Urticaria are also known as 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. Urticaria can be classified as acute urticaria or chronic urticaria.
Pathophysiology
Urticaria are caused the release of histamine and other pro-inflammatory chemicals by mast cells in the skin. This may be part of an allergic reaction in acute urticaria or an autoimmune reaction in chronic idiopathic urticaria.
Causes of Acute Urticaria
Acute urticaria is typically triggered by something that stimulates the mast cells to release histamine. This may be:
- Allergies to food, medications or animals
- Contact with chemicals, latex or stinging nettles
- Medications
- Viral infections
- Insect bites
- Dermatographism (rubbing of the skin)
Chronic Urticaria
Chronic urticaria is an autoimmune condition, where autoantibodies target mast cells and trigger them to release histamines and other chemicals. It can be sub-classified depending on the cause:
- Chronic idiopathic urticaria
- Chronic inducible urticaria
- Autoimmune urticaria
Chronic idiopathic urticaria describes recurrent episodes of chronic urticaria without a clear underlying cause or trigger.
Chronic inducible urticaria describes episodes of chronic urticaria that can be induced by certain triggers, such as:
- Sunlight
- Temperature change
- Exercise
- Strong emotions
- Hot or cold weather
- Pressure (dermatographism)
Autoimmune urticaria describes chronic urticaria associated with an underlying autoimmune condition, such as systemic lupus erythematosus.
Management
Antihistamines are the main treatment for urticaria. Fexofenadine is usually the antihistamine of choice for chronic urticaria. Oral steroids may be considered as a short course for severe flares.
In very problematic cases referral to a specialist may be required to consider treatment with:
- Anti-leukotrienes such as montelukast
- Omalizumab, which targets IgE
- Cyclosporin
Last updated January 2020