Clinical evidence of lice resistance to over-the-counter products.
BACKGROUND
Over-the-counter insecticidal solutions continue to be the mainstream treatment for most cases of head lice. Recorded insecticidal activity 15 years ago was at 100%, with ovicidal kill at 80%. Recently scattered accounts of possible resistance have surfaced.


OBJECTIVE
This article is to document the general consensus that head lice are becoming resistant to standard over-the-counter therapies.


METHODS
Direct testing of lethality of adult lice with permethrin and pyrethroid was assessed.


RESULTS
Present over-the-counter products proved to be successful in only 9 of 32 head lice tested (28% insecticidal activity).


CONCLUSIONS
Our series of cases further documents that over-the-counter head lice preparations no longer achieve high levels of insecticidal activity, suggesting increased resistance to these insecticides.
Department of Medicine, Medical College of Ohio, Toledo, Ohio, USA.
Burkhart CG
C N
CN
Burkhart
D000818:Animals; D002648:Child; D004338:Drug Combinations; D004352:Drug Resistance, Microbial; D006801:Humans; D007306:Insecticides / Q000494:pharmacology / Q000627:therapeutic use*; D010373:Lice Infestations / Q000188:drug therapy*; D010374:Pediculus / Q000187:drug effects; D026023:Permethrin; D010882:Piperonyl Butoxide / Q000494:pharmacology / Q000627:therapeutic use*; D011722:Pyrethrins / Q000494:pharmacology / Q000627:therapeutic use*; D012536:Scalp Dermatoses / Q000188:drug therapy*; D017211:Treatment Failure
D004338:Drug Combinations; D007306:Insecticides; D011722:Pyrethrins; C027982:RID; D026023:Permethrin; D010882:Piperonyl Butoxide