Despite anecdotal reports of its efficacy, there is little scientific evidence that vinegar kills lice, according to the Minnesota Department of Health. The recommended treatment for head lice is application of an over-the-counter or prescription pediculicide, a medicine that kills lice, states the U.S. Centers for Disease Control and Prevention.
Over-the-counter lice treatments such as A-200 and Pronto contain pyrethrins, which are natural insecticides derived from the chrysanthemum flower, explains the CDC. Brands such as Nix contain permethrin, a synthetic pyrethroid. Because neither of these substances kills lice eggs, they are usually reapplied after nine to 10 days.
Prescription medicines to kill lice include topical 5-percent benzyl alcohol, malathion and ivermectin, notes the CDC. None of these kill lice eggs, but ivermectin appears to prevent them from hatching, so most people only need to apply it once.