GPAtlas🧭 When to suspect
Suspect urticaria when a patient presents with transient, intensely itchy, raised erythematous wheals (hives) that can appear anywhere on the body.
The defining feature is timing:
• Each individual wheal blanches, migrates and resolves within <24 hours, leaving no mark.
• The overall eruption may still come and go for weeks.
It is frequently accompanied by angioedema – deeper, non-pitting swelling of skin or mucosa.
Classify by duration and trigger, recognise the dangerous mimics (urticarial vasculitis and bradykinin-mediated angioedema), and remember that the great majority of long-lasting urticaria is not an allergy.
| Pattern | Defining feature |
|---|---|
| Acute urticaria | • Wheals ± angioedema for <6 weeks • Usually post-viral, drug-related or idiopathic, and typically self-limiting |
| Chronic spontaneous urticaria (CSU) | • Wheals on most days for ≥6 weeks with no consistent external trigger • Frequently autoimmune • Waxes and wanes over months to years |
| Chronic inducible urticaria (CIndU) | Reproducibly provoked by a physical stimulus – dermographism, cold, heat, delayed pressure, cholinergic (sweating/exercise), solar or aquagenic. |
| Urticaria with angioedema | • Deeper swelling of soft tissues (lips, eyelids, tongue) accompanying wheals • Seen in up to ~40% of CSU |
| Angioedema without wheals | Swelling alone – think ACE-inhibitor-induced or hereditary/acquired C1-inhibitor deficiency: a different, bradykinin-mediated pathway. |
|
🧠 Clinical pearl • Treat angioedema without wheals as a separate disease. • It is usually bradykinin-mediated, not histaminergic. • Antihistamines, steroids and adrenaline are therefore largely ineffective. • ACE-inhibitor angioedema can appear months to years into stable therapy. • Recurrent attacks without urticaria should prompt C1-inhibitor testing for hereditary angioedema. |
Source: British Association of Dermatologists · DermNet
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