After treatment with lice-killing shampoo, you'll have to keep removing nits as you find them. Most of the shampoos only kill live head lice and leave the nits to hatch. Both of the over-the-counter products recommend retreatment after the nits have hatched and before the new lice get old enough to lay more eggs. Retreatment after using prescription lice shampoo may or may not be necessary.
