Diatomaceous earth is a non-toxic natural substance. It’s made from crushed fossils of freshwater organisms and marine life. Through a microscope, the particles look like bits of broken glass. Diatomaceous earth is deadly to any insect, yet completely harmless to animals. It can kill fleas, ticks, lice or mites on your dog.It doesn’t poison insects or paralyze them like some pharmaceutical products do. The way it works is purely mechanical. When the razor-sharp particles touch the pests, they pierce the insects’ protective coating. So the bugs quickly dehydrate and die. The particles affect larvae in the same way.