:th It would help if I looked at the OP's location!
We have a "secret weapon" named @Wickedchicken6 from Canada that has given some great info on products in Canada! @jmonahan check out the threads below...
See post# 3...
Poultry Lice nits (eggs)?
Check your girls over very well for any external parasites. If you find any treat the chickens, clean out the coop/bedding/nesting boxes with Permethrin based poultry spray or dust. You can also use Spinosad - I've heard it works well, but is pricey.