AP BIOLOGY

Detailed explanation-1: -Mast cells release histamine as well as other vasoactive molecules, which cause urticaria (hives). If the antigen activates mast cells in deeper tissue, this can lead to angioedema. If the response is prolonged, atopic dermatitis or eczema may occur.

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: -As such, histamine and other mast cell-derived factors may be indirectly responsible for the vasodilatory effects of CRH, although CRH is also known to act directly on the vasculature. CRH-induced vasodilation in human skin was examined using laser Doppler flowmetry and iontophoresis in adult females.

Detailed explanation-4: -Vasoconstriction is followed by vasodilation and increased vascular permeability, as a direct result of the release of histamine from resident mast cells.