well, we judt had a "bout" with lice recently and I also tried the rosmery and tea tree oil, but with limited success. I think that it is probably good as a preventitive but, I have since found something much much better!
neem oil!! it really works!!
there is a company that makes a shampoo & conditioner & oil called thera neem by organix(they carry it in whole foods) it is safe ,gentle smells good and really works. you could just by the oil and then add it to a carrier oil or a few drops in a spray bottle with water for bedding , furniture & clothes.
Neem oil is from India where it is called the "cure all oil" and is both very effective for lice and many skin problems and is so gentle you can use it on a baby. I would (Ido
) use it as a preventitive and since we have started using it we are "lice free". If your dc actually has lice or nits it is very important that in addition to using the oil/shampoo/ conditioner etc; you use the metal comb since that is the most effective tool for getting nits out.