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.
Burkhart CG
Department of Medicine, Medical College of Ohio, Toledo, Ohio, USA.
Burkhart
C N
CN
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