Internal: Diatomaceous Earth is also an effective deworming supplement for pets. It helps to eradicate roundworms, whipworms, pinworms, and hookworms in dogs and cats.
External: Fleas and other insects have exoskeletons, rigid outer bodies, or shells. When these insects touch diatomaceous earth, the tiny abrasive particles damage their exoskeletons and cling to their bodies, absorbing the moisture until they dry up and perish. The particles may also kill some flea larvae, but it is not effective against flea eggs or pupae. Adult fleas may die as quickly as four hours after contact with diatomaceous earth.