The invention relates to compounds from the groups of (A) electrophiles, (B) nucleophiles, (C) alkylating agents, (D) antioxidants and (E) oxidizing agents as odor preventatives for reducing so-called ghost odor which is induced by 2-methyl-4-isothiazolin-3-one and/or octyl-4-isothiazolin-3-one. The invention further relates to biocide compositions which comprise 2-methyl-4-isothiazolin-3-one and/or octyl-4-isothiazolin-3-one and also one or more odor preventatives, and to the use of odor preventatives for preventing ghost odor.
