Hives

The wheals can vary in size, from relatively small to as large as a dinner plate. The wheals may be circular, oval or annular (ring-shaped).

Hives can affect any part of the body, but is common on the torso, throat, arms and legs. The wheals generally appear in clusters, with one cluster getting worse as another gets better. Most wheals disappear without a trace within a few hours, only to be replaced by a new one elsewhere on the skin.

Wheals that persist in exactly the same spot for more than 24 hours may indicate a different disorder known as urticarial vasculitis. In acute (short-lived) hives, the wheals may come and go for a few days or weeks. In rare cases of chronic hives, wheals may persist for more than 6 weeks.

The wheals come and go for months or even years. It is thought that around one in every 6 people will experience an attack of acute hives at some point in their lives. In most people this is not due to allergy.

Underneath the lining of the skin, gut, lungs, nose and eyes are mast cells.

These are designed to kill worms and parasites

Mast cells contain chemicals including histamine

When these are released into the skin in small amounts, they cause itching and irritation.

When large amounts are released into the skin, fluid leaks out of blood vessels, resulting in swelling of the skin (hives). Occasionally, hives produce swelling without an itch.

Symptoms of hives include:

• raised circular wheals that look like mosquito bites – these are red on the outer rim
• white in the centre
• each wheal lasts for around 2 to 4 hours (rarely up to 24 hours). Wheals appear in batches or clusters
• as one batch fades away a new batch appears with chronic hives
• the rash may persist for months to years
• occasionally decades

In 80% of cases the cause of hives is unknown.

Some factors known to cause hives include:

• In chronic hives it is rare to find a cause although aspirin
• codeine may aggravate it. If a trigger is identified
• it is possible to avoid that trigger
• then the hives will resolve. Where no trigger is found
• or the trigger cannot be avoided treatment may include avoidance of factors that make the condition worse – such as aspirin
• codeine sunshine heat
• hot showers antihistamines – some people require 2
• or even 4 tablets a day to control hives

These are available from pharmacies without prescription

Some antihistamines cause drowsiness

For chronic hives, there are a number of other medications that can be prescribed. About hives Hives (urticaria) Mast cells and histamines Symptoms of hives localised itching with acute urticaria, the rash may last for days or weeks Causes of hives medication – such as antibiotics, aspirin and codeine allergic reactions to foods some food additives infections – including bacterial, viral or parasitic respiratory infections (particularly in young children) certain underlying conditions – such as systemic lupus erythematosus, rubella and hepatitis emotional stress contact with plants or animals heat cold temperatures exercise and sweating bee and wasp stings Treatment for hives Where to get help Your GP (doctor) Dermatologist American Society of Clinical Immunology and Allergy (ASCIA) – Locate a specialist .

Key Points

• are common skin rashes characterised by one or many wheals (lumps) of reddened, raised and itching skin
• Hives can affect any part of the body, but is common on the torso, throat, arms and legs
• When these are released into the skin in small amounts, they cause itching and irritation
• In 80% of cases the cause of hives is unknown
• Some antihistamines cause drowsiness