2 home remedies that have always worked in my family (we call head lice "ukus" in Hawaii):

Listerine -- it kills the adults. Follow it up with mayonnaise/petroleum jelly. It'll treat the nits and also kill whatever remaining adults there are. Massage it into the head, and those things come off because it's too slippery for them to hang on. It'll work better with those special combs, though.

It's less toxic and smells better than the prescription stuff.