Diatoms are tiny single-celled algae with a really high proportion of silica, and diatomaceous earth is the naturally occurring fossilized remains of them. It kills lice by basically slicing them till they bleed to death. It kills worms in the chook's guts the same way. I've not really used it because garlic works so well for all internal and external parasites, but it's another healthy alternative, though obviously you don't want to breathe too much in, as with most substances. It occurs naturally. It's used for many species and other purposes. So is garlic, which in my opinion can be added to, not taken away from, as basically nothing takes garlic's place in combating viruses, bad bacteria, all parasites, and basically anything unhealthy. Prevention's far better than cure, and garlic's one of the easiest cover-all's.