It has been suggested that peripheral T-cell tolerance to environmental antigens is crucial for avoidance of allergy, and aberrant activation of Th2 cells in allergy is secondary to impaired mechanisms of peripheral T-cell tolerance that is normally mediated by antigen-specific T-cell anergy, Tregs and suppressive cytokines, IL-10 and TGF-β. This evidence concerns the gene IL10 and Allergy.