dermatologic disorders
Urticaria
Pathophysiology of Urticaria
Urticaria results from the release of histamine, bradykinin, kallikrein, and other vasoactive substances from mast cells and basophils in the superficial dermis, resulting in intradermal edema caused by capillary and venous vasodilation and occasionally caused by leukocyte infiltration. The process can be immune mediated or nonimmune mediated. Immune-mediated mast cell activationincludes Type I reactions, in which allergen-bound IgE antibodies bind to high-affinity cell surface receptors on mast cells and basophils Autoimmune Disorders , in which antibodies to an IgE receptor functionally cross-link IgE receptors and cause mast cell degranulation Nonimmune-mediated mast cell activationincludes Direct nonallergic activation of mast cells by certain medications or substances Drug-induced cyclooxygenase inhibition that activates mast cells by poorly understood mechanisms Activation by physical or emotional stimuli; mechanism is poorly understood but possibly involves the release of neuropeptides that interact with mast cells 