During an allergic reaction, which mechanism explains why exposure to an allergen causes rapid vasodilation and increased vascular permeability in the affected tissue?

💡 Explanation

Mast cell degranulation releases histamine, causing vasodilation and increased permeability, because histamine binds to receptors on endothelial cells, triggering intracellular signaling cascades. Therefore, mast cell degranulation is responsible, rather than direct complement attack or T-cell mediated apoptosis, which are less immediate.

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