According to a recent New York Times investigation, research shows2 that burning a candle at home is unlikely to emit enough particulate matter to harm health. However, Adler points out that indoor air pollution is always more of a concern during the winter months, “when we tend to keep our windows closed throughout the day.” So if you notice that you have an irritated, itchy throat, watery eyes, or headache after lighting up a scented candle, it’s a sign to blow it out and switch to an unscented option. (Adler vouches for small, unscented beeswax tea lights.) Beyond that, it should be safe to burn for up to four hours with a window cracked open as an extra precaution. (Toxicology experts recommend opening windows from time to time in winter anyways, to keep indoor air from getting too stuffy.) After four hours, manufacturers note that most candles will begin to lose their scent. Candle wicks will also begin to mushroom, which can lead to an uneven burn. Adler notes that even the cleanest-burning candles can aggravate those with sensitivities. “All candles, regardless of whether they have additive colors or scents, and whether those scents are synthetic or natural, produce particulate matter when burned,” she says. “Even in the absence of phthalates, many compounds used in fragrance formulations are allergens and can act as asthma triggers.” For this reason, it’s important to pay attention to how your body feels when a candle is burning. To minimize the risk of a reaction, you can open more windows, place the candle further away from you, or move to a larger room with better ventilation. Molecular toxicologist Rhea Mehta, Ph.D., previously told mbg that the smoke that comes from a candle after you blow it out can be especially high in particulate matter. She recommends putting the candle next to an open window after you blow it out to let the smoke escape—especially if you’re about to go to sleep. Emma received her B.A. in Environmental Science & Policy with a specialty in environmental communications from Duke University. In addition to penning over 1,000 mbg articles on topics from the water crisis in California to the rise of urban beekeeping, her work has appeared on Grist, Bloomberg News, Bustle, and Forbes. She’s spoken about the intersection of self-care and sustainability on podcasts and live events alongside environmental thought leaders like Marci Zaroff, Gay Browne, and Summer Rayne Oakes.
