Synopsis
Diagnose wheal-based acute and chronic spontaneous urticaria, identify anaphylaxis and alternative inflammatory disease, investigate selectively, and use a safe stepwise antihistamine strategy.
- A wheal is raised, itchy and transient; an individual ordinary urticarial lesion resolves within twenty-four hours, although new wheals can appear elsewhere.
- Acute urticaria lasts up to six weeks; recurrent wheals on most days beyond six weeks define chronic urticaria and require phenotype-led review.
- Chronic spontaneous urticaria is usually not caused by an external allergen, so routine broad food panels and restrictive diets are unhelpful.
Key red flags
Airway swelling, wheeze, hypoxia, hypotension, syncope, severe abdominal symptoms after an allergen, fever, bruising, painful fixed lesions or systemic illness require urgent reassessment.
Eyelid or lip angioedema accompanying wheals supports mast-cell disease, but tongue or laryngeal symptoms demand immediate ABC assessment.
Investigation priorities
Confirm that individual lesions are transient wheals rather than a fixed exanthem.
Management branches
Wheals or angioedema occur with airway, breathing or circulation compromise or rapidly progressive systemic symptoms.
- Call for help, lie the patient flat with legs raised unless breathing requires a supported sitting position, and do not allow standing or walking.
- Give intramuscular adrenaline in the anterolateral thigh and repeat after five minutes when life-threatening features persist while providing oxygen and monitoring.
Key medicines
Cetirizine 10 mg tabletsAdults and adolescents aged 12 years and over take 10 mg orally once daily; reduce according to renal function and the product information.
Fexofenadine 180 mg tabletsAdults and children aged 12 years and over take 180 mg orally once daily before a meal for chronic idiopathic urticaria.