Lactoperoxidase is a type of enzyme secreted from mammary, salivary, and other mucosal glands in humans. For use in cosmetics and personal care products, lactoperoxidase is obtained from milk. Lactoperoxidase is a natural antibacterial agent and is therefore used as a preservative in cosmetic products. Research also indicates that lactoperoxidase has antibacterial properties that can eliminate acne-causing bacteria.

Lactoperoxidase is typically used in combination with glucose oxidase for full preservative effect in a cosmetic formulation. This preservative system involves first adding the substrate solution containing glucose, iodide ions, and thiocyanate to the cosmetic formulation. When added to the formulation, the glucose oxidase enzyme oxidizes glucose into gluconic acid, which converts oxygen into hydrogen peroxide in the process. This results in removal of the usable oxygen necessary for microbial activity. Then, the lactoperoxidase enzyme reacts with hydrogen peroxide to catalyze the oxidation of the iodide and thiocyanate anions. Ultimately, this creates hypoiodite and hypothiocyanite, which both have antimicrobial activit