Mast cells express the high-affinity IgE receptor, can become sensitized with allergen-specific IgE and, after crosslinking upon allergen encounter, release potent mediators, including histamine, leukotrienes, tryptase and others, and are responsible for the multitude of local and systemic reactions observed in IgE-associated hypersensitivity reactions [69]. This evidence concerns the gene IGHE and hypersensitivity reaction disease.