IFN-γ is a Th1 cytokine, reported to suppress allergic reaction by a variety of mechanisms such as regulating allergen presentation to T lymphocytes, enhancing differentiation of naïve T lymphocytes into Th1, and inhibition of Th2 lymphocyte differentiation and suppression of Th2 cytokine release from Th2 activated cells [49]. This evidence concerns the gene IFNG and allergic disease.