Which of the following mediators released by mast cell degranulation is chiefly responsible for the pruritus and wheal formation in acute urticaria?

• A Leukotriene C4
• B Histamine acting on H1 receptors ✓
• C Prostaglandin D2
• D Bradykinin

Explanation

Histamine released from mast cells acting mainly through H1 receptors on dermal endothelial cells causes vasodilatation, increased permeability, sensory nerve stimulation and pruritus, producing the wheal and flare. This is why H1 antihistamines remain first-line therapy for urticaria. Leukotriene B4, prostaglandin D2 and platelet activating factor contribute to some reactions but do not account for the primary wheal-and-flare response. Bradykinin is the key mediator of bradykinin-mediated angioedema, not of urticarial wheals.

Reference: Fitzpatrick's Dermatology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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