Immunoglobulin E (IgE) is a member of the antibody family primarily involved in allergic reactions and defense against parasitic infections. It consists of two heavy chains and two light chains, featuring a unique Fc region structurally, allowing it to specifically bind to IgE receptors on the surface of mast cells and basophils. IgE is predominantly localized in mucosal tissues and the skin, participating in immediate hypersensitivity reactions by promoting the release of histamine and other inflammatory mediators from cells. It triggers immune responses by activating various signaling pathways such as the FcεRI signaling pathway. The expression of IgE is gene-specific, regulated by cytokines like IL-4 and IL-13. Specific gene mutations or polymorphisms are closely associated with abnormal IgE levels and susceptibility to allergic diseases.