Permethrin is a pediculicide available in over-the-counter (OTC) medicines that kill head lice and their eggs (nits) and prevent re-infestation for up to 14 days. The active ingredient permethrin is for head lice only and is not intended to treat pubic lice (crabs). Permethrin can be found in single-ingredient head lice treatments.
Permethrin is approved by the U.S. Food and Drug Administration (FDA) and is safe and effective when used according to the Drug Facts label directions. Prior to using a head lice creme rinse treatment containing permethrin, wash your hair thoroughly with a shampoo that does not contain conditioner. Using a shampoo with a conditioner or using a conditioner alone may decrease the effectiveness of permethrin.