An allergic reaction, as a complex response of the immune system to re-contact with an allergen after sensitization, is associated with the binding of the foreign molecule with specific IgE on the surfaces of mast cells, followed by the release of various bioactive substances and inflammatory mediators, including histamines, leukotrienes, prostaglandins, cytokines, and serine proteases, which are all involved in the manifestation of allergy symptoms such as vasodilation, increased vascular permeability, enhanced mucus production, and the contraction of bronchial smooth muscle. This evidence concerns the gene IGHE and allergic disease.