I don't think anyone asked this yet...But are you absolutely sure that the DE is food grade and NOT the pool kind (that is used to clean pools)? The pool kind has silica in it, which is very harmful and/or fatal if eaten by chickens. The DE you have should have something about food grade on it.
We've used DE (food grade) on our chickens pretty often...I've even read that it's good for humans to eat if you have worms or whatever, but we've used it for preventing lice, mites, and other bugs. One time there was an infestation of flies in our coop and we used DE to get rid of them. Of all the times we've used it, we've had no problems that I know of.
Good luck!
We've used DE (food grade) on our chickens pretty often...I've even read that it's good for humans to eat if you have worms or whatever, but we've used it for preventing lice, mites, and other bugs. One time there was an infestation of flies in our coop and we used DE to get rid of them. Of all the times we've used it, we've had no problems that I know of.
Good luck!