If you have treated unsuccessfully, you may want to try an alternative product which lice do not have a resistance to. Most experts agree that lice cannot survive for more than about 48 hours off the human head. Nits must feed within two hours of hatching. Pets do not carry human lice. Nits take a maximum of 10 days to hatch.
Personal research suggests in almost all cases nits hatch within a week.
I just got a note from school saying there has been a lice outbreak. Preliminary studies and testimonials indicate that lice cannot stand the scents from the natural essential oils in Lice Off. Lice Off added to shampoo on a daily basis has prevented infestation for tens of thousands of people. Leading pest control experts say that it does little good to try to treat the environment. Reasonable care should be taken to wash bedding and clothes in hot water.