Cure and Prevent
A drastic means (the potions never were affective) was to use alcohol based drink on the scalp, in this case Uzo, although I'd only do it on adults - never a child. The natural prevention treatment is rosemary water - can make a tea with rosemary leaves and boiling water - let cool. Smells nice and seems to keep the lice away (doesn't help if you already have them).