How Effective Is Diatomaceous Earth for Fleas?

By Karen S. Johnson

Diatomaceous earth, commonly referred to as DE, is a chemical-free flea treatment. If you and your pet experience a flea infestation, discuss a flea-treatment plan with your veterinarian before using DE, as your pet may need a stronger medical treatment. Purchase only food-grade diatomaceous earth for use on and around your pets.

Introducing Diatomaceous Earth

Fossilized skeletons of organisms found in oceans, rivers, lakes and streams make up silica deposits that are mined and finely crushed to make diatomaceous earth. DE is commonly available at retail in dust form, but you may also find it as a pressurized liquid or a powder designed to mix with water. The United States Department of Agriculture's National Organic Program allows food-producing participants to use natural DE as a pesticide, and the Food and Drug Administration classifies DE as Generally Recognized as Safe as of 2015. Some formulations have added chemicals for use in swimming pool filters and other industrial applications; do not use them around animals.

How DE Works

The skeletal organisms that make up diatomaceous earth have sharp edges that pierce insects and other small pests just enough to cause dehydration and kill them. However, these sharp particles are too microscopic to have the same effect on animals and humans. According to the Texas A&M AgriLife Extension website, dry DE works best -- a liquid or wettable formulation may not get you the best flea treatment results. Stored DE will never lose its effectiveness as long as you keep it dry. Pests won’t build up a resistance to diatomaceous earth like they do to some chemical treatments.

Your Pet and External Application

Diatomaceous earth is most effective on existing fleas when you apply it directly to your dog or cat. Rub it lightly, as often as necessary, over your pet’s coat. Treat his bedding, kennel and other areas where he lives to kill existing fleas and as a preventative measure. DE works best when it’s undisturbed, so apply DE to living areas frequently, including household carpet. You can use DE outdoors, but you will have to reapply it if the ground gets wet.

Your Pet and Internal Dosing

Mix food-grade diatomaceous earth in your pet’s food to control and prevent internal parasites -- he’ll remove it naturally and quickly from his body before it absorbs into the tissues. Be sure you have your vet's blessing and follow his dosage instructions. Dogs Naturally Magazine reports appropriate dose ranges around 1 tablespoon for dogs 55 pounds and larger and 1 teaspoon for small dogs. Dr. Janet Roark, a veterinarian in Austin, Texas, concurs. Roark advises giving 1 teaspoon to adult cats and a half-teaspoon to kittens. She says dogs and cats over 10 pounds can safely receive 1 1/2 to 2 teaspoons. Seek your vet's counsel for dosage amounts tailored for your pet. You can feed DE to your pet once a day; if you suspect your dog needs it more frequently, consult your veterinarian.


Cover your nose and mouth when using DE, particularly if you have dust sensitivities, as it can irritate nasal passages and cause coughing and shortness of breath if you inhale large amounts. The silica can irritate your eyes and skin. Try to cover your pet’s nose and mouth, as well.