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For nits, my sister used to swear by permanent hair dye. Not sure whether you'd want to use it on your daughter.
My sister was infested a few times, and then started dyeing her hair black. That sorted the little sh!ts out - the dye killed them all.

Not sure whether it was something in the dye, or the fact that you stick it on, leave it for half an hour and then rinse - maybe they were suffocated?

I suspect its the harsh chemicals in the dye that kills them. I'd stick to the kids shampoo for nits, wouldn't want to dye my kids hair plus it's probably too harsh on their skins for kids.