What is hives?

Hives (also known as 'urticaria' or 'nettle rash'), is a skin rash that can be triggered by a variety of things including allergic reactions, medicines or an infection. Sometimes the trigger is unknown.

What are the symptoms of hives?

The common symptoms include itchy, raised red or skin-coloured bumps or welts on the skin. The raised areas of skin are known as wheals, which often fade after a few hours but can sometimes reappear elsewhere on the body.

The hives rash can last for a few minutes to hours, and usually disappears within 24 hours.

Sometimes people get hives on most days. This is called chronic urticaria. See your doctor if you have hives that keep coming back.

What causes hives?

The hives rash is caused when the body produces a substance called histamine, which is a protein used to fight off viruses and bacteria.

In most cases, it is not known what triggers this reaction. Sometimes the hives rash happens because of:

• an infection
• immune system disease
• an insect sting or bite
• touching an animal or plant you are allergic to
• allergy to food or medication
• having a dye injected during a radiological test

In some people, hives may be caused by cold air or water, heat, sunlight, vibration, scratching, exercise, sweating, stress, spicy food, alcohol or coffee.

In children, a virus is the most common cause of hives.

Hives that last for days at a time are almost never due to an allergy, apart from an allergy to a specific medication.

Stress rarely causes hives, but stress can make the symptoms worse.

How are hives treated?

No treatment is normally needed. However, if the hives rash continues or gets worse, it can be treated by taking antihistamines. You can buy antihistamines over-the-counter at pharmacies. If these do not control the symptoms, talk to your doctor about stronger medication.

Sometimes hives can last for a long time. If you have hives for more than 6 weeks you might need more tests to identify whether an underlying infection or chronic immune disorder is causing the symptoms.

If the hives are caused by a specific trigger such as a food or medicine, you should avoid this trigger.

If your baby gets hives repeatedly, it's important to see your doctor, as your baby may be allergic to something they are being fed frequently, such as cow's milk.