Abstract: Anti-microbial compositions are described which contain iodide and thiocyanate anions, an oxidoreductase enzyme, namely glucose oxidase, and its corresponding oxidisable substrate, D-glucose. Such compositions may advantageously further comprise a peroxidase such as lactoperoxidase. The compositions have excellent anti-microbial properties effective against bacteria yeasts and moulds. The compositions may be provided in concentrated substantially non-reacting forms such as dry powders and non-aqueous solutions which may be diluted to provide compositions with broad spectrum anti-microbial activity. Compositions may be used as preservatives or as active agents providing potent anti-microbial activity of use in oral hygiene, deodorant and anti-dandruff products.