High school administrators across central Ohio are increasingly warning parents about teens using e-cigarettes or vapes.

Battery-powered vaporizers allow youngsters to inhale vapors from nicotine mixed with liquids in flavors such as bubblegum, cookies-and-cream or Mountain Dew. They also can be used to inhale marijuana and other drugs.

It’s illegal for unaccompanied minors to use or possess the devices, but high schools and some middle schools across the country have been updating tobacco policies to prohibit e-cigarette use on school property.

At Licking Valley High School in Newark, Ohio, Principal Wes Weaver said confiscations of e-cigarettes have grown from about two or three a year to at least a couple a month.

“We’ve seen a marked increase in students who are using those or possessing those at school,” he said. “It’s just everywhere.”

In February, Granville High School principal Matt Durst used a weekly newsletter to tell parents specifically about the Juul brand of e-cigarette, which looks like a USB storage device and can be charged by plugging it into a USB port.

It’s a different look from bulky, box-like vaporizers or the more slender versions that resemble traditional cigarettes, and it’s a lot easier to hide in plain sight. Further challenging administrators, the device produces odors like the flavoring used, not like smoke. And the vapors don’t linger as long as smoke would.

On Feb. 17, Big Walnut High School in Sunbury, Ohio, sent out a tweet linking to a newsletter about the Juul. A similar message was recently sent to parents, faculty and staff members by New Albany High School principal Dwight Carter. And in September, Ken Nally, assistant principal at Worthington Kilbourne High School, sent parents a newsletter informing them of the vaping trend.

“More kids think it’s OK to vape than ever thought it was OK to smoke cigarettes,” Nally said. “It’s just a battle.”

According to the 2014 Ohio Youth Tobacco Survey, nearly 41 percent of high-school students had tried e-cigarettes, compared with 7.7 percent in 2010. In 2014, nearly 22 percent of high schoolers were current users, meaning they had used the devices within the previous 30 days.

Teens are smoking e-cigarettes at a rate higher than young adults and adults, of whom 5.7 percent are current users, said Mandy Burkett, director of the Tobacco Program at the Ohio Department of Health.

A number of youngsters, and some parents, don’t see the harm in e-cigarettes because they don’t contain many of the carcinogens found in traditional cigarettes. And some vape the flavors only, without added nicotine.

A report released in January by the National Academies of Sciences, Engineering and Medicine found conclusive evidence that replacing traditional cigarettes with e-cigarettes reduces a user’s exposure to numerous toxicants and carcinogens.

However, the report also found that most e-cigarettes emit potentially toxic substances. And it found substantial evidence that use of e-cigarettes by youth and young adults increases the risk that they will at some point use traditional cigarettes.

That concerns Dr. Judith Groner, a Nationwide Children’s Hospital physician who chairs the American Academy of Pediatrics section on tobacco control. Nicotine use in the short-term, she said, can cause cardiovascular issues. In the long-term, it can lead to increasing levels of addiction most easily satisfied by smoking traditional cigarettes. Once a brain develops an addiction pathway, Burkett added, teens are more susceptible to becoming hooked on other drugs.

Additionally, Groner said, flavorings, which are approved by the FDA for use as food additives, have not been tested for safety if inhaled.

Charlotte Hickcox, statehouse lobbyist for the Ohio Vapor Trade Association, said the typical vapor store customer is not a teenager but someone who has used traditional tobacco products in the past and has made a decision to switch to a non-combustible form of nicotine delivery. Vapor stores across Ohio agree that minors should not be vaping, she said, and make it a practice to keep minors out of stores.

Administrators say that underage students are getting the devices from older students.

Administrators updating handbooks try to stay broad enough to include various types of vaporizers and, hopefully, stay a step ahead of technology, said Tim Freeman, a retired high school principal who serves as associate executive director of the Ohio Association of Secondary School Administrators. At a January handbook conference, he said, e-cigarettes were a hot topic.

But administrators and health officials are fighting a tobacco industry that spends about $1 million a day on advertising and promotions in Ohio, Burkett said. That compares to the health department’s $2 million annual budget for counter-advertising measures.

While traditional cigarettes have become largely socially unacceptable among teens, the concern now is that “all the cool kids have a vape,” Freeman said.

— JoAnne Viviano writes about health and medicine for The Columbus (Ohio) Dispatch. Email her at jviviano@dispatch.com or follow her on Twitter at @JoAnneViviano.