At first, Geri Sullivan didn't think much of the vape pen she found in her son's laundry.

"He would say 'it's just mango, mum. It's just vapour,'" she recalls. "'There's no harm in it. It's not like cigarettes.'"

Her son, Eddie, bought the pen from a service station known to sell to minors as the vaping craze swept over his high school football team. He was never heavily into the habit, which involves inhaling heated up e-juice sometimes mixed with nicotine.

He quit vaping altogether in June, a year after he started. Proud of his number 55 jersey, he hoped to make the cut in his senior year as an offensive lineman.

Instead, he woke up with a fever in late August, two months after he put down the pen.

As he developed new symptoms, including vomiting and extreme pain, Geri took him to the local hospital, where he was diagnosed with pneumonia and put on antibiotics.

Eddie started vaping after the craze swept over his high school football team. ( Supplied )

Over the next week, the symptoms worsened, spreading to his chest.

He felt like he couldn't breathe, then like he was drowning.

This strong American football player was left so weak that his mother had to help him walk as they travelled to another hospital for a second opinion.

As nurses measured the oxygen levels in Eddie's lungs, Geri's fear skyrocketed.

"I remember the nurse saying to him, 'Eddie, put the pulse sock on your finger,'" she says. "He said, 'it is on my finger.'

"There was a look of panic on the two nurses' faces."

He was taking in so little oxygen that the pulse hadn't registered.

Eddie was rushed to intensive care as his doctors struggled to make sense of the puzzling symptoms.

At one point, they asked Geri to leave so they could "ask teenage questions".

That's when Eddie told doctors he'd been vaping.

Eddie, in his number 55 jersey, had hoped to become an offensive lineman for senior year. ( Supplied )

The mysterious vaping illness is becoming a US epidemic

Eddie is just one of 530 people who've been hospitalised from vaping in America over the past month.

At least seven have died because of the mysterious vaping-related illnesses, which are now the subject of a US federal criminal investigation.

What is vaping? Vaping is inhaling the vapour created by an electronic cigarette (e-cigarette) or other vaping device

Vaping is inhaling the vapour created by an electronic cigarette (e-cigarette) or other vaping device E-cigarettes are battery-operated devices that heat an e-liquid to produce a vapour, or an aerosol, that can contain nicotine, flavour and other chemicals

E-cigarettes are battery-operated devices that heat an e-liquid to produce a vapour, or an aerosol, that can contain nicotine, flavour and other chemicals E-cigarette users inhale the vapour in the same way as smoking a cigarette

E-cigarette users inhale the vapour in the same way as smoking a cigarette In Australia it is illegal for retail outlets to sell nicotine e-cigarettes or liquid nicotine for vaping

In Australia it is illegal for retail outlets to sell nicotine e-cigarettes or liquid nicotine for vaping It is also illegal to buy nicotine e-cigarettes or a liquid nicotine for personal use without a medical prescription

It is also illegal to buy nicotine e-cigarettes or a liquid nicotine for personal use without a medical prescription It is easy to access nicotine for vaping from online sellers from outside Australia

Eddie's diagnosis was finally changed to pneumonitis — a fancy word for an inflammation of the lungs caused by exposure to a toxic substance.

He was one of the first patients identified in the epidemic, leaving little in the way of clues for Dr Aaron Chidekel of the Nemours Alfred I duPont Hospital for Children.

"When you have no idea what the cause is, how do you treat it?," Dr Chidekel says. "That is a daunting question. The clock is ticking, and the person can't breathe. It is life or death."

As well as being deadly, it's highly distressing for the patients. As their lungs get heavier, feeling like a wet sponge, the body fears it is drowning.

"That sets in motion all of the uncomfortable sensations that we get when we're in a swimming pool and trying to make our way to the top a little bit later than we had anticipated.

Eddie, pictured with Geri, who didn't think much of his vape pen when she found it. ( Supplied )

"You can't get enough air, and your tissues are starved of oxygen."

A week after he went to the hospital, Eddie was placed on a ventilator. Geri panicked.

"I remember asking them, 'is he going to recover from this?' Like … I can't lose my son," she remembers. "I lost my husband when my son was one. It's just Eddie and myself. He is my whole world."

One local vape store has noticed a dip in interest

At the nearby Alluring Vapors store in Wilmington, a "40 per cent off" sign hangs on the wall.

The owner, a decade-long vaping enthusiast named Justin Brooks, performs tricks as he whiles away the time without customers. The epidemic has scared them all off.

A former American football athlete himself, Justin says vaping allowed him to quit cigarettes and improve his health. He even competes in vaping teams.

"We like to think of ourselves as the healthier way of life," he says.

Vape store owner and enthusiast Justin Brooks says vaping allowed him to quit smoking. ( ABC News: John Mees )

"We always look down on people who smoke cigarettes […] vaping is its own little community for sure."

Brooks blames the epidemic on black-market operators selling cheap, home-made cartridges of nicotine and THC, the active ingredient in marijuana.

"Don't try and skimp and get it off the streets and save $US10, and then ruin both your lungs and then be screwed for the rest of your life," he says. "Doesn't seem like the smart alternative."

Vaping simply hasn't been around long enough for long-term health studies to track users.

The mysterious cluster of illness is giving new scrutiny of an increasingly powerful industry with lobbyists in both the US and Australia.

Vape marketing tactics are under fire

A particularly hot topic is the promotion of colourful, candy-flavoured products, which may be designed to hook a new generation on nicotine rather than wean older smokers off destructive cigarettes.

"The perception that these are somehow safe is a total farce," Dr Chidekel says.

"Breathing a super-heated, complex mixture of gasses — what could possibly go wrong there, right?"

He despairs that rates of nicotine addiction among American teenagers are again rising, driven this time by vaping rather than cigarettes. Estimates for 2019 suggest 25 per cent of North American high school students use vape pens.

Dr Aaron Chidekel said Australia could be the site of the next epidemic. ( ABC News: John Mees )

"Anything we can do to limit the desirability or the normalcy of these toxins and the use of these substances is so important from a public health standpoint," he says.

In Australia, it's legal to purchase e-cigarettes and e-liquid, but only if the products don't contain nicotine.

Consumers buy nicotine on the black market or import it from New Zealand, China and the United States and mix it themselves.

Americans offer a warning to Australian vape users

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Dr Chidekel is warning Australia that it could be the site of the next epidemic if it does not resist a push from the vaping industry to make its products easier to access.

"This is a chemistry experiment, and it's a dangerous experiment," he says. "If this vaping-associated pneumonitis has taught us one thing, it's that this is a dangerous mix."

Eddie spent weeks in the hospital on assisted breathing devices, but his lungs finally began to heal. His life was saved.

It'll take at least until the end of October before his lungs are safe, and he'll be at risk for the rest of his life.

"One of his attending doctors who spoke with us here did not sugar-coat anything with us," Geri says. "He said to Eddie, 'you can never inhale anything again. It doesn't matter if it is a vape, a Juul, a cigarette, whatever. Because you will die.'"

Geri says she wants Australian parents to know that vaping is not the safe alternative that marketing suggests.

"If sharing my story can help one person's life, then it's totally worth it," she says, hugging her son close.