Nicotine-free vapes are not harmless. Even without nicotine, the aerosol you inhale contains base chemicals, flavorings, and metal particles that cause measurable damage to your lungs and blood vessels. The harm is less severe than smoking cigarettes, and likely less than vaping with nicotine, but “zero nicotine” does not mean zero risk.
What You’re Actually Inhaling
The liquid in a nicotine-free vape is mostly propylene glycol, vegetable glycerin, or a mix of both, plus flavorings. These ingredients are approved for eating, but “safe to swallow” and “safe to inhale” are very different standards. When heated into an aerosol, these compounds interact with your airways in ways that food-grade testing never evaluated.
The heating coil itself also contributes to what you breathe in. Aerosol analysis of e-cigarette devices has detected chromium, nickel, copper, zinc, tin, and lead. Chromium and nickel levels in some devices matched or slightly exceeded the amounts found in mainstream cigarette smoke. These metals leach from the coil and other internal components every time the device fires, regardless of whether nicotine is in the liquid.
How It Affects Your Lungs
A 2022 study published in Frontiers in Pharmacology tested what happens when human airway cells and live volunteers are exposed to vegetable glycerin aerosol with no nicotine or flavorings. Within one week, volunteers who vaped VG aerosols showed increased markers of inflammation in nasal tissue samples, including elevated levels of proteins the body produces during immune responses and tissue remodeling. Mucus production also increased in all volunteers after just one week.
In lab-grown human airway cells, five days of VG aerosol exposure slowed the beating of cilia, the tiny hair-like structures that sweep debris and mucus out of your airways. The aerosol also impaired a key channel protein responsible for keeping mucus properly hydrated. When that channel stops working well, mucus becomes thicker and harder to clear. This combination of increased mucus production and decreased clearance is the same pattern seen in chronic lung diseases like cystic fibrosis and chronic bronchitis.
Animal studies reinforced these findings. Sheep exposed to VG e-cigarette aerosols for five days developed significantly higher mucus concentrations in their airways and elevated levels of a growth factor in their blood that’s associated with tissue scarring.
Flavorings Add a Separate Layer of Risk
The flavoring chemicals in vape liquid carry their own hazards. Diacetyl, 2,3-pentanedione, and acetoin are all used to create buttery, sweet, or creamy flavors. All three are linked to irreversible lung disease when inhaled over time. Diacetyl is the most well-known: in 2000, workers at a microwave popcorn factory developed bronchiolitis obliterans, a condition where the smallest airways in the lungs become permanently scarred and narrowed, after breathing in aerosolized diacetyl on the job.
Cinnamaldehyde, the compound that gives cinnamon-flavored vapes their taste, has been shown to impair the function of immune cells in the respiratory tract. A study in the American Journal of Physiology found that flavored e-liquids suppressed the ability of these cells to fight off pathogens. This effect occurred independently of nicotine. Not every flavoring chemical has been tested for inhalation safety, and many vape liquids contain complex blends of multiple flavoring compounds.
Blood Vessel Damage Without Nicotine
One of the more surprising findings in recent research is that nicotine-free vaping causes immediate, measurable changes to your cardiovascular system. A 2025 systematic review in the Journal of Clinical Medicine examined six human studies and found a consistent pattern: healthy volunteers who inhaled nicotine-free aerosol experienced reduced blood vessel dilation, increased arterial stiffness, and signs of oxidative stress.
MRI studies showed that a single session of nicotine-free vaping increased aortic stiffness in healthy people. Other trials found drops in vitamin E levels and reductions in the blood vessels’ ability to relax and expand, a function critical for regulating blood pressure and delivering oxygen. These effects were transient in single-exposure studies, but the review noted that oxidative stress appears to be a central pathway connecting aerosol exposure to vascular dysfunction and inflammatory activation.
Damage at the Cellular Level
Research published in 2025 in Respiratory Research investigated what nicotine-free e-liquid base (propylene glycol and vegetable glycerin alone) does to the cells lining blood vessels in the lungs. The results showed a clear, dose-dependent pattern of harm. As exposure levels increased, mitochondria inside these cells became progressively more damaged. Cells produced more harmful free radicals, lost their ability to generate energy efficiently, and showed signs of a process that leads to cell death.
Specifically, the aerosol triggered the opening of a pore in the mitochondrial membrane that, once opened, collapses the cell’s energy supply and releases signals that initiate programmed cell death. Higher doses of the aerosol meant more pore opening, more energy loss, and more cellular damage. The researchers also found that the aerosol stripped away a protective layer on the surface of blood vessel cells, which could increase permeability and worsen inflammation over time. All of this happened without any nicotine, flavoring, or other additive in the liquid.
The Gateway Question for Younger Users
For adolescents, nicotine-free vapes carry an additional behavioral risk. A longitudinal study tracking teenagers over multiple time periods found that roughly one in seven nicotine-free vapers transitioned to nicotine vaping within each follow-up period. From the first to second assessment, 14% of nicotine-free vapers moved to nicotine products. From the second to third, that figure rose slightly to 17%.
The majority of nicotine-free vapers, around 50 to 54%, actually stopped vaping entirely at each follow-up. So while most teens who try nicotine-free vapes don’t progress to nicotine, the transition rate is not trivial. Fewer than one in ten of the total study population shifted from nicotine-free to nicotine vaping, but for those who continued vaping at all, the pull toward nicotine-containing products was a real and measurable trend.
How This Compares to Smoking
Nicotine-free vaping is almost certainly less harmful than smoking cigarettes. Combustion produces thousands of toxic compounds, dozens of which are established carcinogens, and none of that combustion chemistry applies to vaping. It’s also likely less harmful than vaping with nicotine, since nicotine itself constricts blood vessels, raises heart rate, and creates addiction.
But “less harmful than cigarettes” is a low bar. The research consistently shows that inhaling heated propylene glycol and vegetable glycerin aerosol, even with nothing else added, triggers inflammation in your airways, stiffens your arteries, generates oxidative stress, damages the energy-producing structures inside your cells, and impairs your lungs’ ability to clear mucus. Add flavorings and metal particles from the coil, and the exposure profile grows more complex. The long-term consequences of years of daily use remain unknown, but the short-term biological signals are not reassuring.