Don't think I'd put malathion on my head or anyone elses.
I did get head lice once while out of town staying in a motel doing time domain electromagnetic surveys. Bought a bottle of rubbing alcohol, poured it in my hair, and worked it in. Took a shower to rinse it out. Killed them all instantly and I didn't bring it home.
P.S. this is an anecdotal story and not backed by medical "science" or any comprehensive study. It is therefore, on the EvC forum, regarded as probably a delusion on my part and in fact never really happened.