What’s old is new again for some e-cigarette users who can’t seem to kick their nicotine habit.

As the country’s vaping crisis continues to grow, some smokers who picked up e-cigs to break their addictions — including youngsters enticed by fruit and mint varieties — are now putting down their digital devices in favor of their former vices: traditional cigarettes.

Lucas McClain, 21, of Arlington, Virginia, told California Healthline that he started using Juul products in high school as an alternative to cigarettes on the premise that it was a less lethal alternative.

But he bought his first pack of smokes in years last month — and now feels as if he’s going backward.

“Juul made my nicotine addiction a lot worse,” McClain said. “When I didn’t have it for more than two hours, I’d get very anxious.”

For McClain, quitting his Juul might be tougher than not lighting up a traditional cigarette ever again, especially considering that he could sometimes finish a pod in just three hours — putting as much nicotine as a pack of cigs into his system during that span.

McClain’s ongoing struggle came to a head as his mother warned him about the mysterious illnesses apparently related to vaping that have killed six people and hospitalized 380 others in 36 states.

That some young smokers are now “going back to the product” they were trying to quit isn’t a surprise, according to Pamela Ling, a professor of medicine at the University of California-San Francisco. But it’s alarming, as tobacco smoke still contains a deadly mix of more than 7,000 chemicals, 70 of which can cause cancer, according to Centers for Disease Control and Prevention data.

Dr. Elisa Tong, an associate professor of medicine at the University of California-Davis, said those who vape should not return to cigarettes as they navigate a way to quit using nicotine altogether — and warned that e-cigarette users may be putting much more of the drug into their bodies than they realize.

“What they’re doing is trying to taper down super high levels of nicotine,” Tong told California Healthline, a nonprofit news service by Kaiser Health News. “Ultimately, manufacturers don’t have a manual on how to quit their devices.”

Seven treatments have been approved by the Food and Drug Administration to quit smoking — including patches and gums, but not vaping, Tong said.

Dr. Amanda Graham at the anti-tobacco Truth Initiative said 41,000 youngsters between the ages of 13 and 24 have signed up for a digital program to help them stop vaping since “This Is Quitting” was launched earlier this year.

Graham said she has witnessed “desperation and misguided approaches” from many young smokers as they try to kick their habit once and for all — including those who return to combustible cigarettes, like McClain.

“Young people are fumbling in the dark with what seems logical,” Graham said. “But there is no safe level of cigarette smoking.”

A spokesman for Juul said the device is not intended as a way for people to kick their addiction to nicotine but can help “adult smokers switch from combustible cigarettes to an alternative nicotine delivery system,” according to a statement to California Healthline.

The statement by Juul spokesman Ted Kwong did not address the move by McClain and others to revert to traditional cigarettes, according to the outlet.

Another young smoker, meanwhile, said he tossed his Juul in the trash earlier this month after having strong chest pains and breathing problems when he exercised.

Ryan Hasson, 25, of New York, said he never had that type of pain when he smoked cigarettes and would now turn to burning tobacco rather than buying a Juul pod if he had to do it again.

“I think a lot of people are quitting completely or going back to cigarettes,” Hasson said. “They’re waking up to the reality that maybe this isn’t as safe as we once thought.”