Do Scented Candles Pose a Health Risk? What Specialists Say About the Hazards

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Scented candles can make a gathering feel warm and inviting, or add atmosphere to a quiet evening at home. But if you have ever noticed smoke rising from the flame or soot building up around the glass and wondered whether it is safe to breathe, you are not alone. We asked experts to break down the possible health risks of candles.

Whether they are scented or not, candles release smoke and particulate matter as they burn, which naturally raises questions about indoor air quality.

“Paying attention to the air quality in your home is an important part of staying in good health,” says Daniel Croft, M.D., M.P.H., an associate professor of pulmonary and critical care medicine at the University of Rochester Medical Center. Poor indoor air quality can contribute to symptoms such as irritated eyes, a sore throat, fatigue, headaches, and breathing problems, so it is worth being mindful of the air in your home.

The good news is that you do not necessarily have to give up scented candles entirely. Experts say there are ways to burn them more safely. Here is what they say about the health effects of using scented candles indoors.

Is burning candles dangerous?

The answer is not straightforward. Meghan E. Rebuli, Ph.D., a respiratory toxicologist and assistant professor of pediatrics at the University of North Carolina at Chapel Hill, says possible concerns include inhaling soot from candle smoke, volatile and semi-volatile organic compounds (VOCs), and particulate matter (PM). “A variety of studies that have studied burning candles in an indoor setting that mimics ‘normal’ household use have mostly found that the amount of soot, VOCs, and PM produced are well below the threshold of concern, regardless of the type of candle burned,” she says. “That being said, some types of candles may increase the amount of worrisome chemicals and particles in the indoor space, especially paraffin wax-based candles and fragranced candles. However, levels are not likely of major concern.”

What health effects can candles have?

The possible effects can vary. One 2025 study found that burning scented candles can significantly increase the number of certain bacteria in the air. Most research is not candle-specific, but according to Dr. Croft, studies show that long-term inhalation of particulate matter is linked to asthma attacks, flare-ups of chronic obstructive pulmonary disease (COPD), and a higher risk of cardiac events, stroke, and other neurologic conditions.

“Sometimes you can see visible smoke or soot coming off of the candle so certainly there is some degree of particulate matter that's released into the air,” says Dr. Croft. “I think the big question in the literature is, well, is it enough? Is there too much particulate matter? Is there enough to harm someone? I think the most important thing for consumers and people that are using candles to know is that in toxicology, the dose makes the poison. So, when you think about the emissions from a candle, the number of candles you're lighting, the size of the candle, the duration that it's burning, the size of the room—that would all matter in terms of what the exposure would look like.”

So far, no study has defined a firm danger threshold or determined exactly how many candles in a room of a certain size without ventilation would cause harm. Until that happens, Dr. Croft says people should pay attention to their environment and notice when a candle’s impact may become overwhelming. “Ventilation is absolutely the most important factor when we think about indoor air quality,” he says. A 2021 study found that clearing the carbon dioxide produced by two candles in a room required the same effort as clearing the carbon dioxide exhaled by one 176-pound human. In other words, proper ventilation matters when a room becomes too full of people or too full of candles.

Both experts also say that people with asthma or allergies, as well as pregnant women, should be especially aware of possible air pollution exposures and reduce them where they can, such as by opening windows to improve ventilation.

What about paraffin wax?

A 2021 study examining ultra-fine particle emissions from five kinds of pillar candles, including a paraffin or petroleum-based candle, over six hours found that emissions were higher when the candles first began burning and then became relatively steady later on, says Dr. Croft. “Even though technically, I think the paraffin candle in that example had some of the higher particulate emissions, they all had a similar or relatively similar range,” he says. Still, he notes that earlier research suggested paraffin candles may carry more risk, so it is reasonable to avoid them if you want to err on the side of caution.

Are scented candles worse than other candles?

“We look at the release of fragrance compounds that are embedded into the products to provide scent and we look at how that release determines what kind of exposure consumers are going to have and from there, what kind of effects will they have on their health,” says Nikaeta Sadekar, Ph.D., D.A.B.T., a senior scientist at the Research Institute for Fragrance Materials (RFIM). “So from that perspective, there is no concern of any risk of harm from their exposures by burning candles.”

In fact, a 2023 study by the RFIM found that consumer exposure to fragrance materials through the air, including from scented candles and other fragranced products, is generally very low and well below levels of toxicological concern, Sadekar says. Another widely cited study co-conducted by the RFIM measured the emissions of a scented paraffin candle in rooms of different sizes over four hours and found that some potentially harmful chemicals were released, but at levels less than half of the limits set by the World Health Organization. “Under normal conditions of use scented candles do not pose known health risks to the consumer,” the study authors concluded.

The RFIM has also studied a person’s overall fragrance exposure during the day through products such as lotion, perfume, face cleanser, body wash, shampoo, hand sanitizer, and more. “We calculate those consumer exposures—the aggregated is considering all the different kinds of products together—and so that includes candle use as well,” says Sadekar. “We know that combined, all of those exposures are still very low.”

That said, scent is a personal experience. “Fragrances have a very intimate relationship, I think, with an individual because they help you form memories, they help you form routines, and if you’re using a scented product and you enjoy it, then it truly uplifts your mood,” says Sadekar. “But if a scent you perceive as unpleasant starts to overwhelm your sensory experience, it’s important to either remove yourself from the environment or ask if the scent can be removed or the room ventilated,” she advises. She adds that the feeling is similar to being stuck in a room with music that is too loud: prolonged exposure to something you do not like can eventually make your body signal that you need to leave.

Are candle wicks made with lead?

Not anymore. “In the past, wick type might also have been a concern, but currently in the United States wicks are not lead-based, reducing risk,” says Rebuli.

How to burn candles more safely:

Although candles appear to be relatively safe under normal use, these steps can help reduce possible harm.

1. Use an air purifier. HEPA-based indoor air cleaners are effective at removing particles from the air, says Dr. Croft. But candle combustion also releases gaseous pollutants, which particle filters do not capture. Some purifiers include charcoal filters meant to absorb gases, but those filters must be replaced regularly or they become saturated and stop working well. He also recommends turning off the ionization feature, since it can generate indoor ozone that may irritate the lungs or worsen asthma.
2. Keep the room ventilated. This matters whether you are burning a candle or using a gas stove. “Ventilation is really the way to get rid of gaseous air pollutants within homes,” says Dr. Croft. If a kitchen vent does not exhaust outdoors, he recommends opening a window or using another fan or exhaust system to keep air moving.
3. Choose unscented candles. If certain fragrances bother you, unscented candles may give you the mood you want without as much sensory overload. “Unscented doesn’t mean there are no fragrance components,” says Sadekar. “It’s just that there are components that will mask the un-aesthetic odors of the other components of the raw materials. You will not smell anything good, but you will also not smell anything bad.”
4. Trim the wick before lighting. A shorter wick creates a smaller flame, which can reduce smoke and soot.
5. Do not lean over the flame. It may be tempting to get a stronger whiff of a favorite scent, but putting your head over the candle is not a good idea. “Do not inhale candle smoke directly,” says Rebuli.
6. Use a timer. Rebuli advises against burning candles for extended stretches of more than a few hours, since that can increase exposure to potentially harmful compounds.
7. Blow candles out carefully. “Extinguish the candle with a snuff or by dipping the wick in wax to reduce exposure to soot and smoke,” Rebuli suggests. A metal wick dipper can help, or you can use an old butter knife to push the wick into the wax and then straighten it again.
8. Keep fire safety in mind. Rebuli says burning candles should always be kept in sight and put out before bedtime or before leaving the room.
9. Consider flameless options. If you want fragrance without burning something, an electric wax warmer may be a safer alternative. “I do research on air pollution so the fewer things we can burn, the better so if people can accomplish the same goal without burning something, I'm certainly in favor of that,” says Dr. Croft.

The bottom line:

“Studies are actively underway regarding the emissions from candles and trying to answer these important questions,” says Dr. Croft. “I don't want anyone to think ‘Okay, well it's settled, candles are safe.’ This is an active area of research and it's an area that we all need to follow and while all the research develops, moderation is really key.”