Dr Greengood Topical Lice Killer is guaranteed to kill head lice upon contact. It is 100% non-toxic to humans, pets and the environment. It has been certified safe and effective by an independent testing laboratory. There is no other non-toxic product as effective. Dr Greengood Household Lice Killer is formulated to treat those areas of the home that have come into contact with an individual that has been affected by head lice to prevent additional human infestation.