Scented candles, diffusers, and room sprays release invisible particles and gases into your indoor air that you breathe in regularly, including volatile organic compounds (VOCs) and nanoparticles that can affect respiratory health. While the pleasant aroma might feel harmless, researchers have documented over 2,500 chemical ingredients used in fragrances, many of which have potential health implications, especially with frequent and long-term exposure.

What Chemicals Are Actually in Your Scented Candle?

When you light a candle or use a room spray, you're introducing two main types of airborne pollutants into your home: volatile organic compounds and ultrafine particles. VOCs are gases emitted from liquids and solids, and they include chemicals like benzene, toluene, formaldehyde, and acetaldehyde. These same compounds are found in paraffin candles, air fresheners, cleaning supplies, gas stoves, paints, and new flooring.

"Exposure to VOCs can impair lung function and increase inflammation of the respiratory tract lining," said Manu D. Kaushal, a pulmonologist at MedStar Health in Olney, Maryland. "Common symptoms of this include coughing, throat irritation, wheezing and shortness of breath."

Manu D. Kaushal, Pulmonologist at MedStar Health

The second concern involves nanoparticles, also called ultrafine particles. These form when chemical vapors like VOCs react with ozone, a gas present both outdoors and indoors. For example, essential oil diffusers emit terpenes, which are aromatic VOCs found in plants such as limonene and alpha-pinene. When these react with indoor ozone, they create secondary pollutants including formaldehyde and ultrafine particles.

Who Is Most at Risk from Candle Emissions?

People with preexisting respiratory conditions face heightened vulnerability. Those with asthma and chronic obstructive pulmonary disease (COPD) are particularly susceptible to the effects of VOC exposure. Chronic exposure to VOCs may contribute to the onset or progression of asthma, increased risk of COPD, chronic bronchitis, recurrent respiratory infections, and a decline in pulmonary function.

Long-term exposure to certain VOCs has also been linked to additional health effects including cancer formation and issues with hormone signaling, metabolism, and fertility. However, most of these studies have examined exposure from building materials, furnishings, carpets, cleaning products, cigarette smoking, and cooking emissions rather than candles or air fresheners specifically.

Research also suggests a link between exposure to fine particulate matter and a higher incidence of cardiovascular disease and respiratory disease, though more research is needed to determine exactly how damaging certain particles might be and in what amounts.

What About Phthalates and Other Endocrine Disruptors?

Beyond VOCs and particles, scented products often contain phthalates, chemicals that interfere with your body's hormone systems. Phthalates, particularly diethyl phthalate and di(2-ethylhexyl), are the primary endocrine disruptors in scented products. These chemicals interfere with androgen and estrogen signaling, alter thyroid hormone metabolism, and disrupt reproductive development.

The challenge is that manufacturers are not required to disclose phthalates on product labels. The U.S. Consumer Product Safety Commission (CPSC) sets requirements restricting lead content in candle wicks, but there are otherwise no ingredient restrictions for these products. The International Fragrance Association (IFRA) maintains research-based standards for fragrance uses, but compliance is voluntary.

How to Reduce Your Exposure to Candle Emissions

• Remove odor sources first: Before reaching for a candle or spray to mask unpleasant smells, try eliminating the source. Take out the trash regularly, clean your refrigerator and discard spoiled food, wash laundry and pet bedding, and check for mold or water damage if the air smells stale.
• Look for phthalate-free products: Purchase scented products that clearly state "phthalate-free" on the label. This is the most direct way to avoid endocrine-disrupting chemicals in your home.
• Avoid specific harmful ingredients: Choose products that state on the label or manufacturer's website that they are free of terpenes (limonene, linalool, pinene), benzene, formaldehyde, and synthetic musk and cashmeran.
• Limit burn time: Cutting down on how long you burn a candle reduces your exposure to potentially harmful VOCs and nanoparticles. Soot production is directly proportional to the length of the exposed wick, so shorter burning times mean less soot and fewer emissions.
• Improve ventilation: Opening windows or using exhaust fans can help dilute indoor pollutants, though outdoor conditions such as pollen, humidity, or outdoor air pollution can sometimes irritate your lungs, eyes, and throat as well.

Are Beeswax or Soy Candles Really Better?

Many consumers assume that candles made from beeswax or soy are safer alternatives to paraffin. While these materials may produce slightly less soot, any burning candle releases VOCs and particulate matter into your home. The wax type alone does not eliminate the fundamental problem of chemical emissions.

Similarly, nonelectric essential oil diffusers and candle melts do not result in fewer VOCs and nanoparticles compared with lighting a candle or using a plug-in scent. In fact, these alternatives have higher concentrations of fragrance chemicals and more surface area of heated wax, which means more chemicals evaporate into the air.

"Researchers have documented more than 2,500 chemical ingredients used to manufacture fragrances. Most have been used for decades. To be clear, their presence does not imply harm," said Marie Bourgeois, a toxicology researcher and associate professor at the University of South Florida's College of Public Health.

Marie Bourgeois, Toxicology Researcher and Associate Professor at University of South Florida's College of Public Health

The key takeaway is that the risk from scented products depends on multiple factors including a product's concentration, frequency of use, ventilation in your home, and your underlying health. Rather than eliminating all scented items, experts recommend implementing practical steps to lower your risk in manageable ways. Almost all scents and odors are the result of VOCs, even if something is marketed as "natural" or "plant-based," but it is possible to create a space that feels clean and inviting while minimizing your exposures.