When lice lay their eggs they stick them to the hair with a sort of glue. This glue is so strong that the empty and dead nits remain permanently attached to the hair. With the naked eye there is no way of telling whether the nit is dead or alive. There is no need to remove empty nits or to cut the hair off when treating for head lice. Elimax® Post-treatment Shampoo is specially developed to make those stubborn nits easier to comb out. For best results it should be used after every head lice treatment. Check the hair again 7 days after treatment. Any nits you may have missed will have become juveniles, and by that point it will be easier to spot them.