I've read elsewhere that a few drops of tea tree oil in your shampoo will prevent head lice from returning once they're eliminated.
I've been lucky with that. Fourteen years as a teachers assistant and three kids and I never had to deal with it. I did check many little heads for it at school though. If you still see nits (very small white or clear eggs attached firmly to the hair shaft), there's a comb you can buy that has a static charge that will remove the nits. You will most often see nits in the hair directly behind the ears or at the nape of the neck. They must be combed out, the shampoo won't kill the eggs.
Bag all stuffed animals and throw pillows for at least a month in a tightly closed plastic bag.
I don't know if the tea tree oil is for real, but others swear by it. Good luck
