For more than a decade, vaping has been sold as a safer alternative to smoking cigarettes. But that doesn't mean puffing on an e-cigarette is not without its harms.

In recent years, a growing number of concerns have surfaced over vaping and its potential to disrupt our health. Normal cigarettes are currently a leading cause of cardiovascular disease in the United States, and a new study suggests the effects of e-cigarettes may also travel beyond the lung.

After just one puff, researchers at the University of Pennsylvania found an immediate change in the body's blood vessels and circulation, even when there was absolutely no nicotine present.

"E-cigarettes are advertised as not harmful, and many e-cigarette users are convinced that they are just inhaling water vapour," says radiologist Alessandra Caporale.

"But the solvents, flavourings and additives in the liquid base, after vaporisation, expose users to multiple insults to the respiratory tract and blood vessels."

E-cigarettes essentially work by converting a liquid base into an aerosol that is easily puffed into your lungs. This liquid usually contains some combination of propylene glycol, glycerol, nicotine, water, flavorings, or preservatives. 

To research the health effects of just the vape juice, Caporale and her colleagues examined 31 adults, aged between 19 and 33, who had no history of smoking or overt cardiovascular, respiratory, or neurovascular issues.

Each of these participants was given a vape with a cartridge that contained no nicotine, only a mix of water and propylene glycol or glycerol. Participants were then instructed to take 16 three-second puffs; an MRI was used to examine their blood vessels before and after.

Focusing on three arteries in the leg, heart, and brain, the researchers noticed a lack of constriction in each one by more than 30 percent. On average, their blood vessels dilated 34 percent less than they did before vaping.

By cuffing the leg and then releasing it, researchers also noticed a 25 percent reduction in blood acceleration after vaping, and peak blood flow was reduced by 17.5 percent. At the same time, oxygen levels within these vessels also dropped by 20 percent.

"We did expect an effect, but we never thought the effect was as big as what we found," radiologist Felix Wehrli told Wired. "It's not just a little change we detect - it's a major effect."

It's important to note that the sample size here is small. But the findings do suggest that vaping might be damaging to the inner lining of our blood vessels, known as the endothelium.

Endothelial injury is thought to be a key initiating event in the build-up of plaque in our arteries, and even though the vascular inflammation was short-lived and reversible, it suggests there's something more insidious at play. And it has nothing to do with nicotine.

"The common belief is that the nicotine is what is toxic, but we have found that dangers exist, independent of nicotine," says Wehrli.

"Clearly if there is an effect after a single use of an e-cigarette, then you can imagine what kind of permanent damage could be caused after vaping regularly over years."

While the ingredients in vape liquid might be harmless to eat, when they are heated, they have the potential to turn toxic. Once inhaled, these toxins could then seep into the bloodstream, potentially leading to vascular inflammation or oxidative stress.

Given that vapes have only been around for some 15 years, it's currently impossible to say what the long-term effects are but even the short term effects have only recently been explored.

In 2017, a study on mice found just five minutes of vaping can damage blood vessels, causing stiffness and narrowing.  A year later, researchers noticed a loss of endothelial cell function in the blood vessels of those people who vaped. In fact, the harmful effects they found were similar to smoking tobacco cigarettes.

As of this week, over 150 people in the United States have fallen ill with a severe and potentially dangerous lung injury linked to e-cigarette use. Some of these patients had such bad respiratory failure, they were sent to intensive care and put on ventilators.

The Centres for Disease Control and Infection have now launched an investigation into the cause.

Michael Siegel, a health scientist at Boston University who didn't take part in the research, told Live Science that the new study confirms e-cigarettes seem to cause some dysfunction of the blood vessels, although the effect appears to be short-lived.

"Further research will be needed to determine whether vaping poses a risk of irreversible blood vessel injury," he said.

The findings have been published in Radiology.