DE is diatomaceous earth or fossil flour. I understand it is ground up fossils. I bought 50 pounds recently, before it turned cold outside. There's a difference in de that we bought mistakenly at Southern States and the 50 pounds we bought. Food grade won't harm any pets or critters or humans unless they inhale the dust. We put it in the chicken coop when we clean it out under the clean bedding. The first time we did that the temps were still quite warm and the flies were so bad we had fly tape hanging in our garage and inside the house from chandeliers. Unbelievable. We put the de in the coop and within days the fly population was down to minimal. Equally unbelievable. We mix some in the chickens food and the dog food occasionally and since we have had a bad case of fleas this year we use it on the dog's and cat's fur, as well as dusted the house. Fleas gone-we spent a fortune on chemical products from the vet that didn't work first. I didn't want to buy de online because shipping costs are horrible but found a distributor within 30 miles. The savings was worth the 30 miles. DE has lots of uses and I will never again be without it.