الفهرس 
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Abstract
chronic urticaria is defined by the presence of urticaria (hives), on most days of the week, for a period of six weeks or longer. About 40 percent of patients with CU have accompanying episodes of angioedema .The prevalence in the general population varies from 0.5 to 3% although it can occur at any age. None of the theories of pathogenesis of CU has been fully established, the best developed hypotheses include the autoimmune theory. The factors that have been identified as possibly being important in the pathogenesis of chronic urticaria include infections, food additives, medications, malignancy, physical factors, and vasculitis. The etiology of chronic urticaria is unknown in 50% to 70% of cases, and this group is defined as chronic idiopathic urticaria.Eosinophils, sometimes called eosinophiles or, less commonly, acidophils, are a variety of white blood cells and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates.The eosinophil-derived neurotoxin (EDN, also known as eosinophil protein-X) is best-known as one of the four major proteins found in the large specific granules of human eosinophilic leukocytes. Although it was named for its discovery and initial characterization as a neurotoxin, it is also expressed constitutively in human liver tissue and its expression can be induced in macrophages by proinflammatory stimuli.