PATHOLOGY

Detailed explanation-1: -Histamine is a major preformed mediator released by mast cells and it strongly increases vascular permeability. This increase in vascular permeability is responsible for several features of acute allergic reactions including edema, urticaria, and anaphylactic shock in serious cases.

Detailed explanation-2: -When mast cells detect a substance that triggers an allergic reaction (an allergen), they release histamine and other chemicals into the bloodstream. Histamine makes the blood vessels expand and the surrounding skin itchy and swollen. It can also create a build-up of mucus in the airways, which become narrower.

Detailed explanation-3: -Histamine is a major factor released during mast cell degranulation. Histamine is a vasodilator and has the capacity to contribute locally to sc blood flow control under normal and pathologic conditions (23).

Detailed explanation-4: -The results showed that histamine induced HMGB1 translocation and release from the endothelial cells in a concentration-and time-dependent manner. These effects of histamine were concentration-dependently inhibited by d-chlorpheniramine, a specific H1 receptor antagonist, but not by H2 or H3/4 receptor antagonists.