Looks like they're a mix of isomers. Here's one that's 45/55%:
http://www.drugs.com/vet/y-tex-gardstar-garden-poultry-dust.html
The info on isomers is just below the active ingredient information. If you have a different brand, you can probably look it up on the same website, or it might be...
Sometimes it "helps" when an enthusiastic newbie comes on board? I actually like periodically reviewing all my old assumptions/information, so I do a lot of mentoring for interns and what not...bursting with all the information and research they learned in school. We usually end up teaching...
"When topically applied, pyrethroids are absorbed and widely distributed to tissues, but concentrate particularly in fat and skin (Hunt et al., 1979; Braun et al., 1981; Heitzman, 1997, 2000). Residues in skin and fat are very persistent, as are residues in the egg yolk (Hunt et al., 1979; Braun...
If it's just dirt, then keep treating the chickens until the louse life cycle is complete. DE will help, but not if it's moist. I don't know how your ground is right now, but mine is absolutely soggy! You can also use the permethrin dust that QueenMisha suggested in the run, but if you use...
Yuck!
Okay, first thing-- you can't get lice from chickens. Won't remove that creepy-crawly feeling, but it is a relief!
Depending on the species of louse, it could be what is making your birds sick (some suck blood, cause anemia, etc.) or it could be a side effect of sickness because sick...