Human head louse (Pediculus humanus capitis) scrambling over hair. Science Photo Library's Sept. 12, 2016 clip of the week: Video courtesy of FRANCIS CHEE/SCIENCE PHOTO LIBRARY
A review of the efficacy of available over-the-counter (OTC) head lice treatments in the U.S. has found that their efficacy has declined sharply since being introduced in the ’80s, to the point where they are more likely to fail than not.
Investigators searched three major biomedical databases for records from 1985, when the currently common OTC products were first available, to 2014, focusing on U.S. reports.
Data from the U.S. Food and Drug Administration website and labels of approved products were also reviewed.
The authors found a marked decline in the effectiveness of permethrin and synergized pyrethrins which they attributed to resistance arising from widespread and indiscriminate use of these products, as well as the emergence of knockdown resistance mutations.
Other recommendations from the review included: use of lindane should be limited due to its potential toxicity and the availability of safer, more effective alternatives; safe, effective prescription products that are available include malathion, benzyl alcohol, spinosad, and topical ivermectin; and home remedies such as petroleum jelly, mayonnaise, and essential oils have not been demonstrated as safe or effective and may cause adverse reactions.
“Our findings indicate that over-the-counter treatments for head louse infestations are no longer likely to be effective,” Terri Meinking, PhD, president of Global Health Association of Miami, Inc. in Miami, Fla., and co-author of the review, said in a release.
“The lesson we should learn is that those products that do remain effective, which are available by prescription, should be used judiciously so that they do not suffer the fate that has befallen the pyrethroids,” added lead author Dr. Ellen Koch, a pediatric dermatologist at the Children’s Hospital of Pittsburgh in Pittsburgh.