Urticaria also known as hives or wheals is an intense pruritis and erythematous plaques that are raised and present throughout the different parts of the body.
It is common across all ages, affecting 10-15% of people.
🔢 Classification
We can classify urticaria as either acute or chronic:
- Acute urticaria - spontaneous wheals and/or angioedema for <6 weeks.
- Chronic urticaria - urticaria that has been present continuously or intermittently for >6 weeks. It has 2 subtypes:
- Chronic spontaneous urticaria - the presence of idiopathic wheals and/or angioedema is spontaneous and lasts >6 weeks.
- Inducible urticaria - such as heat urticaria, solar urticaria, contact urticaria, cholinergic urticaria, aquagenic urticaria, symptomatic dermatographism and more subtypes which have an inducible and identifiable cause.
Pathophysiology
Urticaria is mast-cell driven. Activated mast cells and basophils are responsible for the secretion of histamine and histamine-like mediators that cause itchiness on the superficial dermis as well as vasodilation → angioedema of the deep dermis. Swelling that leads to laryngeal oedema needs to be treated promptly due to the life-threatening risk of airway obstruction.
Histamine release is triggered by:
- Allergy
These are type 1 hypersensitivity reactions mediate by IgE. The agents that mediate these reactions could be:
- Food
- Medication
- Latex
- Insects
- Infection
- Physical disease (inducible urticaria) - as mentioned above.
- Systemic disease - precedes illness such as SLE and RA but this is less common.
- Chronic spontaneous urticaria - this makes up 90% of cases if chronic urticaria and is most likely due to some autoimmune phenomenon.
😷 Presentation
- Erythematous, pruritic, raised, blanching wheals on the superficial dermis. They may be small, large, oval-shaped or annular and take up to 24 hours to disappear.
- Angioedema - swelling around lips and eyes.
🔍 Investigations
A history should be taken to identify the trigger and a skin prick test may also aid diagnosis.
🧰 Management
- 🥇 Identification of trigger and avoidance of trigger
- 🥇 Non-sedating antihistamines
- Cetirizine
- For severe or refractory episodes → prednisolone