(Also called hives)

They are small itchy lumps that appear on the skin. They may be associated with a patchy erythematous rash. This can be localised to a specific area or widespread. They may be associated with angioedema and flushing of the skin.

Pathophysiology

Urticaria are caused the release of histamine and other pro inflammatory chemicals by mast cells degranulation.

This may be part of an allergic reaction in acute urticaria (IgE) or an autoimmune reaction in chronic idiopathic urticaria.

Causes

Acute urticaria:

• Allergies to food, medications or animals
• Contact with chemicals, latex or stinging nettles
• Medications - aspirin, penicillins, NSAIDs, opiates
• Viral infections
• Insect bites
• Dermatographism (rubbing of the skin)

Chronic urticaria, 3 types:

• Chronic idiopathic urticaria - recurrent episodes with no clear cause
• Chronic inducible urticaria - Induced by certain triggers:
  • Sunlight
  • temp change
  • exercise
  • strong emotions
  • Hot or cold weather
  • pressure
• Autoimmune urticaria - Associated with an underlying autoimmune condition e.g. SLE