PROBLEM TO BE SOLVED: To provide an allergen activity reducing agent and allergen activity reducing method which can effectively inhibit allergen activity and can be used safely at home.SOLUTION: An allergen activity reducing agent comprises essential oil of woody parts and/or leaves of one or more trees selected from the group consisting of Cupressaceae Chamaecyparis, Cupressaceae Cryptomeria and Pinaceae Abies as active ingredients.COPYRIGHT: (C)2015,JPO&INPIT【課題】アレルゲン活性を有効に抑制することができ、かつ、家庭で安全に使用できるアレルゲン活性低減化剤及びアレルゲン活性低減化方法を提供する。【解決手段】ヒノキ科ヒノキ属、ヒノキ科スギ属及びマツ科モミ属よりなる群から選ばれた樹木の1種または2種以上の木質部及び/または葉の精油を有効成分とするアレルゲン活性低減化剤。【選択図】図1