Do you mean mites or lice ?

2 very different organisms.

Frontline will kill lice and fleas.

Mites esp' red mites (look in crevices , under pearches etc) live in housing not on birds. Come out at night to suck blood. - Look for unthrifty hens , pale combs , anemia , reluctance to go in housing at night.

Only cure I have found is to disinfect hen house.

Only one product will kill mites and mite eggs  -this is a disinfectant called interkokask.

It is approved by Deffra and the british egg council. I can tell you it works !!!!

Use at 3% solution and thoroughly wet all house. Repeat at 7 days - fantastic.

Not a cheap product , they want about £45 for 1 litre conc.

Have been in trouble on other forums for recommending it as it is only available via your veterinary surgeon  but appears to be available online stores  and well known auction sites.

Speak to your vet and ask for a prescription -it works !!

rgds George.