This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basic Concepts and Vascular changes of Acute Inflammation, Subject name: Pathology
[{'content': 'Lewis triple response is caused due to: \nSelect and explain. \nA. Histamine, B. Axon reflex, C. Injury to endothelium, D. Increased permeability', 'role': 'user'}, {'content': "Answer: A \nExplanation: Lewis triple response is caused due to Histamine When histamine is injected intradermally it causes the triple response consisting of: Red spot: Due to capillary dilatation. Wheal: Due to exudation of fluid from capillaries and venules. Flare: Redness in the surrounding area due to aeriolar dilation mediated by axon reflex. A, 'Triple response' elicited by firm stroking of skin of forearm with a pencil. B, Diagrammatic view of microscopic features of triple response of the skin", 'role': 'assistant'}]