An allergy develops in two steps: the first sensitization phase occurs when the patient is first exposed to the allergen and his/her immune system acts by developing memory cells that produce specific IgE against the allergen, and the effector phase occurs when the patient is exposed again to the allergen and the specific IgE acts by recognizing it and activating the inflammatory response by the secretion of different substances through mastocytes and monocytes. This evidence concerns the gene IGHE and allergic disease.