The Diatomaceous Earth in my small town's hardware store is sold as 'insect powder' with no mention of whether it is food grade or not. However, it does say on the package that it is useful for killing fleas and that it should be sprinkled around the pet's sleeping area (in the case of my cat Amy, that would be the whole house). The package also cautions against...
...getting it into eyes (human and pet). But there's nothing on the package about treating a dog or cat directly. The wikipedia article on diatomaceous earth says:
In order to be effective as an insecticide, diatomaceous earth must be uncalcinated (i.e., it must not be heat-treated prior to application)... and have a mean particle size below about 12 microns (i.e., food-grade— see below).and...
Freshwater-derived food grade diatomaceous earth is the type used in US agriculture for grain storage, as feed supplement, and as an insecticide. It is produced uncalcinated, has a very fine particle size, and is very low in crystal silica (<2%).So it would seem that being an insecticide means it is therefore food grade. And therefore the product should be OK. But I still don't know how to apply it to the cat.
I have read all sorts of horror stories about chemical flea treatments so the Zodiac flea collar with N-methyl carbomate that I bought a couple of years ago is still in its hermetically sealed plastic wrapper.
The budget is low, so options are limited. Otherwise, I'd buy fresh garlic regularly and put it on Amy's food.
Your opinions and suggestions, please, on an itchy topic.