Urticaria – High-Yield Clinical Overview

Definition

• Urticaria (hives): transient, pruritic, erythematous wheals due to mast cell degranulation and histamine release.

• Duration of individual lesions: <24 hours.

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Key Types

💡 High-Yield Tip: Chronic urticaria is usually idiopathic or autoimmune, not allergic.

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Common Triggers

• Drugs: penicillins, NSAIDs, aspirin, opiates

• Foods: nuts, shellfish, eggs

• Infections: viral URTI, hepatitis

• Insect bites/stings

• Idiopathic

Exam Trap: If urticaria occurs immediately after a drug or food, think IgE-mediated hypersensitivity → risk of anaphylaxis.

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Clinical Features

• Pruritic wheals: raised, erythematous, blanching, transient (<24 hrs).

• Angioedema: deeper swelling of lips, eyelids, tongue, airway.

• Systemic signs suggest anaphylaxis: hypotension, wheeze, airway compromise.

💡 High-Yield Differentiation:

• Wheals <24h → urticaria

• Red, raised, sharply demarcated → erysipelas

• Poorly demarcated, deeper → cellulitis

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Investigations

• Usually clinical diagnosis only.

• Chronic/recurrent: FBC, thyroid antibodies, autoimmune screen.

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Management

First-Line

• Non-sedating antihistamines (cetirizine, loratadine, fexofenadine).

Refractory / Chronic

• Higher-dose antihistamines

• Short-course oral corticosteroids for severe flares

• Specialist options: omalizumab, montelukast

Emergency (Angioedema/Anaphylaxis)

• IM adrenaline 0.5 mg (1:1000) in adults

• Oxygen, IV fluids

• Adjunctive antihistamines and steroids

💡 High-Yield Exam Tip:

• Airway compromise + hypotension → treat as anaphylaxis, not just urticaria.

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Complications

• Airway obstruction (angioedema)

• Anaphylaxis → life-threatening

• Chronic urticaria → quality of life impact

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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?

• A. IM adrenaline

• B. Oral non-sedating antihistamine

• C. Oral corticosteroid

• D. IV fluids

• E. Observation only

✅ Answer: B. Oral non-sedating antihistamine
(Stable patient, no airway compromise → antihistamine first-line).

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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?

• A. Oral antihistamine

• B. Oral corticosteroid

• C. IM adrenaline

• D. Observation

• E. IV antibiotics

✅ Answer: C. IM adrenaline
(Rapid airway compromise + hypotension = anaphylaxis).

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Quick High-Yield Pearls

• Lesions <24 hrs → urticaria.

• Angioedema = deep swelling; monitor airway.

• Acute urticaria usually self-limiting; treat symptoms.

• Chronic urticaria often idiopathic; consider autoimmune causes.

• Emergency = airway + cardiovascular compromise → adrenaline IM.