Hives (urticaria) is a common skin rash characterised by one or many wheals of reddened, raised and itching skin. The weals can vary in size, from relatively small to as large as a dinner plate. The weals may be circular, oval shaped or annular. The condition can afflict any part of the body, but is common to the trunk, throat, arms and legs. The weals generally rise in clusters, with one cluster getting worse as another gets better.

Most weals disappear without a trace within a few hours only to be replaced by a new one elsewhere on the skin.  Weals that persist in exactly the same spot for more than 24 hours may indicate a different disorder known as urticarial vasculitis.

In acute urticaria, the weals may come and go for a few days or weeks.  Rarely do they persist for more than 6 weeks. Chronic urticaria is much less common.  In chronic urticaria, the weals come and go for months or even years.

It is thought that around one in every six people will experience at least one attack of acute urticaria at some point in their lives.

Acute urticaria can be triggered by a number of different factors. Common causes include respiratory infections (particularly in young children), contact with animals or plants, allergic reactions to foods or medications (particularly pain killers and antibiotics), and sometimes insect stings and food additives or preservatives.

In chronic urticaria, it is rare to find a cause, although aspirin and codeine may aggravate chronic urticaria.

Symptoms of hives

Symptoms of hives include:

  • Raised circular weals appear that look like mosquito bites.
  • The weals are red on the outer rim and white in the centre.
  • Localised itching is usually present.
  • An individual weal has a lifespan of around 2-4 hours. Rarely up to 24 hours.
  • The weals appear in batches or clusters.
  • One batch fades away as a new batch appears.
  • In acute urticarial, the rash may last for days or weeks.
  • Inn chronic urticarial the rash may persist for months to years, occasionally decades

Mast cells and histamines

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 chemicals including histamine. When these are released into the skin, they cause itch, irritation and fluid to leak out of blood vessels, resulting in swelling of the skin. Occasionally, hives produce swelling without itch.

Causes of hives

In over two third of cases, the cause of hives is unknown. Some factors known to cause hives include:

  • medications – such as antibiotics, aspirin and codeine
  • some food additives
  • infections – including bacterial, viral or parasitic
  • certain underlying conditions – such as systemic lupus erythematosus, rubella and hepatitis
  • contact with plants or animals
  • sunshine and heat
  • cold temperatures
  • exercise and sweating
  • bee and wasp stings.

Treatment for hives

If a trigger is identified and 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 exacerbate the condition – such as aspirin, codeine, sunshine, heat and hot showers.
  • Some people require 2, 3 or even 4 tablets a day to control hives.  These are available from pharmacies without prescription.  Some antihistamines cause drowsiness.
  • For chronic urticarial there are a number of other medications that can be prescribed to control hives.

New research into urticaria

Two new treatments are currently being tested in clinical trials in Australia.  Both agents belong to a class of medicines called biologic therapies.  Both agents target igE mediated release of histamine from mast cells in the skin. People interested in participating in clinical trials should visit our clinical trials page: www.sinclairdermatology.com.au/clinical-trials

Things to remember

  • Hives is a skin rash characterised by reddened and raised circular weals.
  • This type of skin rash is an allergic reaction, which means the immune system responds to a substance.
  • Treatment options include avoidance of known triggers, and medications such as antihistamines.

To book a consultation please call us on 9654 2426 or email appointments@sinclairdermatology.com.au

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