Pediculicide Resistance in Head Lice: A Survey

Abstract

The head louse is an obligate human parasite. Evidence points to the growing resistance of head lice to nonprescription pesticides (eg, synergized pyrethrins, permethrin). To gather data, recent pharmacy graduates were surveyed about treatment failures and resistant lice. The response rate was 28.4%, with 173 of 609 surveys returned. One hundred and thirty-one pharmacists provided information that they had gathered during counseling sessions or other contacts with patients. Patients who remained infested after using either synergized pyrethrins or permethrin were encountered by 81.7% and 78.6% of pharmacists, respectively; these treatment failures occurred once or twice weekly in 58.1% of pharmacists' practices. Patients treating themselves more frequently or in higher doses with pesticides in an attempt to rid themselves of lice were reported by 62.6% of pharmacists. Patients reported the use of gasoline, kerosene, or other dangerous treatments once weekly or more in the experience of 42% of pharmacists. Resistant head lice had been a problem in their areas for 1 or 2 years for 42.8% of pharmacists. A smaller percentage (5.3%) of pharmacists had received official confirmation that resistant head lice were present in their areas. Pharmacists recommended nontoxic options (eg, combing and vacuuming) 19.8% of the time with positive results. Resistance seems to be a widespread, growing phenomenon and is not entirely related to patients' inability to use pesticides correctly. Pharmacists should consider recommending nontoxic alternatives that do not pose a threat to the patient or environment and do not contribute to resistance.