A stabilized aqueous composition capable of producing or, in the presence of saliva or other humoral fluid, leading to the production of antimicrobially effective concentrations of hypothiocyanite ions (OSCN-) are herein described. The composition contains an oxidoreductase enzyme and its specific substrate, for the purpose of producing hydrogen peroxide of at least the minimum effective concentration, and in addition, catalase for the destruction of hydrogen peroxide to prevent premature oxidoreductase enzyme decomposition. Optionally, a peroxidase enzyme may be included to act upon the aforementioned hydrogen peroxide, thereby oxidizing thiocyanate ions to produce the antimicrobial concentrations of hypothiocyanite ions (OSCN-).