Urticaria (hives)

Updated March 2025

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What is urticaria?

Urticaria, commonly known as hives, are pink or red rashes that look like lumps (wheals) or blotches on the skin. Sometimes, they look like mosquito bites. They are often very itchy.

Urticaria occurs when mast cells (type of immune cell) in the skin release chemicals, such as histamine. These chemicals cause small blood vessels in the skin to leak fluid, resulting in lumps/wheals forming. The chemicals can also make the skin around the wheal red and feel itchy.

Up to 20% of people may have urticaria at some time during their lives, and in most cases, urticaria is not due to an allergic reaction.

What does urticaria look like?

It is important to understand that urticaria can look the same no matter the cause. Urticaria caused by an infection can look the same as urticaria caused by an allergic reaction. Being aware of what was going on at the time the urticaria appeared and how long it lasted may help doctors decide the possible cause.

Urticaria can look like a mosquito bite but can also come in all different shapes and sizes. Wheals can be as small as a pinhead (a few millimetres) or as large as a dinner plate (several centimetres). The wheals may be round, oval rings, or patches and can change as the rash develops. The wheals are often white or pale in colour surrounded by red skin (flare) around the lump.

Some people might have only a few wheals on one part of their body, while others can have hundreds all over.

View photos of what urticaria looks like.

How long does urticaria last?

Urticaria can last minutes to hours and sometimes even days to weeks. The length of the urticaria depends on the type.

Types and causes of urticaria

Acute urticaria

Urticaria due to allergic reactions:

• Urticaria can be a sign of a mild to moderate allergic reaction to food, insects, medicines or other allergens.
• Urticaria due to allergy will usually appear within 2 hours of being exposed to the allergen.
• Urticaria alone is not life-threatening. On the ASCIA Action Plan for Anaphylaxis or Allergic Reactions, hives/welts are listed as a sign of a mild to moderate allergic reactions. However, if you experience other signs such as swelling of the tongue or throat, breathing difficulty or dizziness at the same time as hives, this means you are experiencing anaphylaxis, and you should follow the steps on your ASCIA Action Plan to treat anaphylaxis. If there are signs of anaphylaxis, treat it as an emergency.

Chronic urticaria

There are two types of chronic urticaria:

• Chronic spontaneous urticaria: Wheals appear without an obvious cause on most days of the week for six weeks or more. The wheals may come and go and can appear anywhere on the body. There may also be swelling or angioedema.
• Physical urticaria: Wheals are caused by a known physical cause. This may include scratching or friction (dermographism), cold (cold urticaria), sunlight (solar urticaria), increased body heat (cholinergic urticaria), pressure (delayed pressure urticaria) or vibration. People with physical urticaria do not react to all the causes listed; often, they only react to one.

Note: Urticaria from cold can be severe, especially when swimming in cold water. Some people have been known to have symptoms of anaphylaxis due to cold urticaria.

People with chronic urticaria should be under the care of a doctor with specialist knowledge of this condition.

Management of urticaria

Follow specific management advice from your doctor. However, general management of urticaria includes:

• Cool, wet cloths put on the affected skin may help to reduce itch and discomfort.
• Non-drowsy antihistamines are a good treatment for urticaria. They won’t cure urticaria, but they help to lessen the severity and itch. People with chronic urticaria may be recommended by their doctor to use them to help reduce symptoms that occur frequently. Sometimes, the doctor advises using a dose much larger than the regular dose. Read more about antihistamines.
  • Note: If antihistamines do not work, you should speak to your doctor
• Severe chronic urticaria sometimes requires medicine that reduces inflammation, called immune modulators, immunosuppressive medications, or steroids.
• Special diets are not usually recommended for treating chronic urticaria. Unfortunately, it is difficult to tell who will respond to diet-based treatment. A short-term elimination diet under close medical supervision, followed by food challenges, may be helpful in a small number of adults.
• For acute urticaria caused by allergy, avoid known allergen triggers.

When to seek help

See a doctor soon

Urticaria alone does not make you sick; it is just itchy and uncomfortable. If you have urticaria and are sick with a high fever, weight loss, sore joints, or bruising, see your doctor as soon as possible. Sometimes, blood tests will be recommended to exclude other diseases.

Mental health

Chronic urticaria can affect quality-of-life and the ability to participate in everyday activities. Speak with your doctor (this could be your GP or specialist) about how your condition is affecting your mental health and seek help if needed. You may wish to call the National Allergy Helpline at Allergy & Australia to speak with an allergy educator.

For urgent 24-hour mental health support:

• If a life is in danger – call triple zero (000)
• Lifeline Australia – 13 11 14 – Crisis Support. Suicide Prevention
• Mental health helplines | Healthdirect