Keep dogs and cats happy and healthy. Protect pets from fleas. Diatomaceous earth is an environmentally friendly alternative to toxic commercial flea and tick treatments. Diatomaceous earth is a fine powder composed of the crushed fossilized exoskeletons of microscopic diatoms. This is a remarkable substance that is a desiccant--it actually dries out the waxy outer layer of fleas, causing them death by dehydration. In tests performed by the USDA, as well as a number of consumer trials, diatomaceous earth has proven to be an effective non-chemical insect control.