A few things to correct here. 1) In the US there has been a startling rise in the resistance to the pyrethroid pesticides, which has contributed to the rise of persistent cases of head lice

2)Nits take anywhere from 7-10 days to hatch so any retreating should be done after no less than 10 days 3)nontoxic treatment should always be the choice as there are ways to end lice infestation without exposing children to pesticides.The LouseBuster kills over 99% of nits with nothing more than heated air