After seeing OTC products (Vamousse and Licefree) that kill both lice & nits that have an active ingredient of sodium chloride (table salt) since it dehydrates them, I make my own.
Roughly 3/4 table salt and 1/4 liquid dial hand soap (I would assume any liquid, even water would work since the salt is the key ingredient)....just enough liquid to make a spreadable paste out of the salt. I then saturated my daughter's head with it (mine too just to be sure even though a quick self check didn't turn up any lice or nits) and put a shower cap on for four hours.
Then the salt & soap got washed out.
My daughter's school has a "no live lice" policy but not a "no nit" policy so while I wanted to get rid of nits (alive or dead). I slathered our heads with conditioner and combed for a couple hours with a fine-tooth rat tail comb. I'm sure she had lice for at least a couple weeks since I got hundreds of nits out of her hair during that first comb out (none out of mine).
I continued the conditioner / comb out 1 - 2 times a day until I saw no nits come out. It took over a week to get them all out (in that time I never combed out any live lice so that confirmed that in all likelihood the salt mixture had indeed killed the nits as none of them hatched). More than once it was tempting to give her a pixie cut (wouldn't "get rid of them" but would make the comb out process a bit easier in shorter hair than her shoulder-length hair--I have very short hair and my comb out, combing thoroughly in all directions took me under 15 minutes, hers took 1 - 2 hrs-- and she would love the cut for any reason, but I didn't feel confident enough in my hair cutting abilities to do a good cut and I couldn't take her to a salon with nits in her hair, even if they were dead, so I just had to be thankful she didn't have long thick hair to work through).
Since getting rid of our infestation, I've taken preventive measures and added spraying our hair with tea tree oil & water every morning before we leave home / she goes out to play.
So far no new lice.