diatomous earth

I've never used it on animals, but on plants you apply it whenever it seems to have blown off or after every rain which simply washes it off. I'd expect the hens would need the same application, but perhaps monthly if they're not getting wet at all.  And be sure to keep it out of their eyes when applying.

Hi westie,
I would use an old jamjar put some holes in top to fashion a "sprinkler" or use an old talcum powder container. Then ensure you sprinkle the powder and run right down to the base of the feathers - ensuring vulnerable areas like under wings and vent are treated. (these are the areas lice and fleas love on our chickens!)I think one application should be enough - I would check a week later but others may do this differently. The other thing is I generally do this in the morning - to prevent them inhaling the powder in the coop. As well as sprinkling in their dustbath this should sort them out. The next thing is to ensure the coop is treated at the same time although lice and fleas live on the bird you want to make sure that all are destroyed at the same time. This would also be a good preventative against the dreaded red mite which lives in the henhouse. Hope this helps Aunt Sally I expect will be along with the bits Ive missed!