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Histamine Effects — MFDS Part 1 MCQ

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EasyPhysiologyHistamine EffectsMFDS Part 1

During an immediate allergic reaction, which combination of effects is characteristically produced by histamine released from mast cells?

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Correct answer: B — Vasodilation, increased vascular permeability, and bronchial smooth-muscle contraction

Histamine released during an immediate hypersensitivity reaction causes vasodilation and increases vascular permeability, producing erythema, tissue oedema and wheal formation. At H1 receptors on bronchial smooth muscle, it also promotes contraction and therefore bronchoconstriction. Thus, A gives the characteristic combination. Option C describes the opposite vascular and airway effects. Option A includes vasodilation but incorrectly combines it with reduced permeability and bronchodilation. Option D includes increased permeability but incorrectly states vasoconstriction and bronchial relaxation. Option E includes bronchial contraction but reverses both characteristic vascular effects. Histamine is important in anaphylaxis, although it is only one of several mediators released from mast cells.

Reference: National Institute of Diabetes and Digestive and Kidney Diseases. Antihistamines. LiverTox, 2017. https://pubmed.ncbi.nlm.nih.gov/31643232/