Urticaria (also known as nettle rash) is an itchy rash caused by tiny amounts of fluid that leak from blood vessels just under the skin surface. In chronic urticaria, it persists for more than six weeks, although often on and off.
If you have hives (urticaria), you have an itchy rash with raised areas called weals (or wheals), which are white or red. There may be blotchy areas. The rash tends to come and go and it may move around.
In some people with hives, more serious swelling can develop - for example, in the mouth, or tongue or face. This related condition is called angio-oedema, and is discussed in a separate leaflet. It can get in the way of breathing and can be a medical emergency.
Possible causes include:
- Something touching the skin.
- Heat or cold.
- An autoimmune reaction - the body over-reacting and causing damage to itself.
See separate leaflet called Hives (Inducible Urticaria). This gives you further information about the type of hives which is caused by a physical stimulus (such as touch, heat, cold, vibration, etc).
What are hives?
When you have hives (urticaria), you have an itchy rash caused by tiny amounts of fluid that leak from blood vessels just under the skin surface.
Hives can be acute (meaning the rash comes on suddenly and lasts less than six weeks) or chronic (meaning the rash hangs about, on and off, for longer.) This leaflet deals only with hives when they are chronic.
What are the symptoms of hives?
An itchy rash is the main symptom of hives (urticaria). The rash can affect any area of skin. Small raised areas called weals develop on the skin. The weals look like mild blisters and are itchy. Each weal is white or red and is usually surrounded by a small red area of skin which is called a flare. The weals are commonly 1-2 cm across but can vary in size. There may be just a few but sometimes many develop over various parts of the body. Sometimes weals that are next to each other join together to form larger ones. The weals can be any shape but are often round.
As a weal fades, the surrounding flare remains for a while. This makes the affected area of skin look blotchy and red. The blotches then fade gradually and the skin returns to normal. Each weal usually lasts less than 24 hours. However, as some fade away, others may appear. It can then seem as if the rash is moving around the body. The rash may clear completely only to return a few hours or days later.
Are there any other symptoms?
- The appearance of the rash and the itch can cause distress.
- A related condition called angio-oedema occurs from time to time in some people with persistent hives (chronic urticaria). In this condition some fluid also leaks into deeper tissues under the skin, which causes the tissues to swell:
- The swelling of angio-oedema can occur anywhere in the body but most commonly affects the eyelids, lips and genitals.
- Sometimes the tongue and throat are affected and become swollen. The swelling sometimes becomes bad enough to cause difficulty breathing.
- Symptoms of angio-oedema tend to last longer than urticarial weals. It may take up to three days for the swollen areas to subside and go.
- A variation called vasculitic hives occurs in a small number of cases. In this condition the weals last for more than 24 hours, they are often painful, may become dark red and may leave a red mark on the skin when the weal goes. Technically, this type of rash is not urticaria.
Are hives serious?
The rash is usually itchy. Each weal usually lasts less than 24 hours. However, as the rash may constantly come and go, the ongoing itch may cause distress and difficulty sleeping. If there is angio-oedema as well, it can be more serious, as it can cause serious breathing difficulties.
What causes hives?
A trigger causes cells in the skin to release chemicals such as histamine. The chemicals cause fluid to leak from tiny blood vessels under the skin surface. The fluid pools to form weals. The chemicals also cause the blood vessels to open wide (dilate) which causes the flare around the weals. The trigger is not known or identified in many cases. Possible causes in some cases include the following:
- In many cases the cause may be an autoimmune problem. Autoimmune means that our own immune system causes damage to some of our body's own cells. Normally, our body makes proteins called antibodies to fight infections - for example, when we catch a cold or have a sore throat. These antibodies help to kill the germs causing the infection. In autoimmune diseases the body makes similar antibodies (autoantibodies) that attack its normal cells. In hives (urticaria), these antibodies attach to cells under the skin and cause them to release histamine and other chemicals. The reason why this happens is not clear.
- Stress, infections or medicines may be a trigger in some cases.
- An allergy to a food, medicine or parasite (such as worms in the gut) is an uncommon cause of hives. A skin specialist may advise tests if an allergy is suspected.
- Inducible urticaria - sometimes called physical urticaria. This is a type of hives in which a rash appears when the skin is physically stimulated. The most common example of this is called dermatographism (dermatographia) - a rash develops over areas of skin which are firmly stroked. In other cases an urticarial rash is caused by heat, cold, emotion, exercise, or strong sunlight. See separate leaflet called Hives (Inducible Urticaria) for more details. This kind of hives often causes bouts of sudden-onset (acute) symptoms, but sometimes causes chronic symptoms.
Types of hives
Hives (urticaria) can be classed as follows:
- Acute - if it develops suddenly and lasts less than six weeks. Most cases last 24-48 hours. About 1 in 6 people will have at least one bout of hives in their lives. It can affect anyone at any age. Some people have repeated bouts of hives. See separate leaflet called Hives (Acute Urticaria) for more details.
- Chronic - if it persists long-term. (Chronic means persistent or ongoing.) In the chronic condition, a rash develops on most days for at least six weeks. This is uncommon. About 1 in 1,000 people develop chronic urticaria at some stage in their lives. It is more common in women than it is in men. Some people have an urticarial rash on and off for months, or even years.
Are any tests needed?
Tests are often not needed or helpful. Which tests are needed depends on the pattern of when the rash comes.
A symptom diary
A symptom diary may be helpful in working out if there is a specific trigger or cause. If your diary shows you only develop the rash on days when you eat a certain food, for example, it may be obvious what the cause is. A diary might also show if the rash relates to stress, exercise or sunlight. It may help rule out certain causes.
Skin-prick allergy tests
In some cases if it appears to be related to an allergy, tests such as skin-prick allergy tests may be helpful. Tiny quantities of substances which might cause an allergy are placed on your skin in a special order. If the skin reacts, you may be allergic to that substance.
In other cases, blood tests for allergy may be useful. In some people, blood tests may help to point to a cause. These may be general blood tests, or blood tests to look for specific proteins produced by your immune system, called autoantibodies. Where these are found, it is likely that it is your own immune system over-reacting which is causing the rash.
In some people, 'exclusion' or 'challenge' tests may be needed. For example, testing to see if cold or pressure always causes the rash, or excluding certain foods from the diet to see if that stops the rash from coming back.
What are the treatments for persistent hives?
The release of a chemical called histamine under the skin is involved in causing hives (urticaria). Antihistamines block the action of the histamine. Most affected people have at least partial relief, and sometimes total relief, of their symptoms with antihistamines. The most commonly used antihistamines for hives are cetirizine, fexofenadine and loratadine. These do not usually cause drowsiness. Your doctor may advise doses which are higher than the usual recommended dose in order to control the rash. If the itch is making it difficult to sleep, sometimes an antihistamine which makes you sleepy can also be taken at night. Examples of antihistamines used in this way include chlorphenamine or hydroxyzine.
Antihistamines can be bought over the counter without a prescription. However, if you need to take them for more than a few days, it is best to see your doctor for further advice. Do not take more than the recommended dose without discussing it with your doctor. Antihistamines are not usually advised in pregnancy.
Soothing the rash
Creams such as menthol in aqueous cream are useful to cool the skin and help to relieve itch. Calamine lotion can also help. A tepid bath or shower may relieve the itch before bedtime and help you to sleep.
Avoiding triggers or aggravating factors
Occasionally a trigger such as a food is identified as causing the rash. You may then be able to avoid it. However, it is unusual to identify a trigger. For example, if a food trigger is suspected then you may be asked to keep a food diary to try to identify which food is responsible.
Various other factors may make symptoms worse (but are not the main trigger). The following are tips that some people have found helpful; however, there is little proof that they work in everybody:
- Try avoiding tight clothes if weals occur at sites of local pressure. For example, under belts, under tight-fitting shoes, etc.
- Try keeping cool, as hives may tend to flare up in warmer conditions. In particular, keep the bedroom cool at night.
- For some people alcohol, hot baths, strong sunlight, and undue emotion make symptoms worse. If you think any of these are making symptoms worse then it may be helpful to avoid them.
- See a doctor if you think a medicine is making symptoms worse, as a change in medication may be an option. Some medicines that may be triggers include aspirin, anti-inflammatory painkillers, and angiotensin-converting enzyme (ACE) inhibitors.
Steroids reduce inflammation and may ease hives. However, it is not a usual treatment, due to the serious side-effects which are likely to occur if you take steroids regularly. A short course of steroids may be advised occasionally for a bad flare-up of symptoms. The steroid usually used is prednisolone, taken daily for seven days.
If antihistamines are not working, you may be referred to a specialist. This might be a skin specialist (dermatologist) or a specialist in the immune system (immunologist). Other treatments for severe chronic urticaria which may be tried by a specialist include:
- Omalizumab. This is a newer medication which acts against autoantibodies produced by the body's own immune system. It has to be given by injection once a month. It is very effective for chronic urticaria but the rash may return when the injections are stopped.
- Ciclosporin. This medication suppresses the immune system. This isn't often used as there is a risk of serious side-effects.
- Tablets such as montelukast, usually used for asthma. This also acts on the immune system.
- Dietary advice from a nutritionist if there is any evidence that any kind of food is a trigger for your rash. For most people there is no evidence that diet changes are helpful.
Treatment of associated angio-oedema
Antihistamines usually help to reduce the swelling of angio-oedema. Occasionally, an adrenaline (epinephrine) injection and emergency hospital treatment are necessary if anaphylaxis occurred. See separate leaflet called Angio-oedema for more details.
What is the outlook for persistent hives?
Persistent hives (chronic urticaria) tend to come and go. You may have times when the rash appears on most days, and then times when the rash may go away for a while. The severity of the rash and itch varies from person to person. Some things such as heat, cold, menstrual periods, stress, or emotion may make the rash flare up worse than usual.
- Symptoms may go away completely after a few months; however, the condition lasts several years in some cases.
- In about half of cases, symptoms go within 3-5 years after the condition first starts.
- In about 1 in 5 cases the symptoms persist on and off for more than 10 years.
Further reading and references
BSACI guideline for the management of chronic urticaria and angioedema; British Society for Allergy and Clinical Immunology (Feb 2015)
Urticaria; NICE CKS, May 2016 (UK access only)
Zuberbier T, Aberer W, Asero R, et al; The EAACI/GA(2) LEN/EDF/WAO Guideline for the definition, classification, diagnosis, and management of urticaria: the 2013 revision and update. Allergy. 2014 Jul69(7):868-87. doi: 10.1111/all.12313. Epub 2014 Apr 30.
Urticaria; DermNet NZ
Urticaria and angio-oedema: an overview; Primary Care Dermatology Society
Omalizumab for previously treated chronic spontaneous urticaria; NICE Technology Appraisal Guidance, June 2015
Sharma M, Bennett C, Cohen SN, et al; H1-antihistamines for chronic spontaneous urticaria. Cochrane Database Syst Rev. 2014 Nov 14(11):CD006137. doi: 10.1002/14651858.CD006137.pub2.
Briefly I had just over 6 weeks of daily urticaria in 2015. I was prescribed prednisolone on a tapered dose which had to be repeated a couple of times. I've no idea what caused it. At the time I kept...beverley1956
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