Pyrethrum extract and piperonyl butoxide are pediculicides available in over-the-counter (OTC) medicines that kill head lice, body lice, pubic lice (crabs), and their eggs (nits). The two ingredients come together in medicines that kill lice and nits.
The combination of pyrethrum extract and piperonyl butoxide 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. It is very important to apply lice treatments containing pyrethrum extract and piperonyl butoxide to dry hair. Wetting the hair prior to use can dilute the treatment.