Abstract: This invention relates to an allergen-reducing composition comprising a hydroxyproline derivative, a polymer thereof, or a salt of such a derivative or polymer, which is capable of reducing the allergenicity of mites, pollens, or other allergens and is capable of imparting functions of reducing allergenicity to fibers or textiles such as a carpet, a tatami mat, a bed cloth, a curtain, clothing, a stuffed animal, a mask, a filter material, or a dust bag for an electric vacuum cleaner without discoloration; and a method for reducing allergens using such composition.