How Long Is Too Long To Keep A Candle Burning? Toxicology Experts Weigh In

Candles made from petroleum-derived paraffin wax tend to be worse for air quality (and the planet) than ones made from cleaner-burning waxes. We recommend opting for candles made from soy or beeswax, scented using naturally derived essential oils, and labeled phthalate-free. (Here are some of our top picks for winter.)

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.