Think you, I read and re-read the Nutrena web sight a total of 5 times
I would be very interested in the experience of other poultry keepers with the effectiveness of Feather Fixer With Mite-Fighter Technology since the most common and destructive poultry mite, the common chicken mite swarms after dark from the cracks and crannies of the coop and roost poles in order to suck the blood from your fowl, totally bypassing the vent in most instances. Besides, the other mites that live on your chickens more or less constantly can always use the chickens eyes as their water source if they don't like the hard water around your chicken's vent.
This web sight is a good resource to begin to understand the various species of mites.
http://ipm.ncsu.edu/AG369/notes/poultry_mites.html
What the Nutrena web sight did not tell me speaks volumes. No mention was made about chicken lice and Nutrena was very, very, very careful that they did not make the claim that their product would in any way rid your chickens or mine of mites, lice, fowl ticks, stick tight fleas or any other external chicken parasite.
As I mentioned earlier the common chicken mite is not ever present on your chickens during daylight hours so if you look for them when the Sun is up you likely won't find a single common chicken mite. However when the Sun goes down there may be thousands on every bird, but even then they are small, the color of a chicken's skin and therefor hard to see until they are engorged with blood and then turn a bright red or crimson. This mite can live for months without a chicken or other bird to feed on, but once they find a food source look out.