got this from a professional. drench hair in olive oil & let sit for 45 mins. Rinse first with dish washing liquid (to remove oil),then wash with regular shampoo & then conditioner. comb hair thoroughly. Repeat this process exactly a week later & all should be fine.
now the trick is that afterwards only use COCONUT shampoo. keeps the nits/lice away. they dont like the smell. i had a major problem 4 years ago & B”H since then all ok.