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Candles release particulate matter and other compounds as they burn, but experts cited in a Good Housekeeping report say studies of typical household use generally find emissions below levels of concern. The health risk from a particular exposure is not settled; ventilation and limiting exposure are sensible precautions, especially for people with asthma or allergies.
A Good Housekeeping report on scented candles and health finds that candles release smoke, particles and chemical compounds into indoor air, while experts say studies modeling typical household use have generally measured emissions below levels of concern. Researchers have not established a precise exposure threshold at which candle use causes harm, so ventilation and the amount of burning remain relevant.
Meghan E. Rebuli, a respiratory toxicologist and assistant professor of pediatrics at the University of North Carolina at Chapel Hill, told Good Housekeeping that potential emissions include soot, particulate matter and volatile or semi-volatile organic compounds. She said studies designed to resemble normal household use have mostly found these emissions below levels of concern, regardless of candle type, while some candles—particularly paraffin-based or fragranced ones—may produce more of certain pollutants.
Daniel Croft, an associate professor of pulmonary and critical care medicine at the University of Rochester Medical Center, said exposure depends on several factors: how many candles are lit, their size, how long they burn and the size of the room. He said research links long-term inhalation of particulate matter generally—not necessarily from candles specifically—to asthma attacks, worsening COPD and cardiovascular and neurological harms. The candle-specific question is whether the amount released is enough to cause harm, which remains unsettled.
The report also cites a 2025 study that found burning scented candles led to an increase in certain strains of airborne bacteria. That finding does not by itself establish a health effect. A 2021 study of five types of pillar candles measured emissions over six hours; Croft said emissions appeared higher when burning began and later became relatively stable. The report does not provide a single safe number of candles or a room-size threshold.
How Candle Use Affects Indoor Air
The practical issue is cumulative exposure: emissions can build in a small or poorly ventilated room, particularly when several candles burn for a long time. Croft told Good Housekeeping that ventilation is the most important factor for indoor air quality. Opening a window or otherwise bringing in fresh air can reduce the concentration of pollutants, though the report does not quantify how much ventilation is needed for a given candle or room.
People with asthma or allergies, and pregnant people, may want to be more cautious about avoidable air pollution exposures, the experts said. This is not evidence that ordinary candle use is known to harm these groups; it is a reason to pay attention to symptoms and reduce exposure if needed. The available findings do not support a blanket conclusion that all scented candles are dangerous—or that every product and setting carries the same risk.
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What Candle Studies Have Measured
The report describes a body of research that measures emissions under particular conditions, rather than establishing a universal health limit for candle use. In a 2021 study, researchers examined ultra-fine particle emissions from five pillar candles during a six-hour period. Croft said the paraffin candle had some of the higher emissions in that example, but the types tested showed relatively similar ranges. Earlier research had raised concerns about paraffin, he said, so choosing another wax is an option for people wishing to limit potential exposure while evidence remains incomplete.
A separate 2023 study by the Research Institute for Fragrance Materials assessed consumer exposure to fragrance materials in air, according to Nikaeta Sadekar, a senior scientist at the institute. She told Good Housekeeping that, from the institute’s assessment, there was no concern about risk of harm from exposure through burning candles. That is an attributed expert view and does not resolve every question about emissions, individual sensitivity or different conditions of use.
“Ventilation is absolutely the most important factor when we think about indoor air quality.”
— Daniel Croft, associate professor at the University of Rochester Medical Center
The Exposure Threshold Is Unknown
Experts have not determined how many candles, burned for how long in a room of a particular size and ventilation level, would create a harmful exposure. The report says there is no established danger threshold that can settle the question for every household. Study results also vary by candle type and testing conditions, and the 2025 finding about airborne bacteria does not establish whether the increase causes illness. Individual responses may differ, especially among people with respiratory sensitivities.
Practical Steps While Evidence Develops
The report does not identify a forthcoming study or regulatory decision that will settle the issue. For now, experts recommend paying attention to room ventilation and limiting the number and duration of candles, especially in enclosed spaces. People who notice irritation, coughing or other symptoms can stop burning the candle and air out the room. Those with asthma, allergies or pregnancy-related concerns can discuss persistent symptoms or exposure questions with a health professional. More research would be needed to define candle-specific exposure limits and compare products under consistent real-world conditions.
Key Questions
Are scented candles proven to be harmful?
No. The report says studies resembling normal household use have generally found candle emissions below levels of concern. Experts also say the evidence has not established a precise threshold for harmful exposure, so that does not prove every candle or use pattern is risk-free.
Do scented candles release pollutants?
Yes. Burning candles can release soot, particulate matter and volatile or semi-volatile organic compounds. The amount depends on factors including candle type, number, burn time, room size and ventilation.
Should people with asthma avoid candles?
The experts cited do not say that everyone with asthma must avoid candles. They advise people with asthma or allergies to pay closer attention to air pollution exposures and reduce them where practical, including by ventilating the room and stopping use if symptoms occur.
Are paraffin candles riskier than other candles?
Some research suggests paraffin candles may emit more of certain particles, but Croft said one 2021 comparison found relatively similar emission ranges across the five pillar candles tested. The evidence described in the report does not establish a definitive ranking of all candle types.
What can I do to reduce exposure while burning candles?
Use fewer candles, avoid long burns in small enclosed rooms and improve airflow or ventilation, such as by opening a window when appropriate. The report does not give a universal safe burn time or candle count.
Source: goodhousekeeping.com
