As the parent of a five year old, this isn't news to me! From all I read when she was dealing with lice, the over the counter pesticide shampoos in the US hardl

As the parent of a five year old, this isn't news to me! From all I read when she was dealing with lice, the over the counter pesticide shampoos in the US hardly work for anyone anymore (we tried anyway, at the firm insistence of our daycare), and the prescription options aren't that much better (we didn't bother, despite the insistence of our daycare). The good news is that only adult lice actually spread between heads (the eggs won't even hatch away from body temperature: that's why they're attached right next to the scalp). And if you comb carefully for a day or two you'll get rid of essentially all of them. It may take longer to catch all of the immature ones (especially since they'll keep on hatching for a while), so you've got to be vigilant. But a good comb and some effective distraction for the kid while you use it will do the job, and there's no reason to isolate them after those first couple of days. (Sadly, daycare didn't agree.)