Hives

hives; allergy; rash; reaction; skin; itch; histamine; antihistamine; urticaria ;

Contents

• What are hives like?
• What causes hives?
• Treatment for hives
• Finding out the cause
• Other problems
• Reference

Hives, which is also called urticaria, is a very itchy rash. It is sometimes caused by allergy to something (such as some foods), but often no cause is found. Many people get hives at some time in their life, but only a few have major trouble with it.

WARNING
Sometimes when a person gets hives on the skin, there are other effects inside the body such as swelling of the tongue and upper airways which can cause breathing difficulties. This difficulty with breathing can be life-threatening for a few people, and that person needs urgent medical attention. This is called Anaphylaxis. (For more information have a look at the topic called Anaphylaxis.)

What are hives like?

• The rash of hives can be anywhere on the body, but it is often on the face, chest, abdomen and back.
• The rash consists of raised patches which can vary in size from very small (like a small insect bite) to very large (20 or more centimetres across). Some patches will merge with others to make larger patches. The patches are called 'wheals'.
• The patches may be round or quite wavy in shape. (The edges are called 'serpiginous' or 'snake like').
• The edge of each patch is red and thickened, but the middle of the patches can be red like the edges, lighter red or quite pale.
• The patches are usually very itchy.
• The patches come and go. They may last for an hour or so, but often last for a day or more. When they go the skin where the patch was is quite normal.
• The rash often comes in waves. Many patches can appear, then fade, then be replaced by new patches which may be in different places.
• A few people get hives which last for many weeks (chronic urticaria) and this might be the sign of some underlying illness.

What causes hives?

• Hives can caused by an allergic reaction to many things such as:
  • foods (some fruits such as strawberries, shellfish, peanuts, tomatoes, cheese and other milk products, soybeans, wheat)
  • exposure to moulds or animals
  • bee stings and ant bites.
• Hives can also be caused in a few people by:
  • Infections caused by bacteria, parasites, protozoa and yeasts, and other infections such as hepatitis, glandular fever (mononucleosis) and rubella (German measles).
  • Chemicals - those which can cause hives include aspirin, antibiotics such as penicillin, codeine and some food additives.
  • Exposure to heat (having a fever or a hot bath) or cold (such as exposure to ice) or sunshine.
  • Exercise
  • Pressure on the skin
  • Vibration (such as using power tools).
• Many times a cause is not found, and this is called 'idiopathic' urticaria.

Treatment for hives

• Most people do not need treatment for hives, apart from some relief from the itching.
• Antihistamines can reduce the itching, as do various lotions or creams which can be obtained from a pharmacist.
• Avoiding some things which can make the rash worse may be helpful, eg avoiding excessive heat, spicy foods, alcohol and aspirin. (Note: Aspirin should never be given to children because it can trigger a severe illness called Reye's Syndrome).
• If the rash and allergic reaction is severe, oral corticosteroids may be prescribed by a doctor.
• If there are breathing difficulties, seek urgent medical attention.

Finding out the cause

• Most people do not need tests to work out the cause of their hives because mostly the rash goes in a few days and there is not an ongoing problem.
• Sometimes it is fairly easy to work out what may have caused hives from checking what the person has been exposed to, but it can be difficult because the rash may not appear for hours or even days after the exposure.
• Skin testing for allergies might be useful if the person has hives often.
• If a food is thought to be the cause of hives that keep coming back, an 'elimination diet' may be tried. All foods which commonly cause reactions are cut out of the diet for a period (to see if the rash goes), and then possible causes are introduced in small amounts to see if a reaction happens. This needs to be done with the help of an allergy specialist or a dietitian.
• Other possible causes such as infections and other illnesses also need to be thought about, and testing done if it seems like they may be the cause.

Other problems

• As well as sometimes causing breathing difficulties, the substance causing hives may also cause swelling in the intestinal tract which can cause abdominal pain.

Reference

Australian Society of Clinical Immunology and Allergy (ASCIA)
http://www.allergy.org.au

The information on this site should not be used as an alternative to professional care. If you have a particular problem, see a doctor, or ring the Parent Helpline on 1300 364 100 (local call cost from anywhere in South Australia).

This topic may use 'he' and 'she' in turn - please change to suit your
child's sex.