Urticaria (hives): symptoms, causes, treatment and how long it lasts

NHS inform says the rash may be raised, very itchy, limited to one part of the body or spread over large areas, and anywhere from a few millimetres to the size of a hand. The NHS adds that it can sting or burn.

On white skin the rash usually looks pink or red. The NHS notes that colour can be harder to see on brown and black skin, where the wheals may look skin-coloured or slightly lighter or darker and puffy. Feeling the raised surface helps.

Some people also develop angioedema, a deeper swelling. CKS describes it as a deeper form of urticaria affecting tissues under the skin and the lining of the mouth and throat.

Urticaria is a swelling in the top layers of the skin that produces a red, raised, itchy rash. Each patch is called a wheal. The cause is the release of histamine and other chemicals from cells in the skin, which makes tiny blood vessels leak and the tissue swell.

Individual wheals tend to come and go. A patch may fade within hours while new ones appear elsewhere. This shifting pattern separates hives from many other rashes, where the same area stays affected for days.

For mild hives a pharmacist can advise on antihistamines. NHS inform notes these may not suit young children or people with some long-term conditions, so tell the pharmacist about your health.

CKS says people whose symptoms need treatment should be offered a non-sedating antihistamine taken daily for up to 6 weeks, with a short course of an oral corticosteroid of up to 7 days for severe symptoms. If this works and symptoms are likely to persist, daily antihistamine for 3 to 6 months may be considered. If it does not work, doctors can consider a higher dose of the first antihistamine, an alternative one, calamine lotion for itch, or a sedating antihistamine at night when itch disturbs sleep.

Referral to a dermatologist or immunologist is advised in certain situations, such as suspected vasculitic urticaria or a food or latex allergy. CKS also advises psychological support when the condition harms quality of life.

A GP might prescribe menthol cream, antihistamines or steroid tablets, according to the NHS, and may refer you to a skin specialist (dermatologist) if hives do not go away with treatment.

The NHS says hives rashes usually get better within a few days. NHS inform says most hives rashes do not need treatment and the symptoms are usually mild.

NICE CKS classifies urticaria by duration. Acute urticaria lasts under 6 weeks and is likely to be self-limiting without treatment. Chronic urticaria persists for 6 weeks or longer on a nearly daily basis. In CKS terms, antihistamine treatment can be considered daily for 3 to 6 months if symptoms are likely to be persistent or recurrent.

NHS inform says individual patches can change in appearance within 24 hours. Ask for an urgent GP appointment or call NHS 111 if the rash has not improved after 2 days or keeps coming back.

NHS inform lists many possible triggers: certain foods, insect bites or stings, cold, heat from exercise or spicy food, emotional stress, infections such as a cold, alcohol or caffeine, medicines including anti-inflammatory painkillers and antibiotics, pollen, dust mites, chemicals, latex, tight clothing and a problem with the immune system. Water or sunlight is a rare trigger.

The NHS suggests trying to find out what sets off your hives so you can avoid it when possible. In chronic urticaria a clear trigger is often not found, which can be frustrating but is a recognised pattern rather than a sign that something has been missed.

NICE CKS classifies urticaria by duration. Acute urticaria lasts under 6 weeks. Chronic urticaria goes on for 6 weeks or longer, on nearly every day. Acute episodes are likely to settle by themselves.

Chronic urticaria has several forms. CKS lists chronic spontaneous urticaria, which has no identifiable outside cause but may be aggravated by heat, stress, certain drugs and infections. It also lists an autoimmune form and chronic inducible urticaria, formerly called physical urticaria, where a physical stimulus sets it off.

• Cold, heat, sunlight and water can each trigger an inducible form (aquagenic, solar, cold and heat urticaria).

• Dermatographism is a wheal pattern that appears where the skin is scratched or stroked.

• Delayed pressure and vibratory urticaria follow pressure on the skin or vibration.

• Contact urticaria follows touching a substance.

NHS inform says hives can usually be diagnosed by examining the distinctive rash. A pharmacist or GP may ask what could have triggered it. If symptoms last, a doctor may arrange tests to look for a cause and will ask what makes the rash worse.

CKS adds that tests are not usually required, but may be used after a thorough history and examination to find associated conditions or triggers, or to rule out other diagnoses.

Call 999 if the lips, mouth, throat or tongue suddenly swell, if breathing is very fast or hard, the throat feels tight or swallowing is difficult, the skin or lips turn blue, grey or pale, or someone becomes very confused, drowsy or faints. NHS inform lists these as signs of a serious allergic reaction.

Ask for an urgent GP appointment or call NHS 111 if hives have not improved after 2 days, the rash is spreading or keeps coming back, there is a high temperature and you feel unwell, you are worried about a child, or you have swelling under the skin.

Most people are looked after by a pharmacist or GP. The NHS says a GP can prescribe menthol cream, antihistamines or steroid tablets, and may refer you to a dermatologist if hives do not go away. NICE CKS lists referral to a dermatologist or immunologist if vasculitic urticaria is suspected, if there is a food or latex allergy, or for a form of inducible urticaria that may be difficult to manage in primary care.

People with persistent chronic urticaria sometimes choose a private dermatology or allergy appointment for specialist review. Whichever route you take, it helps to bring a diary of when the rash appears, what you ate, what you took and what you were doing.