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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Individual wheals last <24 hours, blanch with pressure. Acute (<6 weeks) vs chronic (>=6 weeks)
- First-line: non-sedating H1 antihistamine (cetirizine 10 mg OD or fexofenadine 180 mg OD)
- Chronic: up-dose to 4x if needed, then specialist referral for omalizumab
- ACE inhibitor angioedema: STOP ACE inhibitor. Bradykinin-mediated — antihistamines/adrenaline do NOT work
- Hereditary angioedema (C1-esterase inhibitor deficiency): treat with C1-INH concentrate or icatibant
Overview
Urticaria results from mast cell degranulation releasing histamine causing vasodilation and increased permeability. Individual wheals last <24 hours. Angioedema involves deeper swelling. Classified as acute (<6 weeks) or chronic (>=6 weeks). Chronic spontaneous urticaria affects ~1% of the population. Hereditary angioedema (HAE) is a separate entity due to C1-esterase inhibitor deficiency — does NOT respond to standard treatment.
Epidemiology
Acute urticaria affects ~15-25% of people at some point. Most is idiopathic or viral-triggered. ACE inhibitor angioedema occurs in ~0.1-0.7% of users. HAE is rare (~1 in 50,000), autosomal dominant.
Clinical Features
Symptoms
Itchy raised wheals lasting <24 hours each — migratory
Deeper swelling of lips, eyelids, tongue (angioedema)
Stridor, hoarse voice, respiratory distress (airway angioedema)
Anaphylaxis features (urticaria + hypotension + bronchospasm)
Signs
Raised, erythematous, blanching wheals
Dermographism: wheals at sites of skin stroking
Soft tissue swelling of lips, periorbital area
Lesions persisting >24 hours or leaving bruising — consider urticarial vasculitis
Tongue/laryngeal swelling causing airway compromise
Investigations
First-line
Clinical diagnosisAcute urticaria — no routine investigations needed
Second-line
FBC, ESR, CRP, TFTsFor chronic urticaria (>=6 weeks)
C4 levelIf recurrent angioedema without urticaria — LOW in HAE (screening test)
Specialist
C1-esterase inhibitor level/functionConfirmatory for HAE if C4 low
Skin biopsyIf urticarial vasculitis suspected (wheals >24 hours, bruising)
1
Acute urticaria
- Identify and avoid triggers
- Non-sedating H1 antihistamine: cetirizine 10 mg OD or fexofenadine 180 mg OD
- Short course prednisolone 40 mg for 3-5 days if severe
- If anaphylaxis: IM adrenaline per protocol
2
Chronic spontaneous urticaria
- First-line: non-sedating H1 antihistamine at standard dose
- If inadequate: up-dose to 4x (e.g. cetirizine 10 mg QDS)
- If still inadequate: specialist — omalizumab (anti-IgE, NICE TA339) or ciclosporin
3
ACE inhibitor angioedema
- STOP ACE inhibitor immediately — do NOT rechallenge
- Switch to ARB (very low cross-reactivity)
- Bradykinin-mediated — antihistamines and adrenaline do NOT work
4
Hereditary angioedema
- Does NOT respond to antihistamines, steroids, or adrenaline
- Acute: IV C1-esterase inhibitor concentrate or icatibant
- Prophylaxis: danazol, tranexamic acid, or C1-INH replacement
Complications
- Anaphylaxis: Medical emergency
- Airway compromise: Laryngeal angioedema
- Quality of life: Chronic urticaria significantly impacts sleep and work
UKMLA Exam Tips
- 1Wheals <24 hours = urticaria. Wheals >24 hours + bruising = urticarial vasculitis — biopsy needed
- 2ACE inhibitor angioedema: BRADYKININ-mediated — antihistamines/adrenaline do NOT work
- 3HAE: recurrent angioedema WITHOUT urticaria + family history + low C4 + low C1-esterase inhibitor
- 4Up-dosing antihistamines to 4x is standard step-up for chronic urticaria
- 5Omalizumab (anti-IgE) is the biologic for refractory chronic spontaneous urticaria
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regional clinical guidance
Urticaria and Angioedema: guidance by region
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