Hives

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.

Read more about the symptoms of 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 
• infection
• 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
• emotional stress
• warm temperature

Read more about the causes of urticaria.

Diagnosing urticaria

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.

Read more about diagnosing urticaria.

Treating urticaria

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 called antihistamine 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.

Read about treating urticaria.

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.

Read about the complications of urticaria.