lemurchaser you are absolutely correct that ivermectin pour on will kill lice/mites. However, if you use ivermectin prior to using wazine17 and your chickens are possibly infested with worms,you could possibly kill your chickens from the toxicity from the dead worm overload. Ivermectin kills many many types of worms. Wazine17 gets rid of one type of worm,the most common type that chickens have...roundworms. You use the wazine first to lessen the wormload to prevent toxicity,then 2 weeks later use the ivermectin pour on to kill roundworm larva and a host of other worms. BTW, wazine only paralyzes roundworms,ivermectin kills them all,except tapeworms. Egg_newton has an immediate issue to address mites/lice on his chickens and needs immediate treatment. Sevin dust has been used by farmers and gardners for years, as I have in my garden for the past 35 years. I've used it on my dogs throughout the years and now on my chickens for thr past 5 years with no ill effects. Both wazine and ivermectin are poisons designed to paralyze or kill parasites. If worms are excreted as well as throwing away contaminated eggs, where do the dead worms and eggs go to? Yep in the soil, contaminating the soil,possibly the water table. What do you do with an expired bottle of wazine or ivermectin? I know for fact that ivermectin has label warnings about soil and water contamination, said so on the 5 liter jug I had. DE,cayenne pepper,vermx,VetRx etc... are not wormers and will not kill worms.They are good preventatives and that's it. Also as long as sevin dust is being sold,I'll continue to buy it and use it and recommend it in a heartbeat because it works just like ivermectin,which is off label as well.