holistic dog foods

What is Diatomaceous Earth and why would it be added to holistic dog food?
I started feeding my dog a holistic dog food and it says it has this ingredient in it.
It says: “Diatomaceous Earth, a natural fossil shell flour known to fight parasite”.
But if my dog doesn’t have parasites why would I want this to be in his pet food?
So I want to know is it safe that it’s in my dog food? It is one of the last ingredients, so I don’t think there is too much but maybe I should change foods?
But, my dog gets Flea preventative every month called: “Revolution” and that’s really strong stuff. So would it be bad that I’m feeding Diatomaceous Earth and putting on Revolution at the same time???
Please help?
It prevents them.
Yes, it is safe. holistic vets recommends it over the flea chemicals the conventional vet likes to sell.
No, you are fine to do both. DE is not a chemical.
Tail Waggers TV – Holistic Cat Food From Dog Food Recipe