Abstract: Compositions are provided to immobilize and protect oxidase enzymes from proteolytic and hydrolytic attack, utilizing a porous, inert organic, or inorganic, substrate matrix useful in generating hydrogen peroxide in situ for use in oral, topical mucosal and intracavity uses for use in or on the human body and other mammalian, reptile, fish and amphibians. The selected porosity of the support matrix provides the basis for generating hydrogen peroxide on a steady state basis. Both diatomaceous earth and silica gel, either in natural or pre-silanized forms, allow for the excluding of non-preferred enzymes from the support matrix, and for diffusion of the peroxide in the reduction of oral pathogens and their attendant malodorous compounds, or other pathogens in the mucosa, bodily fluids and cavities, in addition to oxidizing color bodies to affect bleaching.