals to itch.

Types of urticaria

Idiopathic urticaria
Idiopathic urticaria is also referred to as ordinary urticaria. If you have idiopathic urticaria, the weals usually appear suddenly, often for no apparent reason. The weals can appear anywhere on your body. The individual weals go away within 24 hours, but new ones may appear in different areas during or after this time.

Idiopathic urticaria can be acute or chronic. The terms acute and chronic refer to how long you have had a condition, not how serious it is.

• In acute urticaria, the swellings are a one-off episode, which usually lasts for a few days or weeks. This type of urticaria is very common, affecting one in six people at some point in their lives.
• In chronic urticaria, the problem persists for longer than six weeks, with symptoms often coming and going. Chronic urticaria affects around one in every 1000 people. It goes away within six to 12 months in about half the people who have it.

Other types of urticaria
The following types of urticaria usually have a specific cause.

• Physical urticaria - this is when you repeatedly develop urticaria in response to the same physical trigger factor, such as pressure on your skin, an increase in your body temperature (for example, after exercise), cold temperature, sunlight or water.
• Contact urticaria - this follows contact with a particular substance (for example, certain chemicals, cosmetics, foods, plants, rubber or animals).
• Urticarial vasculitis - this is a rare type of urticaria caused by inflammation of your blood vessels.

You may have more than one type of urticaria at the same time.

Symptoms of urticaria

Urticaria doesn't usually make you feel unwell. The only symptoms are the weals on your skin which:

• may be red, pink or white and are often surrounded by red skin
• are usually itchy
• eventually flatten, leaving red marks that go away within 24 hours
• may come back in the same place or on a different patch of skin, hours or days after they have gone away

Causes of urticaria

Urticaria happens when histamine is released by the cells in your skin. This may have a specific trigger.

• Acute urticaria can follow a cold, flu or sore throat. Allergic reactions to certain medicines, an insect sting or certain types of food can also cause the release of histamine, leading to urticaria.
• Chronic urticaria can sometimes be due to an autoimmune reaction - this is when antibodies from your immune system attack your own body, causing your skin cells to release histamine. If you have chronic urticaria, certain factors (such as some types of medicine, stress and alcohol) may make your urticaria worse.

However, the cause of urticaria often can't be found. Even when there are known trigger factors (such as with physical urticarias), it's not always clear why some people develop this type of reaction.

Complications of urticaria

Angioedema

If urticaria affects the deeper layers of your skin, it can cause even larger swellings, called angioedema.

Angioedema often affects your eyelids, lips and sometimes your mouth. These swellings may be painful, rather than itchy. You should visit your GP for advice if you get these symptoms.

If angioedema affects your airway, it may be hard for you to breathe, swallow or talk. Seek urgent medical attention if you have any of these symptoms.

Anaphylaxis

Very rarely, urticaria can develop into a more serious type of reaction called anaphylaxis. This is most common when urticaria is caused by an allergic reaction. Anaphylaxis is a severe allergic reaction affecting your whole body rather than just your skin. It can be life-threatening if you don't get medical help straight away.

If you develop anaphylaxis, you may have the following symptoms:

• feel faint or even collapse
• have trouble breathing
• feel sick or be sick
• have palpitations (when you can feel your heart beating faster)
• a feeling of anxiety or 'impending doom'

If you think you or any one else has symptoms of anaphylaxis, seek urgent medical attention.

Diagnosis of urticaria

Your GP will usually be able to diagnose urticaria just by examining your skin, or from what you tell him or her if your swellings have already gone down. He or she will try to find out what caused the reaction by asking you questions about when and where your urticaria came on. However, it's not always possible to identify a cause.

If your urticaria seems to have been a one-off episode, you probably won't need any treatment or further tests.

If your GP thinks your urticaria may have been caused by an allergy, he or she may refer you to a specialist for further tests. This may involve a skin-prick test to test for the suspected allergen (substance that causes an allergic reaction) or a blood test. If your doctor thinks you have a physical urticaria, he or she may carry out various tests to check whether the suspected cause (for example, cold or pressure to your skin) sets off a reaction.

Your GP may also check your blood pressure and pulse, listen to your chest and examine your ears, nose and throat. This is to check for signs of angioedema affecting your airway, or anaphylaxis. You will usually need to be admitted to hospital if you're found to have symptoms of these complications.

Your GP may refer you to a dermatologist (a doctor who specialises in skin conditions) or an immunologist (a doctor who specialises in conditions affecting your immune system) for further tests if your urticaria isn't responding to the usual treatments or if it keeps coming back.

Treatment of urticaria

Treatment of urticaria is aimed at relieving your symptoms and keeping your condition under control. Although there is no cure, there is a good chance that you will eventually make a full recovery from your condition, whatever type of urticaria you have.

Medicines

Antihistamines
Your GP may advise you to take an antihistamine to control your symptoms. These medicines reduce the itching in most people. Your GP may prescribe antihistamines, and you can also buy them over-the-counter at your pharmacy. If your symptoms don't respond to the treatment, your GP may advise you to try a different type of antihistamine after a couple of weeks, or he or she may increase the dose of your medicine.

Some antihistamines are sedating (make you feel sleepy). Your GP may prescribe one of these for you to take at night if the itch is stopping you from sleeping.

Steroids
If you have a flare-up of severe symptoms, your GP may prescribe a short course of steroid tablets in addition to antihistamines. The steroids may help to make symptoms of severe urticaria go away quicker.

Immunosuppressants
Very occasionally, you may be given newer treatments (eg ciclosporin) that work by suppressing your immune system. These are only given to the most severely affected people, and usually by doctors in specialist skin and allergy centres.

Always ask your doctor or pharmacist for advice and read the patient information leaflet that comes with your medicine.

For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.