The Australasian Society of Clinical Immunology and Allergy

Urticaria is commonly referred to as hives, which are weal like swellings on the surface of the skin that look like mosquito bites. They range from the size of a pinhead to that of a dinner plate. Although some unlucky individuals can have them every day for weeks, individual lumps usually disappear within minutes to hours. In most people hives are not due to allergy.

Hives are common

Approximately 1 in 6 people will develop hives some time during their life and are most common in children. Although some unlucky individuals can have them every day for weeks, individual lumps usually go in minutes to hours. In most people, hives are not due to allergy. Hives may reappear following infection, when under stress or for no particular reason.

Hives occur in the skin

Underneath the lining of the skin, gut, lungs, nose and eyes are mast cells. These are designed to kill worms and parasites. Mast cells are like land-mines, and contain bags filled with irritant chemicals including histamine. When these are released in small amounts, they cause local itch and irritation. In larger amounts, they will cause fluid to leak out of blood vessels, resulting in swelling of the skin. Occasionally, hives may not be itchy at all.

Can hives occur anywhere else?

Hives cause swellings on the surface of the skin, including the face and lips. Although these can be uncomfortable and cosmetically embarrassing, they are not dangerous. However around 1 in 3 people with hives will also have swelling of the tongue and throat, known as angioedema. Since this can cause difficulty breathing, urgent medical treatment is required.  Information on angioedema is available on the ASCIA website www.allergy.org.au/content/view/177/278/

Hives are rarely due to a nasty underlying disease

Common causes of hives include infection (particularly in young children), contact with animals or plants and allergic reactions to food, antibiotics or pain killers (such as aspirin and arthritis tablets). Sometimes insect stings, food additives or preservatives can also trigger hives. Stress can make established symptoms worse, but is a very rare cause of hives.

Most people with hives do not need tests

Tests are sometimes done when hives go on for long periods or when unusual symptoms are occurring around the same time. This is to exclude other diseases, which may appear as hives first and other conditions later. Allergy testing is performed when the history suggests of an allergic cause.

Treatment of hives

• Time is a wonderful healer. Most hives resolve within a couple of weeks.
• Avoid aggravating factors Non-specific measures such as avoiding excessive heat, spicy foods or alcohol are often useful.
• Aspirin should also be avoided as it often makes symptoms worse.
• Medicines like antihistamines are often used to reduce the severity of the itch. Severe throat swelling requires early use of medication and attention by your doctor or in hospital. Other medicines (like cortisone tablets) may be needed if symptoms are severe.
• Special diets Occasionally, going on a restricted diet will help. Unfortunately, one cannot predict who will or will not respond to diet on the basis of history or allergy testing. The only way to sort it out is to put people on a temporary elimination diet under close supervision, followed by challenges if it helps.

© ASCIA 2010

The Australasian Society of Clinical Immunology and Allergy (ASCIA) is the peak professional body of Clinical Immunologists and Allergists in Australia and New Zealand.

Website: www.allergy.org.au

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Disclaimer

This document has been developed and peer reviewed by ASCIA members and is based on expert opinion and the available published literature at the time of review.  Information contained in this document is not intended to replace medical advice and any questions regarding a medical diagnosis or treatment should be directed to a medical practitioner. The development of this document is not funded by any commercial sources and is not influenced by commercial organisations.

Content last updated June 2010