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For Head Lice, Fourth-Grade Girls Are A Favorite Host

Aaron Hoover

Clay Scherer, (352) 392-2484
Phil Koehler, (352) 392-2484

GAINESVILLE, Fla. — Head lice, the parasites that afflict millions of school children each year, have a sweet spot for 9- and 10-year-old girls, a University of Florida study has found.

The study by UF entomologists concluded that third-, fourth- and fifth-graders were more likely than other elementary school-aged children to have head lice — with fourth-grade girls most likely of all to host to the pesky critters. The entomologists are scratching their heads as to the cause, but they speculate it may have to do with fourth-grade girls’ affinity for hugging each other, combing each other’s hair and otherwise sharing physical contact.

“Neither physiology nor hair length seem to play a role, so that’s the speculation,” said Phil Koehler, an entomology professor in UF’s Institute of Food and Agricultural Sciences. Koehler oversaw the study.

Between 6 million and 12 million children are afflicted with head lice nationally each year, according to previous studies. Although the pests do not carry any diseases, they cause discomfort and may result in missed school as children are kept at home until the problem is controlled. Outbreaks are common in the fall, when children return to school, but head lice are a problem year-around, health officials say.

Many children respond to treatment quickly and without much problem. But some children are chronically infested, or are unable to eliminate the pests despite repeated treatment. For the study, Clay Scherer, a UF entomology doctoral student, worked with school nurses in Alachua County’s 24 elementary schools to identify 52 such chronically infested students — who are thought to play leading roles in school or community outbreaks because they carry the parasites for extended periods, Scherer said.

The majority, Scherer found, were third-, fourth-, and fifth-graders, with fourth-grade girls comprising the largest group, he said.

Koehler said school officials should take that information into account when screening children and trying to combat outbreaks.

“Right now, when outbreaks occur, schools often screen all their students,” he said. “If they can focus in on the children most likely to have lice, they can save time and are more likely to have an impact on the problem quickly.”

Scherer’s study also bolstered earlier studies — and many parents’ experiences — suggesting that popular over-the-counter anti-lice shampoos are only partially effective.

While previous studies of the shampoos relied on tests of the products in laboratory conditions, Scherer removed lice from the 52 infested children immediately after they had been shampooed and monitored their fate.

His findings: Only about half the lice exposed to the products wound up dying.

Teri Hardwick-Allen, a school nurse at Norton Elementary School, said that jibes with her experience trying to rid children of lice.

“I don’t find that anything over the counter works,” she said.

The situation is only likely to worsen as lice continue to build up immunity to the class of chemicals, known as pyrethroids, found in common anti-lice shampoos. Worldwide, Koehler said, head lice outbreaks have increased significantly in the past five years as a result of lice adapting to the chemicals, which have been on the market for about 20 years.

He said prescription treatments contain the same chemicals, but the concentration is about five times greater, and the treatments appear to be effective at such high levels.

“If you want to make sure you’re going to kill all the lice the first time, you’d better get the prescription product,” he said.

Hardwick-Allen noted that many parents are fearful of using chemicals on their children’s heads. She and Scherer recommended a comb produced by the National Pediculosis Association, a nonprofit organization dedicated to head lice and scabies prevention and treatment. They described the comb, called the LiceMeister, as a laborious but effective method to remove lice and eggs, known as nits, from a child’s hair.