Teens are using vapes in a way that worries doctors. Normally, the devices heat the liquid inside a cartridge or reservoir to produce a vapor that you inhale from the mouthpiece. With "dripping," you put liquids directly onto the e-cig's heating coils, inhaling vapors straight off the heating element. A new survey found that about one in four teens who use e-cigs has tried dripping.

For a study in the journal Pediatrics, Yale researchers surveyed 1,080 e-cigarette users at eight southeastern Connecticut high schools about their vape use and found that 26 percent of them had tried dripping. (They polled more than 7,000 students total then asked more questions of those who had vaped.) The students said they liked dripping for a few different reasons: It produces a thicker cloud of vapor (64 percent), a more pleasurable taste (39 percent), and a stronger throat hit (28 percent). About a quarter of the drippers said they were just curious about it.

It's the first study to look at dripping rates among teens, but it didn't assess how often they did it. The authors did note that students who were male, white, and who used e-cigs more often than others were more likely to have tried dripping.

They don't know exactly how much worse for you dripping is compared to plain old vaping, but previous research suggests that dripping heats the liquid to a higher temperature than the intended use, possibly increasing exposure to formaldehyde, acetaldehyde, and acrolein in the vapors. That's to say nothing of heating the chemicals used to create vape juice flavors like watermelon mojito and blue razzle berry at higher temperatures than intended. There's also the risk of absorbing toxic levels of nicotine from handling the stuff (your skin absorbs it rapidly). Drippers are more likely to have incidental skin exposure compared to people who only bust out their liquid once their reservoir is empty, or use pre-filled cartridges.

While more and more evidence suggests that vaping is less harmful than smoking cigarettes, it's still not risk-free. A recent study published in Annals of Internal Medicine found that smokers who used e-cigarettes or nicotine replacement therapy for six months had significantly lower levels of tobacco-specific chemicals called N-nitrosamines (TSNAs) and volatile organic compounds (VOCs) in their saliva and urine than people who kept smoking or did a mix of smoking and vaping. Lead author Lion Shahab, a health psychology professor at University College London, said in a release: "Our study adds to existing evidence showing that e-cigarettes and NRT are far safer than smoking, and suggests that there is a very low risk associated with their long-term use." That doesn't mean non-smokers should feel free to take up vaping, though, especially teenagers. Nicotine is a neurotoxin and can affect teens' cognitive development and executive functioning.

The authors of the new paper recommend that more research be done and suggest that regulators (read: The FDA) think about imposing restrictions so the devices can't be modified for alternative uses like dripping. The FDA banned the sales of e-cigs to minors in August, but not before they became the most commonly used form of tobacco among American teens, surpassing cigarettes, cigars, chewing tobacco, and hookahs. In December, US surgeon general Vivek Murthy called e-cigs a public health threat for young people.