The invention provides an allergy prevention method or treatment method, diets and oral drugs enabling prevention/treatment of allergic symptoms without trouble such as systemic adverse reaction, immune deficiency and the like caused by transdermal/intravenous administration of TGF-β. The allergy prevention method or treatment method is to orally administer 100 μg/kg or more of transforming growth factor-beta (TGF-β) relative to a weight of an administration target body and thereby selectively suppress Th2 immune response, while with respect to the diets and oral drugs, the content is set to contain an effective amount of transforming growth factor-beta (TGF-β) therein.
