Hives (Urticaria)

What are hives (urticaria)?

Hives, also called urticaria, are itchy, raised bumps or patches, known as wheals, that appear on the skin and often fade again within hours. It happens when your skin releases histamine and other chemicals, causing tiny blood vessels to leak fluid just beneath the surface.

What are the symptoms of hives?

The main symptom is an itchy rash. It can:

• appear as raised bumps or patches in many shapes and sizes
• show up anywhere on the body, in one area or spread more widely
• sting or burn as well as itch
• look pink or red on white skin, though this can be harder to see on brown or black skin
• change shape, move to different parts of the body, or fade in one spot and reappear in another.

Pressing the centre of a red hive often makes it turn white, which is a useful way to tell it apart from other rashes. Individual patches usually fade within 24 hours, though new ones can keep appearing, and hives themselves don't leave a lasting mark or bruise.

Hives can also occur alongside deeper swelling of the skin, called angioedema, which may affect the lips, tongue, mouth or throat. If this happens together with breathing difficulty, dizziness or swelling of the face, it can be a sign of a severe allergic reaction and needs urgent medical attention.

What are the causes of hives and who is at risk?

Hives happen when a trigger causes cells in your skin to release histamine and other chemicals. Often, no clear trigger can be found, especially if the hives keep coming back over a long period.

Common triggers include:

• certain foods, especially peanuts, eggs, nuts and shellfish
• medicines, such as some antibiotics, aspirin or ibuprofen
• insect stings or bites
• contact with plants, animals, chemicals or latex
• physical factors, such as pressure, cold, heat, exercise or sunlight
• infections, whether bacterial or viral
• emotional or physical stress.

You may be more likely to develop hives if you already have allergies, asthma or eczema. Episodes are most common in people in their 20s and 30s, though hives can affect anyone at any age.

Are there different types of hives?

The main distinction is between acute and chronic hives, based on how long they last:

• Acute spontaneous urticaria: The most common form, usually lasting from a few days up to six weeks, and generally easy to treat
• Chronic spontaneous urticaria: Symptoms persist for more than six weeks, sometimes for months or years, often without a clear trigger

There are also several types of hives with a specific physical trigger, sometimes called inducible or physical urticaria:

• Dermatographia: Urticaria caused by rubbing, scratching or scrubbing the skin
• Cold urticaria: This is triggered by contact with cold, which can be serious if it affects your whole body, for example after jumping into cold water
• Heat or cholinergic urticaria: Urticaria triggered by a rise in body temperature, such as from exercise, hot showers or anxiety
• Solar urticaria: This is triggered by sunlight
• Pressure urticaria: This caused swelling at points where pressure has been applied, such as under a tight belt
• Aquagenic urticaria: This type of urticaria is triggered by contact with water.

How are hives diagnosed?

For a single episode, hives can usually be diagnosed just by examining the rash. A pharmacist or GP may ask questions to help work out what triggered it, and whether you've been exposed to anything you've eaten, touched or taken as medicine.

If your hives last a long time or keep coming back, a doctor is more likely to ask about your medical history and any patterns you've noticed. They may suggest keeping a symptom diary noting when hives appear and how long each patch lasts.

Further tests aren't always needed, but may include:

• skin prick or blood tests, if an allergy is suspected
• a skin biopsy, in the rare cases where inflamed blood vessels (vasculitis) are suspected as the cause.

How is hives treated?

There's no surgical treatment for hives. Most cases settle with self-care or simple medicines, though longer-lasting cases sometimes need a step-by-step approach.

If you can identify what's triggering your hives, avoiding it is the best first step, whether that's a certain food, tight clothing, extreme temperatures or a particular medicine.

For symptoms that need treating, options include:

• Antihistamines: Usually the first treatment tried, available over the counter or on prescription. Non-drowsy versions are preferred, and you may need a higher dose than usual, or a combination of two to three different antihistamines, to bring symptoms under control
• Steroid tablets or menthol cream: Sometimes prescribed by a GP alongside or instead of antihistamines, particularly for short, severe episodes
• A sedating antihistamine at night: This can help if itching is disturbing your sleep
• Add-on medicines: If standard doses of antihistamines aren't enough, a doctor may add another medicine that works on the immune system, such as montelukast or, for chronic cases that don't respond to other treatment, a licensed injectable medicine called omalizumab.

Guidelines suggest antihistamine doses can be safely increased up to four times the standard licensed dose if needed, though even at this level, some people with chronic hives don't get full relief and may need to be referred to a specialist.

If you've previously had a severe allergic reaction alongside your hives, your doctor may prescribe an adrenaline auto-injector for you to carry in case of another reaction.

When should I see a doctor?

Contact a GP or call 111 if:

• your symptoms haven't improved after two days
• the rash is spreading
• hives keep coming back, as this might mean you're allergic to something
• you also have a high temperature and feel unwell
• you notice swelling underneath your skin, which could be angioedema.

Call 999 or go to A&E straight away if:

• your lips, mouth, throat or tongue suddenly swell up
• you're breathing very fast, wheezing, or struggling to breathe
• your throat feels tight or you're struggling to swallow
• your skin, tongue or lips turn blue, grey or pale
• you or someone else becomes very confused, drowsy, dizzy, or faints and doesn't wake up.

These can be signs of a serious allergic reaction (anaphylaxis) and need immediate treatment.