A patient with a history of anaphylaxis to peanuts carries an epinephrine auto-injector. He asks why antihistamines (H1 blockers) are recommended as adjunctive therapy after epinephrine. The rationale is that H1 antihistamines specifically block which component of the anaphylactic response that epinephrine does not fully reverse?
- A Bronchospasm
- B Hypotension and cardiovascular collapse
- C Cutaneous flushing, urticaria, and pruritus ✓
- D Laryngeal oedema
Correct answer: C. Cutaneous flushing, urticaria, and pruritus
Explanation
H1 antihistamines block histamine-mediated cutaneous symptoms (flushing, urticaria, pruritus) that may persist even after epinephrine reverses bronchospasm and hypotension. Epinephrine is the first-line life-threatening treatment for bronchospasm, laryngeal oedema, and cardiovascular collapse via alpha-1, beta-1, and beta-2 effects. Antihistamines are adjunctive for cutaneous manifestations and do not replace epinephrine for airway or circulatory compromise.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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