Shampoos that contain essential oils, such as tea tree oil, peppermint and lavender oil, are somewhat effective at repelling head lice, according to Healthline. However, studies have not shown, conclusively, that these shampoos kill head lice. They should not be used to treat head lice.
These shampoos prevent the transmission of head lice because they make the hair too slippery for the lice to adhere to, according to the "International Journal of Dermatology." Some studies have shown that, while mildly effective, these shampoos do not prevent all transmissions of head lice. Basic preventive measures should still be followed at all times.