The warm flicker and aroma of scented candles can create an atmosphere of comfort and relaxation. But beneath this cozy feel, scientific research is uncovering a troubling truth: these products are polluting the very air you breathe.

Recent studies have revealed that all scented candles, even “flame-free” scented products—like wax melts—emit nanoparticles comparable to pollution from diesel engines​. They release toxic volatile organic compounds (VOCs), carcinogenic pollutants, and fine particulate matter that can damage your lungs, disrupt your hormones, and even increase the risk of chronic disease​​.

Candles and VOCs

Scented candles are designed to release fragrance but they also release something far more insidious: a cocktail of volatile organic compounds (VOCs). VOCs are the primary culprit behind the pollution caused by scented candles. They’re often found in petroleum-based waxes and synthetic or natural fragrances and they react with indoor air to form secondary pollutants like formaldehyde, benzene, and other ultrafine particles.

Studies have shown that nearly all fragranced products—including “green” and “organic” ones—released at least one hazardous chemical​. These emissions are strong enough to trigger problems even if they aren’t burned: just by being in the room, a scented candle can cause issues.

“I have heard from numerous people who have asthma that they can’t even go into a store if the store sells scented candles, even if they aren’t being burned,” said Anne Steinemann, who led one of the studies, in 2015. “They emit so much fragrance that they can trigger asthma attacks and even migraines.”

Many people turn to soy or beeswax candles as an alternative, assuming they are safer. However, research indicates that even natural waxes release VOCs when burned, particularly if they contain added fragrances​.

Nanoparticles: The Invisible Threat

A 2025 study focused specifically on scented wax melts, which are marketed as a “safe” alternative to traditional candles. The researchers found that these products also release nanoparticles in concentrations comparable to emissions from gas stoves and car exhaust.

These nanoparticles are so small they bypass the body’s natural defenses, often traveling directly from the lungs into the bloodstream. Once there, they contribute to inflammation, oxidative stress, and DNA damage, increasing the risk of problems like cardiovascular disease or lung damage.

Another study examined air fresheners, diffusers, and other room fragrance products. They too release over 100 different chemical compounds​. Among them, terpenes—naturally derived from plant oils—react with indoor ozone, forming secondary organic aerosols and ultrafine particles that degrade air quality. It’s not just the fragrance, either. Notably, the study found that even fragrance-free or “natural” products emitted toxic compounds, challenging the idea that “clean” or essential oil-based products are inherently safe​.

“I think it would be almost impossible to not make some sort of indoor pollution with any type of candle,” said Michael Bergin, a civil and environmental engineering professor at Duke University, for Inverse.

This is particularly concerning for people with a sensitivity to acute toxicity. However, that involves more people than you’d think. A 2019 study, also by Steinemann, found that 20% of the population reports some form of chemical sensitivity, with symptoms ranging from migraines and asthma attacks to neurological impairment​. Around one-third of people report some fragrance sensitivity, and 7.4% of the population report medically diagnosed multiple chemical sensitivity, a condition characterized by vulnerability to pollutants. The study was carried out on participants in the UK, UK, Australia, and Sweden.

Even more troubling, children and pets—who breathe more air per body weight than adults—are particularly vulnerable to these toxins. Babies, whose developing lungs and immune systems are still fragile, are at a greater risk of respiratory diseases when exposed to indoor air pollutants from scented candles and air fresheners.

How Your Home Becomes a Pollution Trap

Unlike outdoor pollution, indoor air pollution from candles and air fresheners is trapped in enclosed spaces, leading to prolonged exposure.

Modern homes are often not sufficiently ventilated because they are designed for energy efficiency rather than air exchange. This makes them more prone to trapping indoor pollutants like VOCs, particulate matter, and carbon dioxide inside. With airtight construction, sealed windows, and improved insulation, homes reduce energy costs but they also limit fresh air circulation.

Many people also rarely open windows, especially in colder months or in urban areas where outdoor pollution is a concern, further reducing airflow. As a result, indoor air pollutants accumulate, creating a stagnant environment where chemicals from candles, cleaning products, and furnishings linger far longer than they would in a well-ventilated space.

If you love scented candles or other similar products, it’s advised you ensure good ventilation inside your home. If you must use candles, an unscented beeswax with a cotton wick tends to burn more cleanly than a paraffin candle.

Now, we should also address the sense of scale. A scented candle won’t kill you, and in fact, one 2014 study reported that under “normal conditions,” scented candles do not pose known health risks to the consumer. However there aren’t enough long-term studies to properly assess this risk, and we do know that VOC pollution can pose health risks.

Ultimately, it’s up to everyone to decide how much they value the indulgence of a scented candle versus the potential risk. But at the end of the day, the science is clear: they are a significant source of indoor air pollution, and the hidden toxins they release linger far beyond the moment they are blown out.

The question remains: is a pleasant aroma worth the long-term health risks?