Hey teens, if you notice your best-friend-forever scratching her head a lot and coming at you with her cellphone, you might want to step away from the selfie. Such is the advice of “lice expert” Marcy McQuillan from San Francisco’s lice-removal salon, Nitless Noggins.

“I’ve seen a huge increase of lice in teens this year. Typically it’s younger children I treat, because they’re at higher risk for head-to-head contact. But now, teens are sticking their heads together every day to take cellphone pics,” McQuillan told SFist.com.

Selfies are fun, but the consequences are real,” she added.

According to the Centers for Disease Control and Prevention (CDC), an estimated 6 million to 12 million lice infestations strike the daycare and primary school set each year in the United States. But could the problem be expanding to older children, thanks to the need to smoosh their heads together, assume proper pouty faces, and take a cellphone snap?

“It's certainly plausible because that's the way head lice spreads,” Nichole Bobo, the National Association of School Nurses’ director of nursing education, told the Chicago Tribune.

Sheila Fassler, an RN and owner of Pediatric Hair Solutions in Atlanta, agrees with McQuillan that the demographic is changing ... and that group selfies are to blame.

“We’re seeing a huge increase in teens and early 20s with head lice here in Atlanta,” says Fassler, who recently treated two university students and two high school students.

“It used to be that head lice occurring in high school and college-age students was rare, but not any more,” she says. “It’s a problem the community needs to know about. Thanks to selfies and all of the daily photo-sharing, it’s not just kids at risk for lice anymore.”

The notoriously tenacious critters that live, dine and raise their brood in the privacy of the human scalp are spread by direct contact with the hair of an infested person. The CDC notes that anyone who comes in head-to-head contact with someone who already has head lice is at greatest risk.

And although teens rubbing their heads together in the pursuit of the perfect selfie seems like lice heaven, other experts are downplaying the risk.

“It’s theoretically possible,” said Shirley Gordon, director of the Head Lice Treatment and Prevention Project at Florida Atlantic University. Yet she says that selfie-induced lice infestation is unlikely. “It’s normally close personal contact, not the few seconds it takes to take a selfie,” she said.

Meanwhile, Dr. Richard J. Pollack from the Harvard School of Public Health has a more emphatic take on the notion.

“This is a marketing ploy, pure and simple,” he told NBC News. “Wherever these louse salons open a new branch, there always seems to be an epidemic. It’s good for business."

“I’m trying to prevent people from overtreating,” he said. “People should not be using insecticides on their kids unless there really is a reason to use them.”

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