Urticaria

Overview

•Wheals (hives) - raised, pale, oedematous plaques with surrounding erythematous flare; intensely itchy

•Transient and migratory - individual lesions resolve within 24 hours, leaving no skin change

•Common triggers - insect stings, foods (nuts, shellfish), NSAIDs, aspirin, ACE inhibitors, antibiotics, viral infections

•Angio-oedema - deeper swelling of lips, tongue, eyelids; airway involvement is a red flag

⚠️

A weal persisting >24 hours, painful rather than itchy, or leaving bruising suggests vasculitic urticaria - refer to dermatology; do not manage as standard urticaria.

Differential diagnosis

Key differentials

Feature	Urticaria	Cellulitis	Anaphylaxis
Itch	Intense	Not itchy	May be present
Tenderness	Non-tender	Warm and tender	Variable
Duration	Lesions resolve <24 h	Does not migrate	Rapid onset
Systemic features	None (in isolated urticaria)	May have fever	Hypotension, bronchospasm, stridor
Treatment	Non-sedating antihistamine	Flucloxacillin	IM adrenaline

Management

🥇 First-line

•loratadine or cetirizine (non-sedating H1-antihistamines) - daily for up to 6 weeks in acute urticaria; safe in asthma

🥈 Second-line

•increase non-sedating antihistamine up to four times the licensed dose (off-label)

•Add-on for sleep disturbance: chlorphenamine (sedating) at night only - not first-line or daytime monotherapy

•Severe acute episodes: add prednisolone 40 mg orally for up to 7 days alongside antihistamines, not instead of them

•Third-line (secondary care): omalizumab (anti-IgE) or ciclosporin for chronic spontaneous urticaria unresponsive to antihistamines

🎯

Loratadine and cetirizine are non-sedating and first-line. Chlorphenamine is sedating - appropriate at night as an adjunct only, never as first-line monotherapy.