Causes of urticaria 

Urticaria occurs when histamine and other chemicals are released from under the skin's surface, causing the tissues to swell.

Short-term (acute) urticaria 

The triggers of acute urticaria are unknown in around half of all cases.

Recognised triggers include:

  • a food allergy  to foods such as peanuts, shellfish, eggs and cheese
  • an allergic reaction  to environmental factors such as pollen, dust mites or chemicals
  • an allergic reaction to latex  which can be a common problem in healthcare workers
  • infections  which can range from relatively trivial, such as a cold, to very serious, such as HIV
  • insect bites and stings
  • emotional stress
  • certain medications that can cause urticaria as a side effect – including antibioticsnon-steroidal anti-inflammatory drugs (NSAIDs) and aspirin
  • physical triggers  such as pressure to the skin, changes in temperature, sunlight, exercise or water

Long-term (chronic) urticaria

Chronic urticaria may occur when the body's immune system attacks its own tissues. This is known as an autoimmune reaction.

About a third to half of all chronic cases of urticaria are thought to be autoimmune related.

It's not known why autoimmune urticaria develops, although it can sometimes occur in combination with other autoimmune conditions, such as:

  • rheumatoid arthritis  when the immune system attacks the joints
  • lupus  when the immune system attacks the joints and skin, and people usually feel tired all the time

Chronic urticaria can also be linked to other chronic illnesses and infections, such as:

Chronic urticaria tends to come and go. Many people find that certain things make it reappear or make existing symptoms worse. Triggers  sometimes include:

  • stress
  • alcohol
  • caffeine
  • warm temperatures
  • prolonged pressure on the skin  this can happen by wearing tight clothing
  • medications  such as NSAIDs, and the painkiller codeine
  • certain food additives  such as salicylates, which are found in tomatoes, orange juice and tea
  • insect bites and stings
  • exposure to heat, cold, pressure or water

ACE inhibitors that are often used to treat high blood pressure (hypertension) can be linked to deeper swellings of angioedema.

Page last reviewed: 28/02/2016

Next review due: 31/12/2018