IMMUNOLOGY

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: -Mast cells and basophils represent the most relevant source of histamine in the immune system. Histamine is stored in cytoplasmic granules along with other amines (e.g., serotonin), proteases, proteoglycans, cytokines/chemokines, and angiogenic factors and rapidly released upon triggering with a variety of stimuli.

Detailed explanation-3: -Mast cells are multifunctional bone marrow-derived tissue-dwelling cells that are the major producer of histamine in the body.

Detailed explanation-4: -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.