To effectively and safely remove allergen in the environment of living esp. allergen caused by mites relating to indoor dust by including a specific hydroxybenzoic acid-based compound as an active principle.

The method of this invention is to include a hydroxybenzoic acid-based compound of the formula (R1 to R3 are each H or OH), e.g. 2,5- dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 2,4,6-trihydroxybenzoic acid, or the like, usually in a quantity of 0.1-50 wt.%. Appropriate carrier and, if needed, such adjuvant for preparations as a dispersant, a wetting agent, a thickener, an antioxidant, an ultraviolet absorbent, or the like are usually added to the compound of the formula to prepare various preparations such as an oil-based product, an emulsion agent, a suspension agent, an aerosol agent, a smoking agent, a fumigant, or the like which are applied to the area where allergen exists.