The contentious e-cigarette Juul, first released into tobacco markets in 2015, has since exploded in popularity — but not without scrutiny from critics who have deemed e-cigarette use among adolescents an “epidemic.”

As suspicions emerged that Juul Labs has been targeting children with its advertisements, the U.S. Food and Drug Administration raided the company’s San Francisco headquarters on Sept. 28 — seizing thousands of documents related to the company’s sales and marketing practices.

To date, there are no regulations on e-cigarette advertisements in the United States, but in April, the FDA issued warnings to 40 retailers against selling Juul products to underage users.

“There’s some historical advertising that I’ve seen, especially on social media, that gives me pause as to how earnest some of these companies were in making sure that kids didn’t use their products,” said FDA commissioner Scott Gottlieb in a press release.

Despite a federal ban on selling e-cigarette products to minors, many high school students have acquired these devices. Juuls are no exception: Nearly 20 percent of youth aged 12 to 17 have used a Juul, according to a survey conducted by The Truth Initiative, a nonprofit organization dedicated to eliminating tobacco use.

Juuls look like a USB drive and have a sleek, narrow design. As users wrap their lips around the Juul’s mouthpiece and suck in, the device heats up nicotine-containing “e-liquid” and produces a puff of vapor, which is then inhaled by the user.

Each 0.7 milliliter e-liquid cartridge, called a Pod, lasts for 200 puffs and can contain either 3 or 5 percent nicotine by volume. Though these percentages may seem small, Juul pods actually have the highest nicotine concentration of any e-liquid on the U.S. market.

Additionally, the e-liquid also contains flavoring for a more palatable “Juuling” experience. Juul Labs offers several flavors, including “Mango,” “Creme” and “Fruit.”

To scientists, these sweet and fruity additions may be part of the attraction for adolescents. And advertising tactics used by companies such as Juul Labs may only further entice youth to try these harmful products.

A Yale study published earlier this year found that advertisements for flavored e-cigarettes, like Unicorn Milk or Cotton Candy, overrode the negative perceptions associated with tobacco use in a group of adolescents while also undermining the effectiveness of warning labels.

“When you go online to buy an e-liquid, you see an e-liquid bottle with bubble gum behind it, or gumballs, or gummy bears and this is a very typical product placement for buying e-liquid,” said Kathleen Garrison, first author of the study and a School of Medicine professor who works to understand how youth perceive e-cigarette advertisements.

In response to this research, Casy Harper, a spokesperson for Juul Labs, told the News that the company condemns youths’ use of its products, asserting that Juul Labs actively works to discourage adolescent e-cigarette use through initiatives such as educational programs.

“Our goal is to further reduce the number of minors who possess or use tobacco products, including vapor products, and to find ways to keep young people from ever trying these products,” Harper wrote in an email to the News.

Harper did not comment on whether the company intentionally markets its products to minors.

Still, the Yale study was designed before the Juul became a large player in the e-cigarette market, and thus did not cover Juul advertisements, the research highlights a broader problem with e-cigarette advertising.

“You can probably safely say that most, or if not all, e-cigarette companies are using tactics that were previously used [by tobacco companies] to advertise to kids,” Garrison said.

Though tobacco companies once circulated advertisements with appealing cigarette flavors, the government banned this tactic when it was found that flavored cigarettes drew children to smoking. The 2009 Family Smoking and Tobacco Prevention Act banned the sale of cigarettes with “characterizing” flavors other than menthol or tobacco. But the act said nothing about e-cigarette companies who currently use the same advertising methods.

Several organizations such as the American Lung Association and Campaign for Tobacco-Free Kids have sued the FDA for its delay in regulating e-cigarette advertisements. But while the FDA’s September raid of Juul’s headquarters may signal a government crackdown on these companies’ advertising practices, the agency still needs more evidence-based data from researchers like Garrison before it can regulate the industry.

Juul Labs ramped up its government lobbying efforts following the FDA’s September raid of its headquarters, according to a report by The Hill.

Marisa Peryer | marisa.peryer@yale.edu .