Triple Response of Lewis — FRCA Primary MCQ
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Correct answer: B — Red line, surrounding flare, then local wheal
The best answer is “Red line, surrounding flare, then local wheal”. Lewis’ triple response consists of a local red line from capillary dilatation, a surrounding flare mediated largely by an axon reflex and arteriolar dilatation, and a wheal from increased microvascular permeability. It is an acute local neurovascular response, not a sequence of bruising, venous obstruction or delayed hypersensitivity.
Reference: Royal College of Anaesthetists, Primary FRCA Syllabus 2021: https://www.rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf