There is another DE product for pools which is not the same, and is not safe for pets, or humans. Apparently Food grade DE is used on farm animals for pests and de-worming. DE has some beneficial trace minerals such as"calcium, magnesium, iron, potassium, sodium, titanium, boron, manganese, copper, and zirconium". I've used DE in my garden for years, and now I use it inside my house for ants, fleas, and other pests; and directly on the cat.
If you are not careful, it can be quite dusty to apply. If you have asthma, it will probably aggravate it, so a mask is recommended. I've found that I don't get any dust cloud if I gently rub(gentle petting) in about a tablespoon at a time into my cat's fur. It helps to do it outside or near an open window, just in case your pet decides to shake. I'm careful about not getting it into my cat's eyes or near his nose.
If you want to get a nice concentrated line of DE on the floor, or puff into small spaces for pests, try using a bottle with a small squeeze type applicator, like a refillable condiment bottle. They sell DE in these bottles, but it is less expensive to purchase the bags and add your own to a bottle.
Diatomaceous Earthin bottles and bags at Amazon.