Urticaria
Exam Tips
- Key discriminator: individual urticarial weals fade within 24 hours; lesions lasting >24 hours, painful, non-blanching, or leaving bruising suggest urticarial vasculitis.
- In OSCE history, ask timing versus food exposure: true IgE-mediated food allergy is usually reproducible within about 1 hour of ingestion.
- Use UAS7 language in viva answers to show severity assessment and treatment monitoring.
- Always state red flags requiring emergency action: tongue/laryngeal swelling, wheeze, hypotension, syncope.
- See figure reference: classic wheal-and-flare morphology in a dermatology atlas image of urticaria lesions (useful for spot diagnosis practice).
Definition
Urticaria is a mast cell-mediated skin disorder causing transient, pruritic, raised weals (hives) in the superficial dermis, often with surrounding erythema and central pallor. Individual lesions usually resolve within 24 hours without residual skin change; disease is classified as acute (<6 weeks) or chronic (>=6 weeks), and may occur with or without angio-oedema.
Pathophysiology
Activated cutaneous mast cells release histamine, leukotrienes, prostaglandins, cytokines, and other mediators, producing vasodilation, increased capillary permeability, sensory nerve stimulation (itch), and superficial dermal oedema (weals). In chronic spontaneous urticaria, a substantial subgroup has autoimmune disease with IgG autoantibodies to Fc epsilon RI (or IgE), lowering the threshold for mast-cell/basophil activation; complement amplification can further sustain inflammation. Chronic inducible urticaria is triggered by physical stimuli (for example cold, pressure, heat, vibration, water, cholinergic stimuli), while deeper mediator-driven oedema in subcutis/submucosa causes angio-oedema.
Risk Factors
- Female sex
- Age 20-40 years (can occur at any age)
- Atopy (especially in acute urticaria)
- Recent viral infection (common trigger, especially in children)
- Drugs: NSAIDs (including aspirin), penicillins, some vaccines
- Food allergens (for acute IgE-mediated reactions): milk, egg, peanuts, tree nuts, shellfish
- Insect stings/bites or latex/contact allergens
- Autoimmune disease (especially thyroid autoimmunity) in chronic spontaneous urticaria
- Physical triggers: cold, heat, pressure, vibration, exercise/emotion, water, light
Clinical Features
Symptoms
- Intense itch (sometimes burning)
- Recurrent transient weals, often episodic
- Possible associated angio-oedema (lips, eyelids, tongue, hands, feet, genitalia)
- Sleep disturbance and reduced quality of life in chronic disease
- Trigger-related flares (for example NSAIDs, stress, heat/cold, pressure)
Signs
- Raised erythematous or pale-centred weals of variable size and shape
- Flare around central swelling
- Lesions are fleeting; each typically resolves within 1-24 hours
- Dermographism: linear weals after stroking/scratching skin
- No residual bruising/purpura in uncomplicated urticaria
Investigations
Management
Lifestyle Modifications
- Explain benign but potentially relapsing course; provide trigger diary and avoid identifiable precipitants
- Avoid aggravating drugs (especially aspirin/NSAIDs) if they worsen symptoms
- Use loose clothing and reduce pressure/friction in delayed-pressure/dermographic disease
- For inducible urticarias, minimize specific physical triggers (cold, heat, vibration, rapid temperature shifts)
- Safety-net urgently for tongue/throat swelling, voice change, breathing difficulty, collapse (possible anaphylaxis/airway compromise)
Pharmacological Treatment
Second-generation H1 antihistamines (first line)
- Cetirizine 10 mg orally once daily
- Loratadine 10 mg orally once daily
- Fexofenadine 180 mg orally once daily
Preferred due to lower sedation burden. In refractory chronic urticaria, specialist-guided up-dosing up to 4-fold standard dose is common practice (often off-label). Warn about residual drowsiness (especially cetirizine in some patients) and driving impairment.
Short-course oral corticosteroid (selected severe flares)
- Prednisolone 20-40 mg orally once daily for up to 5-7 days
Use shortest effective course only; avoid repeated courses due to hyperglycaemia, mood change, hypertension, infection risk, and adrenal suppression with prolonged use.
Biologic for refractory chronic spontaneous urticaria (specialist use)
- Omalizumab 300 mg subcutaneously every 4 weeks
Consider after failure of high-dose second-generation antihistamines. Monitor for rare anaphylaxis post-injection; initiate in specialist allergy/dermatology pathways.
Third-line immunomodulator (specialist, off-label in many settings)
- Ciclosporin 3-5 mg/kg/day orally in divided doses
Use only with specialist monitoring. Key safety issues: nephrotoxicity, hypertension, infection risk, drug interactions, and need for renal function/BP monitoring.
If anaphylaxis is present (emergency treatment, not routine urticaria therapy)
- Adrenaline (epinephrine) 500 micrograms IM (0.5 mL of 1 mg/mL [1:1000]) in adults; repeat every 5 minutes if needed
Treat as anaphylaxis pathway with airway/breathing/circulation support and urgent transfer. Do not delay adrenaline when systemic features are present.
Complications
- Excoriations with secondary bacterial skin infection
- Post-inflammatory pigment change or scarring from persistent scratching
- Sleep disturbance and daytime fatigue
- Impaired school/work performance
- Psychological morbidity (anxiety, low mood, social withdrawal)
- Co-existing angio-oedema with potential airway compromise
- Rare progression to anaphylaxis in trigger-associated cases
Prognosis
Acute urticaria is usually self-limiting with excellent short-term outcome. In chronic spontaneous urticaria, about half of patients remit over months to a few years, but a minority have persistent disease for 10 years or longer; prognosis is worse with severe symptoms, associated angio-oedema, autoimmune markers, and poor antihistamine response. Many antihistamine-refractory cases improve with omalizumab.
Sources & References
🏥BMJ Best Practice(1)
💊BNF Drug References(1)
- Promethazine hydrochloride[management.pharmacological]
✅NICE Guidelines(1)
- Urticaria[overview]
📖Textbook References(1)
- David Randall PhD MRCP (Editor), John Booth PhD MRCP (Editor), K - Kumar and Clark's Clinical Medicine (2025, American Elsevier Publishing Co.) - libgen.li.pdf(pp. 1645)[context]