I was told by a Canine nutritionist that I could use Diatomaceous Earth for my Cat that is constantly getting worms from eating the prey it kills. She said to just add to the Cats food, so if it's safe for a Cat I'm sure it would be OK for a dog. Ask your Vet or do some research first and ask experts as this was just a casual conversation I had. I have not tried it on my cat yet...but, I am going to try.
Diatomaceous Earth and Dogs