Definition
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Urticaria (hives): transient, pruritic, erythematous wheals due to mast cell degranulation and histamine release.
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Duration of individual lesions: <24 hours.
Key Types
| Type | Duration | Common Triggers |
|---|---|---|
| Acute | <6 weeks | Foods, drugs, viral infections |
| Chronic | >6 weeks | Idiopathic, autoimmune, thyroid disease |
| Physical | Triggered by physical stimuli | Cold, heat, pressure, exercise (cholinergic) |
💡 High-Yield Tip: Chronic urticaria is usually idiopathic or autoimmune, not allergic.
Common Triggers
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Drugs: penicillins, NSAIDs, aspirin, opiates
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Foods: nuts, shellfish, eggs
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Infections: viral URTI, hepatitis
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Insect bites/stings
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Idiopathic
Exam Trap: If urticaria occurs immediately after a drug or food, think IgE-mediated hypersensitivity → risk of anaphylaxis.
Clinical Features
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Pruritic wheals: raised, erythematous, blanching, transient (<24 hrs).
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Angioedema: deeper swelling of lips, eyelids, tongue, airway.
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Systemic signs suggest anaphylaxis: hypotension, wheeze, airway compromise.
💡 High-Yield Differentiation:
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Wheals <24h → urticaria
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Red, raised, sharply demarcated → erysipelas
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Poorly demarcated, deeper → cellulitis
Investigations
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Usually clinical diagnosis only.
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Chronic/recurrent: FBC, thyroid antibodies, autoimmune screen.
Management
First-Line
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Non-sedating antihistamines (cetirizine, loratadine, fexofenadine).
Refractory / Chronic
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Higher-dose antihistamines
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Short-course oral corticosteroids for severe flares
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Specialist options: omalizumab, montelukast
Emergency (Angioedema/Anaphylaxis)
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IM adrenaline 0.5 mg (1:1000) in adults
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Oxygen, IV fluids
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Adjunctive antihistamines and steroids
💡 High-Yield Exam Tip:
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Airway compromise + hypotension → treat as anaphylaxis, not just urticaria.
Complications
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Airway obstruction (angioedema)
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Anaphylaxis → life-threatening
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Chronic urticaria → quality of life impact
PLAB-Style Questions
Q1: A 28-year-old man develops widespread, itchy, transient wheals 30 minutes after taking penicillin. No respiratory symptoms. What is the first-line treatment?
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A. IM adrenaline
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B. Oral non-sedating antihistamine
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C. Oral corticosteroid
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D. IV fluids
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E. Observation only
✅ Answer: B. Oral non-sedating antihistamine
(Stable patient, no airway compromise → antihistamine first-line).
Q2: A 35-year-old woman develops urticaria with tongue swelling, stridor, hypotension, and tachycardia after a bee sting. What is the most appropriate immediate management?
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A. Oral antihistamine
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B. Oral corticosteroid
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C. IM adrenaline
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D. Observation
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E. IV antibiotics
✅ Answer: C. IM adrenaline
(Rapid airway compromise + hypotension = anaphylaxis).
Quick High-Yield Pearls
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Lesions <24 hrs → urticaria.
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Angioedema = deep swelling; monitor airway.
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Acute urticaria usually self-limiting; treat symptoms.
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Chronic urticaria often idiopathic; consider autoimmune causes.
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Emergency = airway + cardiovascular compromise → adrenaline IM.
