Tregs secrete regulatory cytokines such as and IL-10 and TGF-β, which reduce pulmonary eosinophil infiltration, allergy-specific Th2 cytokines (IL-4, IL-5, and IL-13), allergy specific IgG1 and IgE production, allergic rhinitis symptoms, and AHR (Figure 1). Here, IL4 is linked to allergic disease.