Hedrin doesn’t use pesticides. It’s made of dimeticone and is very effective from my experience.

“PDMS is effective for treating lice in humans. This is thought to be due not to suffocation (or poisoning), but to its blocking water excretion, which causes insects to die from physiological stress”

https://en.m.wikipedia.org/wiki/Polydimethylsiloxane

You don’t need to shave your head if you get lice! There are many treatment shampoos for lice.