head lice

A mom writes in asking for advice about head lice. She says that, unfortunately, she and her children have contracted head lice. She has been running down the list of treatments and common recommendations, but so far, the problem persists. After trying things like Nix, combing, and even putting mayonnaise on her own head under a plastic bag. But she says her son, at least, is still scratching, despite the fact she doesn’t see any lice when she looks. What else should she try?