Pyrethrins with piperonyl butoxide are a synergistic combination product used topically for the treatment of lice infestations. It is considered the drug of choice for lice (1). Although no reports of its use in pregnancy have been located, topical absorption is poor, so potential toxicity should be less than that of lindane (see also Lindane) (2). For this reason, the use of the combination is probably preferred over lindane in the pregnant patient.