I have 6 Silkies, 1 Ameraucana, and 1 Blue Laced Red Wyandotte (all under a year old). They've been shaking their heads and I checked and they have mites crawling on them, mostly in the neck area and on the tops of their heads. I put on some Ivermectin 5 days ago (1/4 cc for Silkies, and 1/2 cc for Ameraucana and Wyandotte), but they have still been shaking their heads. I've also used DE on their bodies and (with a makeup brush) dabbed it on the tops of their heads and their neck areas (I had mites running everywhere, which gave me the heeby-jeebies). I also cleaned and sprayed the coop with Permethrin (diluted to the 1%) and added in fresh pine bedding. After all of that, they still were shaking their heads. So I went and purchased ProZap Garden & Poultry Dust at our feed store and, so far, have put that into their coop & nesting boxes (under the bedding),and also sprinkled some in their sandy run area where they like to dust bathe. Unfortunately, it's been pretty windy here, so I haven't been able to actually dust the chickens with the Poultry Dust yet (and I don't have a helper available). I just don't understand why the Ivermectin didn't take care of all of the mites? Does it normally take this long to work? Maybe I didn't use enough? Can I reapply more; and if so, when? Or any ideas of what else I should do?