Advantage contains an active ingredient, imidacloprid, that works fast and is able to kill fleas on contact, as it is not absorbed into the bloodstream. The active ingredient remains in the lipid (oily/fatty) layer of your cat’s skin and fur. It also kills flea larvae in the home. As your cat naturally sheds their dead skin and fur, imidacloprid is also shed into the environment. Larvae are killed within 20 minutes of contact with this imidacloprid. This breaks the flea lifecycle.