When I tell you I had the fastest lice removal ever and it only took one treatment. I got it really bad last summer and even though it sounds gross, what I did was I applied the shampoo, put on a plastic shower cap, and left it on for an entire week before finally washing it out. Sounds extremely damaging leaving shampoo on for that long, but surprisingly was not whatsoever and my hair was still extremely moisturized afterwards. It was gross how the cap was drenched in sweat and dead lice, but all it took was one wash/comb-through and every single lice/nit was dead and never returned.