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.
Long-term urticaria is much less common and affects around 1 in 1,000 people in England. Women are twice as likely to develop chronic urticaria than men.
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.