Scented candles, air fresheners, and incense sticks don't remove indoor pollutants; they actually add harmful chemicals and particulate matter to your home's air, according to recent research on indoor air quality. While these products are marketed as ways to improve how your home smells, studies show they may be doing the opposite for your health, especially in rooms with limited ventilation.

What Exactly Are Scented Candles Releasing Into Your Home?

When you light a scented candle, you're not just releasing a pleasant aroma. Burning candles and incense sticks produces a complex mixture of chemicals and particulate matter, including toxic gases like carbon monoxide, sulfur dioxide, and nitrogen oxides. Scented candles are particularly problematic because they release volatile organic compounds, or VOCs, which are airborne chemicals that can harm your health with both short-term and long-term exposure.

The problem is compounded by the fact that manufacturers aren't required to disclose all the substances used in scented candles due to patent protections in the United States and European Union. Research estimates that in the US, less than 10% of home fragrance ingredients are disclosed to the public. This means you may have no idea what chemicals you're breathing in when you light that cozy candle.

One particularly concerning finding: scented candles are likely to produce more fine particulate matter than unscented candles. A flickering flame produces larger particles and increases emissions of black carbon, which can penetrate deep into your lungs.

How Much Pollution Can a Single Candle Create?

The scale of pollution from candles becomes clear when you look at the numbers. Research examining Irish homes after energy retrofits found that when scented candles were burned in poorly ventilated spaces, peak fine particle concentrations could increase to 15 times the limits prescribed by the World Health Organization. These elevated pollution levels took a considerable amount of time to return to normal in underventilated rooms.

To put this in perspective, in non-smoking homes, candle use can be the major source of particulate matter pollution. When equal weights of cigarettes and incense sticks are burned, incense sticks produce around four times as much particulate matter as cigarettes. That's a striking comparison that highlights just how significant candle emissions can be.

Aerosol air fresheners introduce fine and ultra-fine particles into home air along with a range of VOCs. Using scented candles or air fresheners in small bathrooms or bedrooms exposes you to much higher concentrations of these pollutants, increasing health risks substantially.

What Health Effects Can Result From Candle Smoke Exposure?

The health impacts of candle emissions span both immediate and long-term concerns. Particulate matter from candles can cause short-term effects like coughing, sneezing, and irritation of the eyes, nose, throat, and lungs. But the risks don't stop there. Long-term exposure to particulate matter increases the risk of heart disease, lung cancer, and chronic bronchitis, and can worsen existing conditions like asthma.

Some of the organic compounds emitted by home fragrance products, such as benzene, phthalates, and formaldehyde, may cause cancer. Burning scented candles and incense sticks indoors is a major source of formaldehyde, and in poorly ventilated rooms, formaldehyde concentrations can reach levels that cause upper airway irritation.

Nitrogen oxides, the most produced gaseous pollutant from scented candles, can have a negative effect on lungs and airways. Air freshener exposure has been associated with negative health impacts including migraines, asthma attacks, and dermatitis. Short-term exposure to candle smoke has even been shown to reduce cognitive function, while chronic exposure to incense smoke has been linked to decline in cognitive functions.

Does "Natural" Mean Safer?

Many consumers purchase home fragrances made with natural ingredients, believing they're avoiding harmful chemicals. However, this assumption may be misguided. When burned, natural home fragrance additives can also release harmful levels of pollution. Some of the chemicals emitted can react with ozone in room air, producing byproducts that may also be toxic. The word "natural" on a candle label doesn't guarantee safety when that product is burned indoors.

How to Reduce Your Exposure to Candle Emissions

• Use candles in larger spaces: Burn home fragrance products in larger rooms like living rooms rather than small bathrooms or bedrooms, where pollutant concentrations become dangerously high.
• Open windows and check vents: Ensure windows are open when using scented candles, and verify that any wall vents in your home have not been blocked, especially in rooms where you plan to use fragrances.
• Snuff candles outdoors: Most of the smoke from candles is emitted when the flame is extinguished, so always try to snuff out candles outdoors rather than inside your home.
• Limit use in poorly ventilated spaces: Avoid using scented candles, air fresheners, or incense in rooms with limited air circulation, where pollutant concentrations can spike to dangerous levels.

What Does the Research Tell Us About the Future?

While the use of home fragrances is on the rise, research on these products remains limited, and scientists don't yet fully understand the extent of their impact on air quality and health. It's also possible that some adverse health effects may only appear after years of chronic exposure to candle emissions and other home fragrance products. The UK home fragrance market generated revenue of approximately $685.5 million in 2023 and is expected to reach approximately $1.2 billion by 2030, suggesting that consumer use of these products will continue to grow.

Part of this growth is spurred by increasing consumer awareness of indoor air quality, yet many people don't realize that scented candles and air fresheners don't actually remove harmful indoor pollutants; they mask odors while adding new chemical pollutants to the air. As research continues, the evidence suggests that if you love using home fragrances, taking steps to reduce exposure through ventilation and careful placement is essential for protecting your respiratory health and indoor air quality.