the same problems can come from 7 dust.
i know this will make some of you cringe - for a small flock owner DE and 7 Dust might be the way to go. i blinded a hen in one eye with 7 dust, and started looking at alternatives. for flocks of any size (if its available to you) ground tobacco stalks mixed with bedding will work great as a preventative. even throwing a pinch of bulk bagged tobacco in the bedding will help.
with as many chickens as we have, i prefer Ivomec pour on- for chickens i dont plan on eating. i dose it with a syringe at 1/8 cc on my small bantams up to 1/4 cc on medium sized chickens, and 1/2 cc on turkeys. it kills the bugs and worms them at the same time.
some people mix a solution of lime and water and paint the inside of their coops with it, i cant tell you if it works; but its cheap and by others statements it is supposed to work well.
i've talked about this somewhere before, and i have not used it on chickens. but spinosad is an organic that should work fine on chickens and kill bugs. i only know of it as a liquid concentrate for around $20 a bottle. its a bacteria that feeds on spent fermenting grains. if i remember correctly on vegetables there was no withdraw periods before you could eat them.