please note: this is not to start an argument on whether DE "works or not." If you wish to debate whether the earth is flat or round i humbly ask you do it elsewhere! rather, this is an atempt to clarify what we do know--scientifically and experientialy--about what DE actually is and what it does and how. as with so many things, I have seen seen so much bizarre info surrounding DE and many weird efficacy claims made about applications of uses that just dont make sense to me and for which it seems no scientific explaination can be provided or that it conflicts with other known facts about the properties of DE. On the other hand, there are those who insist claiming that its completely worthless scam that does nothing useful, which is equally if not more absurd, given the scientific evidence, and ample practical evidence that anyone could see with their own eyes. Anyway, here's some key points I have learned from research and experience: -foodgrade DE (the kind discussed here) is mostly composed of silica (amorphous mainly). i used to think it was mostly calcium--till i actually looked it up... :/ actual mineral ratios can vary a little--not surprising since it is naturally occuring dirt, basically, and comes from different sources. - DE is an effective control for small insects and mites, lice, etc. I does not work like the wave of a wand, but when applied consistently to surfaces frequented or inhabited by such critters, it serves to both dramatically reduce or eliminate populations and deter activity/infestation. i recommend regular applications during severe parasite infestations, and backing off once you see inprovement. (still the stuff is so cheap, and easy and safe to apply this isnt a disadvantage--rather Its the stuff that kills every bug within a 100 yard radius that you should avoid). DE has to actially get on bugs in a relatively generous amount, not just be near them. So using DE in your chicken coop will not destroy neighborhood bee hives, or decimate butterflies. If your BSF bin dies, its probably not because you used DE in the garage--unless you also dumped DE in your larvae bin. Still, like any insecticide, it should be used only as needed, not excessively or when or where it isnt really necessary. and theres nothing natural or admirable about killing things that are just minding their own business. - it kills by damaging the exoskeleton (somehow?) and dehydrating the bugs, not by ingestion, from everything ive read. - It is totally safe for people and non-arthropod animals. as safe as any fine dust anyway... it is foodgrade--you literally can eat it (and we do all the time because its used to protect stored grain) tho why youd want to deliberately is not clear to me. however there is some concern about inhaling it, but apparently the silica in food grade DE is almost entirely amorphous silica, while the kind that causes health problems in oeople seems to be mainly the crystalline silica (like in pool filter DE) and even then the hazards seem to be more occupation related rather than as an occasional exposure? still, its wise to avoid inhaling any fine dust, which just in itself can cause problems. however much of this i gleaned from just one source online, so if you know more, please share... - it has a strong drying effect on deep litter. Despite its non toxic nature, i recommend people use it only ss necessary in coops, not routinely or heavily, because it dries out the litter and makes it very dusty--and breathing any dust regulary is not great for you or the birds (also, inhaling poultry dander regularly and heavily over a long time can cause lung problems, and thus creating a dusty environment where dander particles more readily become airborn creates an increased risk). this drying effect would also interfere with the microbial activities in an proper deep litter. conversely, DE can also be used to dry out litter that accidently gets too wet and keep it from becoming anaerobic, so it works both ways. But silica itself will not "kill all the good microbes"--its the altering if the moisture level that effects this. it can hwever directly kill roaches, isopods, and other critters living in the litter that may provide free feed or other benefits to the deep litter, which can also be a con. in my experience, its eficacy is maximized and its downsides limited by using it mainly on places like roosts, nestboxes, doorways, and around feeders and waterers, where exoparasites tend to congregate/lurk--or in bad cases of lice or mites, on the chickens themselves, particularly around vents, under wings, etc. until some control is achieved. - realize also that it is relatively inert (some microbes can eventually break down silica, i understand) so it stands to reason it shouldnt need to be reapplied where you know its still present, unless it has gotten damp or been scattered or brushed away... (right??) - DE can kill external parasites--but i dont understand how it works as an internal wormer? if it kills arthropoda by damaging the exoskeleton and dehydration, how can it kill an animal with no exoskeleton inside the wet environment of a vertibrates digestive system?? if anyone has information to support such claims, please share... hope this helps!!