Are scented candles bad for you to breathe?

The US Environmental Protection Agency lists burning candles among the sources of particulate matter indoors, alongside cooking, heating and smoking, and its advice is short: "Ensure proper ventilation is available when burning candles and incense indoors" (EPA, updated 10 Mar 2026). It also notes that candles can release carbon monoxide and other combustion byproducts.

So the honest question is not whether a candle puts anything in the air. It does. The question is how much, what changes the amount, and when it is worth caring about.

What a candle puts in the air

A flame burns wax, and burning anything produces fine particles. Combustion also makes gases: carbon dioxide and water when it burns cleanly, and carbon monoxide, nitrogen dioxide, formaldehyde, acrolein and polycyclic aromatic hydrocarbons (PAHs) when it does not.

The most thorough measurement comes from a 2021 study in Environment International that burned palm, paraffin, soy and stearin candles, scented and unscented, in a test chamber for seven hours at a time. For most of what it measured, the indoor levels it calculated were well below health guideline values. The exceptions were nitrogen dioxide in short-term scenarios, acrolein, and benzo[a]pyrene, a PAH, which was detected in 5 of 24 tests. The study was funded by the European, US and Latin American candle associations, two of its five authors work in the candle and fragrance industry, and it compared the waxes side by side under the same conditions.

What fragrance adds

That same study found the biggest difference was not the wax. It was the scent. Unscented candles gave off roughly 70 to 200 micrograms of volatile organic compounds per candle per hour. Some scented candles gave off up to about 14,400. The authors' conclusion: "candles without fragrance additives produce lower emissions of combustion by-products than candles with fragrance."

"Fragrance" on a label can stand for a long list of undisclosed ingredients, which is the fragrance loophole, and it works the same way on a candle as on a cleanser. Dr. Meredith McCormack, who directs pulmonary and critical care medicine at Johns Hopkins, put it plainly to the Associated Press (13 Dec 2025): "Clean air is fragrance free."

Ventilation is the variable that matters most

A study published in Toxics on 27 June 2026, from researchers in Tainan, Taiwan, burned a paraffin candle scented with lavender oil in a chamber and changed one thing at a time. At half an air change an hour, the lowest airflow tested, total PAHs averaged 2,799 nanograms per cubic meter. At one and two air changes an hour they dropped to 1,112 and 1,218. The toxicity-weighted measure fell as airflow rose.

The researchers also modeled a deliberately heavy scenario: an aromatherapy worker exposed 8 hours a day, 250 days a year, for 40 years, in the least ventilated room. The highest lifetime lung cancer risk estimate was about 1.2 in a million, just above the 1 in a million benchmark regulators commonly use. The average estimates were lower. One candle formulation was tested, so the numbers are a guide, not a rule for every candle. The conclusion that travels: open the window, or run the fan.

Four things people assume about candles

1. Soy wax doesn't pollute

Unscented palm, paraffin, soy and stearin candles behaved very similarly in the 2021 Environment International study, and none was consistently cleaner. Beeswax was not tested. Experts the AP spoke to made the same point: all lit candles release pollutants, whatever the wax, so soy wax does not remove emissions.

2. A wax melt is clean because there is no flame

Wax melts have no flame, but a team including Purdue engineers found that the fragrance compounds they release react with ozone indoors to form nanoparticles, at levels comparable to scented candles and gas stoves (Environmental Science & Technology Letters, 2025). "Fragranced products are not just passive sources of pleasant scents," said Nusrat Jung, one of the engineers on the study. What those particles do in the lungs has not been worked out yet.

3. Unscented candles don't emit anything

Unscented candles emitted far fewer volatile organic compounds, but they still burn, and nitrogen dioxide from a flame is largely unavoidable, according to the 2021 study's authors. Fewer emissions is not zero.

4. Opening a window makes a real difference

In the Toxics study, total PAHs at half an air change an hour were more than double the level at one or two air changes. That is the single biggest lever a household controls, and it costs nothing.

Who should be more careful

The AP's reporting notes that indoor pollutants are a bigger hazard for children, older adults and anyone with a heart or lung condition, including asthma. The advice from the experts it interviewed: if anyone starts coughing, gets short of breath, or has a headache, a runny nose or sneezing, put the candle out or ventilate the room right away. They also suggested choosing products with fewer ingredients, opening windows when the weather allows and running a HEPA air purifier. If someone in the house has asthma, their doctor is the right person to ask about candles and wax melts specifically.

The bigger risk is fire

Candles caused 2% of reported US home fires, 3% of home fire deaths and 6% of home fire injuries, according to National Fire Protection Association figures for 2015 to 2019 published by the Illinois State Fire Marshal. On average, 20 home candle fires were reported a day. In 60% of them, something that could burn was left or came too close to the flame, and 37% started in bedrooms. December and January are the peak months, at 11% each.

The fire marshal's list is the practical part:

1. Keep candles at least 1 foot from anything that can burn.
2. Blow them out when you leave the room or go to sleep, and avoid them in bedrooms.
3. Never leave children alone in a room with a burning candle, and keep matches and lighters up high.
4. Use a sturdy holder that will not tip, and put the candle out before the flame reaches the holder or container.
5. Consider battery-powered flameless candles, many of which look and smell like the real thing.

Lead is the one wick problem that has been dealt with by law. The Consumer Product Safety Commission banned candles with lead-cored wicks in 2003, after finding that some released lead into the air at rates that could raise a child's lead levels. Since October 2003, a metal wick core sold in the US cannot contain more than 0.06% lead by weight (CPSC).

How to read a candle label

A candle is not a cosmetic, so it does not come with the ingredient list a moisturizer does. The federal label basics for a candle are what it is, how much it weighs and who made it (CandleScience, 2026); an ingredient list is not among them. That makes the label work different from reading a skincare label:

• Is it scented, and with what? "Fragrance" alone tells you nothing more. Unscented is the lower-emission choice, per the 2021 study.
• What is the wick? Most manufacturers use zinc, synthetic fibers, cotton or paper, according to the CPSC. You cannot tell a metal core's material by looking, so the CPSC suggests asking the retailer what the wick is made of.
• Is there a full list at all? Some makers list every ingredient voluntarily. That is a good sign about transparency, not proof of lower emissions.
• Does it carry burning directions and warnings? They are recommended rather than required (CandleScience), so follow them where they appear.

Questions people ask

Are scented candles bad for your lungs?

For most people, an occasional candle in a ventilated room is a small exposure, but it is not nothing. Every lit candle releases fine particles and combustion gases, and a 2021 study found scented candles gave off far more volatile organic compounds than unscented ones. Most measured levels were below health guideline values. Ventilation lowers exposure most, and fire is the clearest risk: about 20 US home candle fires are reported each day.

Are soy candles safer than paraffin?

The evidence does not show a clear winner. In a 2021 Environment International study, unscented palm, paraffin, soy and stearin candles behaved very similarly, and none was consistently cleaner; beeswax was not tested. The study was funded by candle industry associations. Whatever the wax, scent made the bigger difference, and experts interviewed by the AP said soy wax does not remove emissions.

Are wax melts safer than candles?

Not necessarily. Wax melts remove the open flame, but a 2025 study in Environmental Science & Technology Letters found the fragrance compounds they release react with indoor ozone to form nanoparticles at levels comparable to scented candles and gas stoves. The health effects of those particles are not yet understood. Ventilating the room helps either way.

Is it safe to burn candles around kids?

With care. Children are more vulnerable to indoor air pollution, so ventilate, burn fewer candles at once and stop if anyone coughs or wheezes. The fire rules matter most: never leave children alone with a burning candle, keep it at least 1 foot from anything that can burn, keep matches up high, and blow it out before bed.