Urticaria (also known as hives, welts or nettle rash) is a raised, itchy rash that appears on the skin. The rash can be limited to one part of the body or spread across large areas of the body.
The affected area of skin will typically change within 24 hours, and usually the rash will settle within a few days. If it clears completely within six weeks, it is known as acute urticaria.
Less commonly, the rash can persist or come and go for longer than six weeks, often over the space of many years. Doctors refer to this as chronic urticaria.
Read more about the symptoms of urticaria.
Many cases of hives don’t need treatment as the rash often gets better within a few days. If you’re struggling with it, a medication called antihistamine usually helps. Antihistamines are available over-the-counter at pharmacies. Speak to your pharmacist for advice.
More severe cases may require a short course of steroid tablets (oral corticosteroids).
Long-term urticaria may need to be referred to a skin specialist (dermatologist) and treatment usually involves medication to relieve symptoms, while identifying and avoiding potential triggers (see below).
Read about the treatment of urticaria.
What causes urticaria?
Urticaria happens 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 causing redness or pinkness) and become leaky. This extra fluid in the tissues causes swelling and sometimes itchiness.
Histamine is released for a wide range of reasons, including:
- an allergic reaction to substances such as latex
- exposure to cold or heat
- the direct effect of certain chemicals which can be found in some types of food and medications, such as non-steroidal anti-inflammatory drugs (NSAIDs)
However, in over half of acute urticaria cases, no obvious cause can be found.
In most cases of long-term urticaria, there is no obvious cause. However, most experts think it's often caused by the immune system mistakenly attacking healthy tissue. Certain triggers make the symptoms worse, such as:
- drinking alcohol or caffeine
- emotional stress
- warm temperature
Read about the causes of urticaria.
Who is affected?
Urticaria is a common condition. It is estimated that around one person in six will have hives at some point.
The condition is most common in children, women aged 30–60 years old and people with a history of allergies.
Around a quarter of people with acute urticaria and half of people with chronic urticaria will also develop swelling of a deeper layer of skin.
This is known as angioedema. It can cause severe swelling in different parts of the body, such as the eyes, lips and genitals.
Read about the complications of urticaria.
The main symptom of urticaria is a red, raised, itchy rash.
The rash is made up of raised marks in the skin that are known as weals or hives. They are usually very itchy and range in size from a few millimetres to the size of a hand.
Individual weals normally 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 (acute urticaria). The rash appears quickly, becomes most severe after 8–12 hours and then normally resolves within 24 hours (although it can occasionally persist for 48 hours).
The pattern of symptoms in chronic hives 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 times where their symptoms improve or go away all together (remission).
Certain triggers such as stress or alcohol can make symptoms worse. Read about the triggers of urticaria.
The same survey 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
You should visit your doctor if your symptoms do not resolve within 48 hours.
Also contact your doctor if you have severe symptoms that are causing distress and disrupting your daily activities. You may need a short course of steroid tablets (oral corticosteroids.
Read about treating hives.
Urticaria is caused by the release of histamine and other chemicals from under the skin's surface, causing the tissues to swell.
What triggers acute urticaria is unknown in around half of cases. Recognised triggers include:
- an allergic reaction to food, 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
- emotional stress
- some medications, which can cause urticaria as a side effect, including antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, and antihistamines
- physical triggers, such as pressure to the skin, change in temperature, sunlight, exercise or water
Chronic urticaria may start when your 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.
This produces urticaria. It is thought that about a third to half of chronic urticaria cases are autoimmune.
It is not known why autoimmune urticaria develops, although it can often develop in combination with other autoimmune conditions such as:
- rheumatoid arthritis – the immune system attacks the joints
- lupus – the immune system attacks the joints and skin, and people usually feel very tired all the time
In rarer cases, chronic urticaria can also be caused by other chronic illnesses and infections, such as an underactive thyroid gland or overactive thyroid gland, viral hepatitis (liver infection) or intestinal parasites.
Chronic urticaria often comes and goes. Many people find that certain things make it reappear or make existing symptoms worse. These triggers include:
- warm temperatures
- prolonged pressure on the skin (for example, from tight clothing)
- medications such as NSAIDs, the painkiller codeine and ACE inhibitors (used to treat high blood pressure)
- 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
Acute urticaria is usually diagnosed by examining the rash on your skin. Your doctor will also want to find out what triggered your symptoms, so you can avoid it in future.
They will ask you:
- when and where it began
- what you had eaten just before the urticaria started and what you normally eat
- whether you had started any new medication just before the symptoms began
- whether you live or work in an environment where you come into contact with any possible triggers, such as pets, chemicals or latex gloves
- if you had any insect stings or bites just before symptoms started
- about your current state of health, particularly if you have had any recent infections
- if you have recently travelled to a foreign country and, if so, where
- if there is a history of this condition in your family
A cause is never identified in half of cases.
If your doctor suspects that it is an allergic reaction, you may be referred to an allergy clinic.
Tests may be performed on either your skin or your blood to see if you are allergic to suspected triggers for urticaria, particularly foods and latex.
Read about testing for allergies.
If your urticaria lasts for more than six weeks, it is extremely unlikely that it is due to an allergy, so allergy tests are normally not recommended.
However, your doctor 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 the following tests to see if there is an underlying cause of your chronic urticaria:
- a full blood count test, which can identify anaemia
- 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 check whether you have an overactive or underactive thyroid gland
- liver function tests, which can check whether you have any problems with your liver
Most cases of urticaria will not need to be treated as the symptoms are mild and the condition often gets better on its own within a few days.
If the symptoms of acute urticaria are more serious or the condition persists, you can buy antihistamine medication over-the-counter at pharmacies. Speak to your pharmacist, or see your doctor if your symptoms get worse.
Your doctor may prescribe corticosteroid tablets, although you should return to your doctor if the symptoms get worse or treatment hasn't worked after two weeks.
Antihistamines block the effects of histamine, so they should stop the symptoms of itchiness and reduce the rash. Examples of antihistamines include:
Modern antihistamines do not cause drowsiness in most people, but there are some exceptions. See how you react to the antihistamine before driving or operating heavy machinery. Modern antihistamines may cause drowsiness if taken with alcohol. Always read the information leaflet for your medication.
If you are having problems sleeping at night because of particularly itchy urticaria, your doctor may give you additional antihistamines that are known to cause drowsiness, such as chlorphenamine or hydroxyzine.
Antihistamines are normally not prescribed during pregnancy. This is because they have not been established as being entirely safe. However, your doctor may recommend chlorphenamine if they feel the benefits outweigh the risk.
There are several thousand known cases of pregnant women taking chlorphenamine, and there is no evidence that it 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 and, therefore, can suppress the symptoms of urticaria.
Usually, a three- to five-day course of prednisolone is recommended.
Taking steroid tablets on a long-term basis is not usually recommended as this can lead to a wide range of side effects and complications, such as high blood pressure, glaucoma, cataracts and diabetes (or it can make existing diabetes worse).
Treatment for chronic urticaria involves helping you control your symptoms and avoiding any triggers that make the symptoms worse.
If you have chronic urticaria and angioedema (swelling of a deeper layer of skin), you may also be referred to a dermatologist (specialist in skin conditions). This is because angioedema is potentially more serious as it can cause breathing difficulties.
If you only have chronic urticaria but the symptoms persist despite treatment, you should also be referred.
The symptoms of chronic urticaria are treated with antihistamines. You may have to take them regularly for as long as the symptoms last. As with acute urticaria, you may be given a combination of non-drowsy and drowsy antihistamines to help you sleep.
If your symptoms do not respond to treatment, it may be recommended that you increase your dosage.
Increasing the dose can often help control symptoms that previously didn't respond to treatment. However, you should only do this if instructed to by 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 do not respond to other antihistamines.
The doctor in charge of your care should be able to tell you if you could benefit from taking rupatadine.
Menthol cream can be used as an alternative or in addition to antihistamines as it has been shown to relieve itchiness. Your doctor can prescribe this.
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 difficulties sleeping (insomnia).
Long-term use of corticosteroids in chronic urticaria is not recommended for the reasons mentioned above.
The type of antihistamines you can get from the pharmacist are known as H1 antihistamines.
But there are several other types of antihistamines, including H2 antihistamines.
These can be sometimes useful in treating chronic urticaria as they can narrow blood vessels. This in turn can often help reduce redness of the skin.
H2 antihistamines can be used in combination with H1 antihistamines or as an alternative to them.
Side effects of H2 antihistamines are uncommon but include:
If you feel dizzy after taking an H2 antihistamine, do not drive or use tools or machinery.
Narrowband ultraviolet B phototherapy
Narrowband ultraviolet B phototherapy (NUVB) is a type of treatment that involves exposing areas of your skin to high-energy ultraviolet light. The light can help clear an otherwise persistent area of rash.
NUVB involves standing in a chamber, much like a shower, that contains a number of fluorescent bulbs. Your skin is then exposed to the light for a short time, usually not more than a few minutes.
You would usually attend two to five sessions a week. Most people require 20 sessions before their symptoms significantly improve.
The light can cause some burning of the skin, similar to a mild sunburn. You can 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 is unclear exactly how high that risk is as this is a relatively new treatment, but most experts think the risk should be small.
Leukotriene receptor antagonists
Leukotriene receptor antagonists are a type of medication that can often reduce redness and swelling of the skin.
They can be a useful long-term alternative to using corticosteroid tablets as they do not carry the same high risk of causing wide-ranging side effects.
Side effects are uncommon and relatively minor, such as headaches and feeling sick.
A powerful medication called cyclosporin has proved effective in treating urticaria in around two-thirds of cases.
Cyclosporin works in the same way as corticosteroids do. It suppresses the harmful effects of the immune system and is available in capsule form or as a liquid that you drink.
Common side effects of cyclosporin include:
- high blood pressure
- increased levels of cholesterol in the blood
- involuntary shaking (tremors)
- increased vulnerability to infection, particularly chest infections, urinary tract infections (infection of any part of the body used to remove urine from the body) and a type of viral infection called cytomegalovirus
The longer a person takes cyclosporin, the less effective it tends to become. One study found that only one person in four was still free of symptoms after taking the medication for five months.
Side effects such as high blood pressure and high cholesterol are also a cause for concern as these 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.
There is controversy over the role of diet in people with long-term hives. There are two groups of chemicals in foods that may trigger urticaria in some people: vasoactive amines and salicylates.
Avoiding or reducing the intake of these chemicals may improve the symptoms.
You may wish to keep a food diary to see if avoiding a certain food helps your symptoms. If you restrict your diet, consult a dietitian, who can make sure that you are not avoiding foods unnecessarily and that your diet is adequate.
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 do not completely avoid them. Foods that contain salicylates include:
- orange juice
If you know what triggers your urticaria or makes it worse, avoiding the trigger may keep your condition under control.
Triggers such as alcohol and caffeine can be easily avoided. And if you think a particular medication may be triggering your symptoms, contact the doctor who prescribed it as alternatives may be available.
Avoiding stress can be harder, particularly if your symptoms negatively affect your quality of life.
If you have chronic urticaria, you may find that relaxation techniques, such as meditation or hypnosis, reduce your stress levels and the severity of your symptoms.
Around half of people with chronic (persistent) urticaria and a quarter of people with acute (short-term) urticaria also get a related condition called angioedema.
Angioedema is swelling in the deeper layers of the skin, usually in the eyelids, lips and sometimes the mouth, although it can occur anywhere.
The swelling is often severe and is caused by a build-up of fluid. The symptoms of angioedema can affect any part of the body, but they usually affect the:
The swelling often appears suddenly, and is much more severe than normal hives (nettle rash). It usually lasts for one to three days.
As well as visible swellings, angioedema can cause some or all of the following symptoms:
- a burning hot or painful feeling 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 (the conjunctiva), which affects vision
Steroid injections may be needed for more severe cases of angioedema, where a person has breathing difficulties. These are usually administered in hospitals or specialist clinics by an allergy or immune system specialist.
Read about the treatment of angioedema.
Emotional impact of chronic urticaria
Living with any long-term condition can sometimes be upsetting. For many people, chronic urticaria can have a considerable negative impact on their quality of life and mood.
Having to live with itchy skin can be particularly upsetting.
One study found that the condition can have the same negative impact as heart disease.
The same study found that one in seven people with chronic urticaria had some sort of psychological or emotional problem, such as stress, anxiety or depression.
Talking to friends and family can also help improve feelings of isolation and help you cope better with your condition.