When used sparingly—say, lighting a candle once or twice a week in a well-ventilated room—the worries are negligible, says Heather Patisaul, PhD, a toxicologist and associate professor of biology at North Carolina State University.
But if you’re firing up multiple scented candles on a daily basis—and especially if you’re doing that in a small space, like a bathroom with the door closed—there’s reason to reconsider your habit, she says.
Here are three ways your scented candles may be messing with your health, and how to dodge the dangers if you’re intent on burning them.
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Many scented candles are made from paraffin, a material derived from crude oil, coal, or shale. Paraffin can contain chemicals like benzene and toluene, Patisaul says. Both make the American Cancer Society’s list of known or probable carcinogens.
Also, Patisaul says the fragrance added to scented chemicals may contain phthalates—a category of endocrine-disrupting chemical that may cause or promote cancer and fertility issues.
Finally, an Environmental Protection Agency report finds “burning several candles” exposes you to levels of formaldehyde and acetaldehyde that exceed the agency’s safety limits when it comes to cancer risk. (Check out these 7 plants that actually purify indoor air.)
A study from the American Chemical Society found the chemical pollutants in paraffin wax candles may cause problems for people with allergies or asthma. Even unscented paraffin or soy-based candles can produce pollutants that could worsen indoor air quality and cause breathing problems, found a study from South Carolina State University.
A study from the University of Michigan found some candle wicks contain lead, which—when burned for more than two hours—could cause lead poisoning in adults. The smoke produced from lead wicks can also coat furniture or carpets, much like secondhand tobacco smoke, and could harm the health of kids, says Jerome Nriagu, PhD, an environmental health scientist at Michigan and author of the lead study.
The good news: Nriagu says that, following his study, new public health regulations banned the use of lead in candle wicks. But if your candles were made prior to October 2003, they could contain lead. So, go scour your cabinets, closets, and storage bins for ancient candles you stashed away for eventual use—they’re not worth the risk.
Patisaul says pure beeswax candles may pose fewer threats than paraffin wax. The authors of that American Chemical Society study agree, and say beeswax provides the same ambience and warmth as paraffin candles without the health risks. Bonus: They emit a natural, subtly sweet smell without any of the dangerous added fragrances. (And look! You can make your own beeswax candles in your slow cooker.)
If you’re not into beeswax, keep in mind that occasionally firing up a paraffin candle in a well-ventilated room is not linked to any health issues. The problem comes from regularly burning several of these candles, or lighting one in a tight space.