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Chronic Spontaneous Urticaria (CSU)

Frequently Asked Questions

This document has been developed by ASCIA, the peak professional body of clinical immunology/allergy specialists in Australia and New Zealand. ASCIA information is based on published literature and expert review, is not influenced by commercial organisations and is not intended to replace medical advice.         

For patient or carer support contact Allergy & Anaphylaxis Australia or Allergy New Zealand.

pdfASCIA PC Chronic Urticaria FAQ 2024128.75 KB

Q 1: What is chronic spontaneous urticaria?

Chronic spontaneous urticaria (CSU) is the name for hives (urticaria) that are chronic, lasting six weeks or more, three to four times per week, and have no known cause (spontaneous).

Symptoms of CSU can be like other types of hives, which:

  • Are red, white, or skin coloured itchy blotches or lumps, and often mistaken for mosquito bites.
  • Vary in size - they can be as small as the head of a pin, or as large as a dinner plate.
  • Can occur on any part of the body.
  • Usually last less than 24 hours, but then reappear soon after on a different part of the body.

Some people with CSU may also develop angioedema, a condition that causes swelling in different parts of the body (commonly the face, lips, tongue, throat, and genital area) that may last several days.

Q 2: What causes hives?

One in five people will get hives at some time during their life and there are several causes:

  • Hives occur when histamines are released from cells which are found in the lining of the skin and other body organs.
  • The release of histamine makes the skin itch, and causes blood vessels to expand and leak fluid, causing redness and swelling.
  • Hives may be caused by infections, or contact allergy to plants or animals.
  • Hives can be part of an allergic reaction, but hives that last for more than a few days are usually not caused by allergy.

CSU is sometimes the result of an underlying medical condition but in most cases the cause is not known (idiopathic).

Q 3: How is chronic spontaneous urticaria diagnosed?

CSU is diagnosed when a person develops hives lasting for more than six weeks, without an allergic cause. To confirm this diagnosis, your doctor will:

  • Review medical history and give a physical examination. Keeping a diary of symptoms with a photographic record of hives can be very helpful for this.
  • Order blood tests if an underlying condition is suspected. Allergy tests are usually not required unless there is a reason to suspect an allergic cause.

Q 4: How is chronic spontaneous urticaria treated?

The goal of treatment for chronic spontaneous urticaria (CSU) is to reduce or stop the itch and stop the hives developing with as few side effects as possible. Most cases of CSU will get better within a few weeks without any treatment but in some cases, they can last for many months or even longer.

Common treatment options for CSU include:

  • Non-drowsy antihistamines are often used to relieve the itch that comes with hives. Higher than standard doses may be required to achieve this for people with CSU.
  • People with severe CSU symptoms affecting quality of life, who do not respond to simple treatments may need to be referred to a clinical immunology/allergy specialist. They will be assessed, and options for long term treatment discussed:
  • Immune modulators – usually given as subcutaneous (under the skin) injections that can be given at home.
  • Immunosuppressive medications – corticosteroids can be used to treat severe symptoms for a short time.

© ASCIA 2024

Content updated June 2024

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