At the salon where my 4 1/2 yr old gets her haircut, they shared a very helpful tip about preventing head lice.  They recommend using Pert Plus shampoo w/conditioner b/c it has a waxy coating that helps deter the lice.  This is NOT a remedy but just a way to help prevent it.  They do not recommend that you over use it though  - simply use it for every other hair washing or just during the high season for lice.   I got the Pert Plus for Kids which is also tear free, tangle free and has the built in conditioner.  My daughter's hair gets so tangled anyway so this can help kill two birds with one stone.  I use it for every other washing or sometimes every two washings.