Urticaria – also known as hives, welts or nettle rash – is a raised, itchy rash that appears on the skin.
The rash can be on just one part of the body or be spread across large areas.
The affected area may change in appearance within 24 hours, and the rash will usually settle within a few days. If it clears completely within six weeks, it's known as acute urticaria.
Sometimes the rash can persist or come and go for more than six weeks, often over many years, although this is less common. Doctors refer to this as chronic urticaria.
Who's affected by urticaria?
Urticaria is a common condition. It's estimated that around 1 in 6 people will have it at some point in their lives.
Children are often affected by the condition, as well as women between 30 and 60 years of age, and people with a history of allergies.
Long-term urticaria is much less common, affecting around 1 in 1,000 people in England. Women are twice as likely to develop chronic urticaria as men.
What causes urticaria?
Urticaria occurs when a trigger causes high levels of histamine and other chemical messengers to be released in the skin.
These substances cause the blood vessels in the affected area of skin to open up (often resulting in redness or pinkness) and become leaky. This extra fluid in the tissues causes swelling and itchiness.
Histamine is released for a wide range of reasons, including:
an allergic reaction to substances such as latex
cold or heat exposure
the effect of certain chemicals found in some types of food and medications, such as non-steroidal anti-inflammatory drugs (NSAIDs)
However, in over half of short-term urticaria cases, no obvious cause can be found.
There's also no obvious cause in many cases of long-term urticaria. However, most experts think that it's often caused by the immune system mistakenly attacking healthy tissue.
Certain triggers may also make the symptoms worse. These include:
drinking alcohol or caffeine
Your GP will usually be able to diagnose urticaria by examining the rash on your skin.
They will want to find out what triggered your symptoms so you can avoid it in future. They may ask you a number of questions including:
when and where it began
what you had to eat just before it began and details of your usual diet
whether you started taking any new medication just before symptoms began
whether you live or work in an environment where you come into contact with possible triggers, such as pets, chemicals or latex gloves
If your GP suspects that it's caused by an allergic reaction, you may be referred to an allergy clinic for an allergy test.
If you've had urticaria most days for more than six weeks, it's unlikely to be the result of an allergy, so allergy tests aren't usually recommended.
However, your GP should ask about anything that makes your symptoms worse, such as medicines, as well as your alcohol and caffeine consumption and your stress levels.
You may also be referred for a number of tests, including a full blood count (FBC) and other tests, to find out whether there's an underlying cause of your symptoms.
In many cases, treatment isn't needed for urticaria because the rash often gets better within a few days.
If the itchiness is causing you discomfort, a medication calledantihistamine can help. Antihistamines are available over the counter at pharmacies. Speak to your pharmacist for advice.
A short course of steroid tablets (oral corticosteroids) may occasionally be needed for more severe cases of urticaria.
If you have persistent urticaria, you may be referred to a skin specialist (dermatologist). Treatment usually involves medication to relieve the symptoms, while identifying and avoiding potential triggers.
Complications of urticaria
Around a quarter of people with acute urticaria and half of people with chronic urticaria will also develop swelling in a deeper layer of skin.
This is known as angioedema and it can cause severe swelling in different parts of the body, such as the eyes, lips and genitals.
Medication such as antihistamines and short courses of oral corticosteroids (tablets) can be used to relieve the swelling.
Steroid injections may be needed for more severe cases of angioedema. They're usually given in hospitals or specialist clinics by an allergy or immune system specialist.
Urticaria, also known as hives, welts or nettle rash, is a raised, itchy rash
Urticaria can be one of the first symptoms of a severe allergic reaction known as anaphylaxis.
Other symptoms of anaphylaxis include:
swollen eyes, lips, hands and feet
feeling lightheaded or faint
narrowing of the airways, which can cause wheezing and breathing difficulties
abdominal pain, nausea and vomiting
collapse and unconsciousness
Anaphylaxis should always be treated as a medical emergency.
Dial 999 immediately and ask for an ambulance if you or someone else is experiencing anaphylaxis. Tell the operator about your (or their) symptoms.
Symptoms of urticaria
The main symptom of urticaria is a red, raised, itchy rash.
The rash is made up of raised marks in the skin, known as weals or hives. They're usually very itchy and range in size from a few millimetres to the size of a hand.
Individual weals usually fade after a few hours, but can be replaced by new ones elsewhere on the body. They may appear on just one part of the body or across a large part of it. The skin returns to normal as soon as the weal fades.
Pattern of symptoms
Most cases of urticaria are temporary (known as acute urticaria). The rash appears suddenly and is most severe after 8-12 hours, but usually goes away within 24 hours (although it can occasionally last for 48 hours).
The pattern of symptoms in long-term (chronic) urticaria can be unpredictable.
One small survey found that around half of people with chronic urticaria have outbreaks of symptoms that last for 6-12 weeks, followed by periods when their symptoms improve or disappear completely (remission).
Certain triggers such as stress or alcohol can make symptoms worse.
The same survey also found that 1 in 10 people had persistent symptoms of urticaria that lasted all year round.
Symptoms of chronic urticaria are often most troublesome in the evening, which can make falling asleep difficult.
When to seek medical advice
Visit your GP if your symptoms don't go away within 48 hours.
You should also contact your GP if your symptoms are severe, causing distress and disrupting daily activities.
You may need a short course of steroid tablets (oral corticosteroids) if other measures aren't able to control the symptoms.
Urticaria vasculitis is a rare type of urticaria that causes the blood vessels inside the skin to become inflamed.
In urticaria vasculitis, the weals last longer than 24 hours, they're more painful and can leave a bruise. If you have urticaria vasculitis, you may be referred to a skin specialist (dermatologist).
Media last reviewed: 24/01/2014
Next review due: 24/01/2016
Causes of urticaria
Urticaria occurs when histamine and other chemicals are released from under the skin's surface, causing the tissues to swell.
The triggers of short-term (acute) urticaria are unknown in around half of all cases.
Recognised triggers include:
a food allergy to foods such as peanuts, shellfish, eggs and cheese
an allergic reaction to environmental factors such as pollen, dust mites or chemicals
an allergic reaction to latex, which can be a common problem in healthcare workers
infections, which can range from relatively trivial, such as a cold, to very serious, such as HIV
insect bites and stings
certain medications that can cause urticaria as a side effect, including antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs) and aspirin
physical triggers, such as pressure to the skin, changes in temperature, sunlight, exercise or water
Long-term (chronic) urticaria may occur when the body's immune system attacks its own tissues. This is known as an autoimmune reaction.
Antibodies (proteins that usually fight bacteria and viruses) then trigger the release of histamine, resulting in urticaria.
About a third to half of all chronic cases of urticaria are thought to be autoimmune related.
It's not known why autoimmune urticaria develops, although it can sometimes occur in combination with other autoimmune conditions, such as:
rheumatoid arthritis – when the immune system attacks the joints
lupus – when the immune system attacks the joints and skin, and people usually feel tired all the time
Chronic urticaria can also be linked to other chronic illnesses and infections, such as viral hepatitis (liver infection), intestinal parasites, an underactive thyroid gland (hypothyroidism) or an overactive thyroid gland (hyperthyroidism).
Chronic urticaria tends to come and go. Many people find that certain things make it reappear or make existing symptoms worse. Triggers include:
prolonged pressure on the skin – this can happen by wearing tight clothing
medications – such as NSAIDs, and the painkiller codeine
certain food additives – such as salicylates, which are found in tomatoes, orange juice and tea
insect bites and stings
exposure to heat, cold, pressure or water
ACE inhibitors that are often used to treat high blood pressure(hypertension) can be associated with deeper swellings ofangioedema.
Short-term urticaria can be diagnosed by examining the distinctive red rash.
If you have severe or persistent urticaria, you may need to have a number of tests to try and identify the underlying cause (see below).
Your GP will usually be able to diagnose short-term (acute) urticaria by examining the rash on your skin.
They will want to find out what triggered your symptoms so you can avoid it in the future. The type of things they may ask you include:
when and where the rash began
what you had to eat just before it began and details of your usual diet
if you started taking any new medication just before your symptoms began
if you live or work in an environment where you come into contact with possible triggers, such as pets, chemicals or latex gloves
if you were stung or bitten by an insect just before your symptoms started
the current state of your health and if you've had any recent infections
if you've recently travelled to a foreign country and if so, where
if there's a history of urticaria in your family
In around half of all cases of acute urticaria, a cause can't be identified.
If your GP thinks that your symptoms are caused by an allergic reaction, you may have to go to an allergy clinic.
Tests may be carried out on either your skin or your blood to find out if you're allergic to suspected triggers for urticaria, such as foods and latex.
If you have urticaria that lasts for more than six weeks, it's very unlikely that it's causd by an allergy, so allergy tests aren't usually recommended.
However, your GP should ask about anything that makes your urticaria worse, such as medicines, your alcohol and caffeine consumption, and stress levels.
You may also be referred for a number of tests to find out if there's an underlying cause of your chronic urticaria. These tests may include:
a full blood count test, which can identify anaemia
tests to determine the levels of antibodies in your blood
a stool sample, which can identify intestinal parasites
an erythrocyte sedimentation rate (ESR) test, which can help identify problems with your immune system
thyroid function tests, which can be used to check for an underactive thyroid gland (hypothyroidism) or an overactive thyroid gland (hyperthyroidism)
liver function tests, which can be used to check if you have any problems with your liver
Most cases of urticaria don't need treatment because the symptoms are usually mild and often get better within a few days.
If your symptoms are troublesome or persistent, antihistamine medication is available over the counter from pharmacies.
See your GP or speak to your pharmacist if your symptoms get worse. If your symptoms are very severe, your GP may prescribe other medications, such as corticosteroid tablets. Go back to your GP if your symptoms get worse or if the treatment hasn't worked after two weeks.
Antihistamines block the effects of histamine, so help stop the itchiness and reduce the rash. Examples of antihistamines include:
In most people, modern antihistamines don't cause drowsiness, although there are some exceptions. See how you react to the antihistamine before driving or operating heavy machinery. Antihistamines may also cause drowsiness if taken with alcohol. Always read the information leaflet that comes with the medication.
Antihistamines aren't usually prescribed to pregnant women, as it's unknown whether they're entirely safe. However, chlorphenamine may be recommended if it's believed that the benefits outweigh the risks. There is no evidence that chlorphenamine harms unborn babies.
You may be prescribed a short course of high-dose corticosteroid tablets, such as prednisolone, if your symptoms are severe.
Corticosteroids suppress your immune system, which reduces the symptoms of urticaria. A course of prednisolone lasting between three and five days is usually recommended.
Taking steroid tablets on a long-term basis isn't usually recommended because it can lead to a wide range of side effects and complications, such as high blood pressure (hypertension), glaucoma, cataractsand diabetes (or it can make existing diabetes worse).
Treatment for persistent urticaria involves trying to control your symptoms and avoiding any triggers that make them worse.
If you have chronic urticaria and angioedema (swelling of a deeper layer of skin), you may be referred to a dermatologist (skin specialist). This is because angioedema is potentially more serious and can cause breathing difficulties.
You should also be referred to a dermatologist if you just have chronic urticaria and the symptoms continue, despite treatment.
Chronic urticaria is treated with antihistamines. You may have to take them regularly for as long as your symptoms last. As with short-term urticaria, you may be given a combination of non-drowsy and drowsy antihistamines to help you sleep.
An increased dose may be recommended if your symptoms don't respond to treatment. Increasing the dose can often help control symptoms that previously didn't respond to treatment. However, this should only be carried out under the instruction of the doctor in charge of your care.
A newer type of antihistamine called rupatadine has proved effective in treating more severe cases of chronic urticaria that don't respond to other antihistamines. The doctor in charge of your care can tell you if you could benefit from taking rupatadine.
Menthol cream can be used as an alternative or in addition to antihistamines because it helps relieve itchiness. Your GP can prescribe this.
Occasionally, more serious episodes of urticaria can be treated with short doses of corticosteroid tablets, such as prednisolone. Possible side effects of corticosteroid tablets include increased appetite and weight gain, mood change and difficulty sleeping (insomnia).
Long-term use of corticosteroids in chronic urticaria isn't recommended for the reasons mentioned above.
The type of antihistamines you can get from the pharmacist are known as H1 antihistamines. However, there are several other types of antihistamines, including H2 antihistamines.
H2 antihistamines can sometimes be useful in treating chronic urticaria because they narrow blood vessels. This can often help reduce the redness of the skin.
H2 antihistamines can be used as an alternative to H1 antihistamines or in combination with them. Side effects of H2 antihistamines are uncommon, but include:
Don't drive or use tools or machinery if you feel dizzy after taking a H2 antihistamine.
Narrowband ultraviolet B phototherapy
Narrowband ultraviolet B phototherapy (NUVB) is a treatment that involves exposing areas of your skin to high-energy ultraviolet light. The light can help clear an otherwise persistent rash.
NUVB involves standing in a chamber that's similar in appearance to a shower. The chamber contains a number of fluorescent light bulbs which your skin is exposed to for a short period of time, usually just a few minutes.
You'll usually have between two and five sessions of NUVB a week. Most people need around 20 sessions before their symptoms improve significantly.
The light can cause your skin to burn, similar to a mild sunburn. You'll be given a cream to help soothe any burning.
Exposure to ultraviolet light carries a theoretical risk of causing skin cancer in later life. It's not clear exactly how high this risk is because NUVB is a relatively new treatment. However, most experts think the risk is small.
Leukotriene receptor antagonists
Leukotriene receptor antagonists are a type of medication that can help reduce redness and swelling of the skin.
They can be a useful long-term alternative to using corticosteroid tablets because they don't carry the same risk of causing wide-ranging side effects.
The side effects of leukotriene receptor antagonists are rare and relatively minor. They include headaches and nausea (feeling sick).
In around two-thirds of cases, a powerful medication called ciclosporin has proved effective in treating urticaria.
Ciclosporin works in a similar way to corticosteroids. It suppresses the harmful effects of the immune system and is available in capsule form or as a liquid.
Side effects of ciclosporin include:
high blood pressure (hypertension)
increased levels of blood cholesterol
involuntary shaking (tremors)
increased vulnerability to infection, particularly chest infections, urinary tract infections (UTIs) and a type of viral infection known as cytomegalovirus
There are also a number of other side effects that can occur when taking ciclosporin and you should discuss these thoroughly with your doctor before starting.
Side effects, such as high blood pressure and high cholesterol, are a particular cause for concern because they can increase your risk of heart disease and stroke.
Even if you still respond to treatment, it may be recommended that the medication is withdrawn after a few months.
For urticaria that hasn't responded to antihistamines, there are newer medications becoming available, such as omalizumab. Omalizumab is given by injection and is thought to reduce a type of antibody that can play a part in urticaria.
There's some uncertainty over the role of diet in people with long-term urticaria. There are two groups of chemicals in foods that may trigger urticaria in some people – vasoactive amines and salicylates (see below).
Avoiding or reducing foods that contain these chemicals may help improve your symptoms.
You could also keep a food diary to see whether avoiding certain foods helps your symptoms. If you restrict your diet, consult a dietitian, who can make sure that you're not avoiding foods unnecessarily and that your diet is healthy.
Foods that contain vasoactive amines or cause histamine release include:
Salicylates are naturally occurring aspirin-like compounds that are found in a wide variety of foods of plant origin. You can try cutting down on these, but don't completely avoid them. Foods that contain salicylates include:
If you know what triggers your urticaria or makes it worse, avoiding the trigger may help keep your symptoms under control.
Triggers such as alcohol and caffeine can be easily avoided. If you think a certain medication may be triggering your symptoms, contact the doctor who prescribed it, because alternatives may be available.
Avoiding stress can be more difficult, particularly if your symptoms negatively affect your quality of life.
If you have severe or persistent urticaria, you may find that relaxation techniques, such as meditation or hypnosis, help reduce your stress levels and the severity of your symptoms.
Complications of urticaria
Around half of people with persistent (chronic) urticaria and a quarter of people with short-term (acute) urticaria also develop a related condition called angioedema.
Chronic urticaria can be upsetting and negatively impact a person's mood and quality of life.
Angioedema is swelling in the deeper layers of a person's skin. It's often severe and is caused by a build-up of fluid.
The symptoms of angioedema can affect any part of the body, but usually affect the:
The swelling often appears suddenly and is much more severe than normal hives. It usually lasts between one and three days. Occasionally, it can be caused by medications such as ACE inhibitors, which are used to treat high blood pressure (hypertension).
As well as visible swellings, angioedema can also cause some or all of the following symptoms:
a burning hot or painful sensation in the swollen areas
swelling of the inside of the throat, the air tubes in the lungs and the tongue, making breathing difficult.
swelling of the transparent layer of cells that cover the white part of the eye (conjunctiva), which affects vision
Medication, such as antihistamines and steroid tablets (oral corticosteroids), can be used to stop the swelling. Steroids are usually only given for short periods because they can have significant side effects when used over the long term.
Steroid injections may be needed in more severe cases of angioedema, when a person has breathing difficulties. These are usually given in hospitals or specialist clinics by an allergy or immune system specialist.
Living with any long-term condition can be difficult. For people with chronic urticaria, it can have a considerable negative impact on their mood and quality of life. Living with itchy skin can be particularly upsetting.
One study found that chronic urticaria can have the same negative impact as heart disease. It also found that one in seven people with chronic urticaria had some sort of psychological or emotional problem, such as stress, anxiety and depression.
See your GP if your urticaria is getting you down. Effective treatments are available to help improve symptoms of stress, anxiety and depression.