Dow Building Solutions added a bittering agent (Denatonium Benzoate) to its Great Stuff insulating foam sealant in an effort to block out insects and other critters bent on regaining access to the home by chewing through the foam. Pestblock contains no pesticides and forms a long-lasting barrier that is both airtight and water resistant. It can seal and insulate gaps up to one inch and can be used both inside and out. 800.232.2436.