PROBLEM TO BE SOLVED: To provide an IALD (Indole-3-aldehyde) production promoter that promotes IL-22 production and promotes the production of antibacterial peptides and mucins.SOLUTION: The present invention provides an agent that can safely promote the production of IALD, by comprising Bifidobacterium bacteria, particularly Bifidobacterium longum bacteria as an active ingredient.SELECTED DRAWING: None【課題】IL-22の産生を促進し抗菌ペプチドやムチンを産生する促進するIALD(Indole-3-aldehyde)の産生促進剤の提供。【解決手段】ビフィドバクテリウム属の菌、特にビフィドバクテリウム・ロンガムの菌を有効成分とすることで、安全にIALDの産生を促進し得る剤。【選択図】なし