What is urticaria?
Urticaria is a type of skin rash that has raised lumps (“wheals”) that can be itchy. It is due to the release of chemicals such as histamine from cells in the skin called mast cells. The wheals can be a few millimetres or several centimetres in size, coloured white or red. The wheals can come on and spread to any part of the body very quickly, sometimes within minutes. Each wheal may last a few minutes or several hours, and may change shape. Urticaria can happen at the same time as swelling of parts of the body such as the hands, feet, lips or around the eyes. This swelling is called angioedema.
Does urticaria have any other names?
Yes. The common name is hives.
How common are hives?
Hives are very common, affecting 2-3% of children. Most cases only last for a few days or weeks and get better without any treatment.
How long do hives last?
Hives often come and go over several hours, but can keep doing this for days or weeks. This is called acute hives. Sometimes hives will keep coming back for more than 6-8 weeks, and this is called chronic hives.
What is the relation between hives and allergy?
Most cases of hives are NOT due to allergy and allergy tests are rarely helpful in finding a cause.
Acute hives can be due to a viral illness or less commonly an allergy to medicines (often antibiotics or rarely food). If hives are due to an allergy there will be a link between having the medicine or food, and the hives starting in 1-2 hours. Hives due to allergy can be itchy. The most common cause of hives is an infection (often a virus, e.g. a common cold) which occurred 1-2 weeks earlier. This is called post-infectious urticaria. Your child may not appear sick at the time of the hives. Sometimes there is no obvious cause for the hives.
Chronic hives are not due to an allergy. Usually a cause cannot be found and this is called Chronic Idiopathic Urticaria (CIU). Rarely, chronic hives can be due to autoimmune disease (an immune reaction to oneself), and may be linked with other autoimmune conditions (e.g. thyroid disorder).
Are there any other types of hives?
Yes, physical urticaria refers to hives caused by outside physical factors. The wheals usually take about 5-10 minutes to develop, and last 30 to 60 minutes. Triggers of physical urticaria can include pressure (stroking the skin), sweating, heat, cold and sunlight. Some people suffer from a mixture of different types of physical urticaria.
Do tests need to be done?
In most cases of acute hives, allergy tests are not helpful and don’t need to be done. Sometimes your doctor may order blood tests, mainly in cases of chronic hives.
What is the treatment for hives?
Treatment depends on the type of hives and your child’s history.
The most common treatment is oral antihistamines. These medicines reduce the number of wheals for most children with hives. Antihistamines are safe to use on a regular basis, but you should discuss this with your doctor. Chronic hives do not always respond well to antihistamine therapy.
Rarely, some cases of hives do not respond to the above treatment and other medications are used. This would be as directed by an Immunologist/Allergist or Dermatologist.
In addition to drug treatment there are some general measures to follow. Do not take the medications your doctor has told you to avoid. In some cases aspirin, codeine and non steroidal anti-inflammatory drugs (for example ibuprofen) may make the hives worse. It is usually safe to take paracetamol.
Does dietary treatment have a role?
Dietary treatment is not necessary or helpful for acute hives.
A small proportion of cases of chronic hives are improved by the removal of colourings, preservatives and salicylates from the diet. This should only be done in consultation with your Immunologist/Allergist and a dietician.
What if my child developed hives when taking antibiotics?
Many cases of hives that occur at the same time as taking antibiotic ingestion are due to the infection rather than an allergy to the antibiotic. An antibiotic ‘challenge’ under observation is needed to diagnose an antibiotic allergy.
Where can I find more information on the Internet?
- The Australian Society of Clinical Immunology and Allergy (ASCIA) website contains useful information on hives written by Australian specialists: www.allergy.org.au.
- DermNet NZ the web site of the New Zealand Dermatological Society has information about allergic skin diseases and hives: www.dermnetnz.org