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What is 'super lice' and how can you treat it?
01:36 - Source: KTXL

Story highlights

Research suggests a large number of head lice in the U.S. have genes that could make them resistant to over-the-counter treatments

Experts still recommend these over-the-counter products, as well as combing, as the first line of defense against head lice

Companies that offer lice removal services, including combing and hand removal, are doing a "booming" business

CNN  — 

Head lice are a lousy part of the school year or summer vacation for an estimated 6 to 12 million children in the United States every year. Infestations can lead to itchy scalp, irritability and poor sleep.

To make matters worse, there are hints we could be losing some of our easiest and cheapest defenses against these insect interlopers. Studies suggest many lice – “super lice,” some call them – may no longer be killed by over-the-counter treatments such as Rid shampoo or Nix rinse.

Newer generation lice-fighting chemicals are an option if the usual treatments fail, but they are often more expensive. A number of parents are taking their children to “nitpickers,” who manually remove the insects from hair using combs and sometimes just their fingers.

Reports of lice resistance started appearing in the mid 1990s in the United States, Europe and Australia. A 2014 study suggested the potential for resistance is high in several areas in the United States and Canada. Among lice samples from 84 people in these countries, 99.6% of the insects had mutations in genes that could allow them to survive the insecticides permethrin and pyrethrin, which are the active ingredients in over-the-counter remedies. In the past, this group’s research has received financial support from pharmaceutical companies that make such prescription medicine.

A 2015 study by the same researchers who did the 2014 study suggests these resistance genes could be widespread in the United States. They studied 109 lice populations from 30 states, each population representing insects from several people. Out of those 109 populations, 104 (95%) contained insects that possessed the genes.

The study was presented in August 2015 at the American Chemical Society meeting. It has not been evaluated by independent experts for publication in a peer-reviewed scientific journal.

In samples from 25 of the 30 states, there were insects that had resistance genes. In some samples, including ones from California, Florida, Maine and Minnesota, every insect in the sample did.

“It’s almost saturated with [these genes], which means that people using permethrin and pyrethrin based products will probably have a very hard time controlling the lice,” said Kyong Sup Yoon, associate professor of biological sciences and environmental sciences at Southern Illinois University, who led the research for the current study and the 2014 study.

Yoon’s research was funded by Sanofi, a pharmaceutical company that owns Sklice lotion, which contains a newer generation lice-fighting chemical.