For the first time in .... well .... ever, we are having a terrible time with lice. My daughter has a little friend - her best friend - who comes home from the weekend with her dad and his new family with head lice, like every third time she goes.
My daughter has gotten it from her more than once, now. My daughter has ridiculously thick hair, so getting all the nits is a nightmare.
What I ended up doing is, everytime she spent the night at the little girl's house, she came home and got a lice treatment just as a preventative. I didn't wait to see if I found one, I just washed it out.
Nix brand is the only one that kills lice and the eggs.
If you don't want to use lice shampoo, use olive oil. Just saturate their hair in olive oil, let them sleep in it, then wash out and go over really well for any nits. They will also have super soft shiny hair :)
When they come in or when friends go home, strip them immediately and wash their clothes and treat their hair. If they or someone else has been in their bed, wash the linens in hot water. Put stuffed animals and pillows in the dryer on high heat for an hour. Get the lice spray and treat carseats and apholstery along with whatever anyone sat on and the mattresses.
That's what I would do.