Since this seems a hot topic in blended families ... here is the other side of the coin!
DD13 has never had head lice ... until now, that is! A few weeks ago, when sitting next to her on the train, I had the shock of my life, seeing that her head was crawling with them (I think we counted about 10-12). Strangely enough, I had actually put curlers in her hair the night before, and then pinned her hair up the next morning (we were going to the horse races and wanted to look all pretty) ... I hadn't noticed.
I obviously informed school immediately (they said they were having an infestation currently), I informed all her friends who she is in close contact with, and obviously I immediately informed BF so he could check his skids.
When I had noticed the lice, I immediately treated her (and myself, since we found one lonely louse on my head) ... and then, for the next four days, wet-combed her hair (and mine) twice a day with conditioner. She didn't have any crawlies when she left for her father's house, but I was still able to spot the odd egg.
I informed BF on how to treat her hair (wet-combing), which he did in accordance with our school nurse's instructions. Three days after she returned from BF's house, she had lice ... still? Again? I don't know, they are definitely less than before ... but they are lice. Oh, and we found another two on my head. We obviously treated again ... and are now back to daily wet-combing (both of us).
On both occasions, I washed all of our bedding on hot, put it in the dryer ... nuking those little buggers! I desinfected, hoovered, quarantined, sprayed with tea tree oil, bleached all of our combs and brushes ... the lot!
Then I called BF again and advised him to check his skids once more to avoid cross-contamination ... and was met with a really shitty attitude! He is obviously the expert on the life of a louse, he is convinced he knows where they are coming from (the stables ... though only one little girl there had them ... we actually think DD gave them to her carrying her piggy-back, and the mother has treated the girl repeatedly). Oh, and he knows why they are still there ... because I'm such a crappy mother.