Thanks largely to computing power, genetic engineering, biopharmaceutics, and new technologies, the “precision-medicine” promise of the 2000s is finally here.

A few weeks ago, officials from the Trump administration threatened to ban all flavors of e-cigarettes. Although plans for that regulation are still in the works, some state- and municipal-level bans have already taken effect, or could do so much more quickly.

But if the goal of these regulations is to cut down on teen vaping, there could be a better way: changing the kind of nicotine available in e-juice to make it harder to inhale.

While surveys show that flavors inspired by fruits, cereal, or baked goods are a big draw for high school vapers, it’s the addictive nicotine that will keep them hooked. Over the years, tobacco companies have figured out ways to make the natural nicotine found in tobacco even more potent—and e-cigarette companies have followed suit.

The first trick, discovered decades ago by tobacco companies, is to add a little extra ammonia. This helps free nicotine from its natural chemical constraints, creating so-called “freebase” nicotine that hits the lungs and blood stream faster. The trouble is, it doesn’t feel great to breathe in.

Freebase nicotine is pretty basic, says Thomas Eissenberg, a health psychologist at Virginia Commonwealth University—as in, it has a pH much higher than 7. Regardless of whether a substance is acidic or basic, the farther away from 7 it is, the more corrosive it’ll be; freebase nicotine has a pH of around 9, and household bleach has a pH of about 12.5. While our lungs can take in some freebase nicotine, after a while they need a break.

So the tobacco industry found another way to make nicotine easier to take in: turning it into a salt.

Salts, chemically speaking, are made of two components with positive and negative charges—opposites that attract, keeping them stuck together. In the case of nicotine salts, the nicotine molecule has an extra positively-charged hydrogen ion (or proton) tacked on, giving it a pH closer to neutral 7. This protonated nicotine, used in most cigarettes, will still make you cough, but it goes down smoother.

The first e-cigarettes that hit the market in the mid 2000s contained freebase nicotine—the same harsh substance commonly used in cigars and pipe tobacco. But soon, vape manufacturers started capitalizing on the smoother nicotine salts.

Juul was one of the first companies to get on board. As the Verge reported back in 2018, Juul founders caught wind of the nicotine salt trick as early as 2013—two years before they started selling their e-cigarettes (technically, the first company to use nicotine salts was British American Tobacco, whose vapes are known as Vuse). The startup patented a way to make protonated nicotine with any of a number of carboxylic acids. On its pod ingredient list, Juul states that it uses one called benzoic acid.

That small tweak no doubt helped make e-cigarettes more appealing to all vapers—including young users. Today, surveys show that more than 25% of high schoolers have vaped within the past 30 days, compared with 12% just two years ago. As cigarette smoking among youth dropped off, vaping started to climb.

Eissenberg thinks that it wasn’t the flavors that drew American teens in—although they’re certainly an appeal. Instead, he thinks that the smooth, protonated nicotine is the culprit, because it doesn’t feel like smoking. One study published earlier this year from researchers at Stony Brook University in New York found that some teens didn’t even realize they were vaping nicotine when they were using e-cigarettes.

“Four years ago we had kids using e-cigarettes, but we didn’t have these huge spikes…until Juul started selling their product,” Eissenberg says. The uncomfortably high pH of freebase nicotine means the body can essentially self-regulate how much it takes in at once. “When it was freebase, we didn’t have an epidemic of kids vaping,” he says.

Nicotine salts may also make it easier to sell e-juice with even more nicotine because of its deceptively smooth taste. Prior to Juul, most e-cigarettes contained around 36 milligrams of nicotine per milliliter of vape juice, Eissenberg says. Juul advertises that its pods contain about 59 mg/mL. An independent analysis done by researchers at the American University of Beirut and published in the BMJ journal Tobacco Control, though, found that they actually contained closer to 69 mg/mL.

And that doesn’t account for people vaping knock-off products, or e-juices they’ve mixed themselves that have even higher concentrations of nicotine. The more nicotine in an e-cigarette and the easier it is to smoke, the easier it is for people—particularly new smokers like teens—to become hooked.

But the national conversation around e-cigarette regulations remains focused on banning flavors to deter youth vaping. Many have pointed out why a flavor ban could be a bad idea. It could lead to vapers mixing e-juice at home, with potentially dangerous ingredients; it could lead to vapers hoarding sweet cartridges and selling them at a premium to teens; or it could lead to vapers switching back to smoking tobacco cigarettes in the face of having no good way to quit.

“If the goal is to get kids to stop smoking, one of the first steps should be getting rid of protonated nicotine,” says Eissenberg. “All a regulatory agency would have to do is to pass a regulation that says ‘no e-cigarette liquid sold in the US can have a pH less than 9.'”

It’s not clear when the US Food and Drug Administration, which would be enforcing the national ban on flavored e-cigarettes, will make its decision.