Head lice are getting tougher to treat
Pests are growing increasingly resistant to over-the-counter treatments, experts say
Recently, a paper presented at the American Chemical Society’s annual meeting in Boston noted that lice resistant to over-the-counter delousing agents called pyrethroids have been found in 25 states, including California.
Experts note that lice have clearly evolved resistance to common chemicals often shampooed into scalps the moment the first nit appears. But that resistance has been building for some time.
“There is no question that there is some resistance in lice, and we’ve been seeing it increasingly over the last decade in the United States,” said Dr. Lawrence Eichenfield, chief of dermatology at Rady Children’s Hospital San Diego.
Just how quickly the resistance has been building is an open question.
The U.S. Centers for Disease Control and Prevention does not require health providers, schools or public health departments to report lice infestations because the insects do not spread diseases. They are simply an itchy, persistent nuisance.
The agency does estimate that 6 million to 12 million infestations occur each year among 3- to 11-year-olds in the United States.
Because statistics are not systematically collected, there is no definitive statement on what percentage of lice have developed immunity to over-the-counter treatments. Also, the parasitic pests circulating in one region of the country could be more or less resistant than those in other regions, Eichenfield said.
Putting aside the issue of data collection, it is not difficult to find plenty of anecdotal stories about local residents infected with hardy lice.
Recently, a national chain company called Lice Clinics of America began using a device that floods the scalp with warm air, drying out and killing lice. Combing is still necessary, although less so than without the dehydration process.
Patricia Willemsen, chief executive for a Lice Clinics of America location in Southern California said she tends to work on children and adults who have already tried insecticide shampoos.
“We definitely have seen an increase during the peak season in the summer,” she said.