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Candles release smoke, particles and chemical compounds, but experts cited in a Good Housekeeping report say studies of typical household use generally found emissions below levels of concern. The health impact depends on exposure, and researchers have not established a candle-specific threshold for harm; ventilation and limiting use can reduce exposure.
A Good Housekeeping report on scented candles says they release smoke and airborne particles, but experts cited in the article say studies of typical household use have generally measured emissions below levels of concern. The evidence does not establish exactly how much candle exposure could cause harm, leaving room conditions and ventilation central to assessing risk.
Meghan E. Rebuli, a respiratory toxicologist and assistant professor of pediatrics at the University of North Carolina at Chapel Hill, said candle emissions can include soot, particulate matter and volatile or semi-volatile organic compounds. Studies that simulated normal household use have mostly found these emissions below thresholds of concern, she said, though paraffin-based and fragranced candles may produce more of some pollutants.
Daniel Croft, an associate professor of pulmonary and critical care medicine at the University of Rochester Medical Center, said exposure depends on factors such as the number and size of candles, how long they burn, and the size and ventilation of the room. The report says researchers have not established a specific threshold defining how many candles, in what size room and without what level of ventilation, would pose a health risk.
The report also describes a 2025 study that found an increase in certain strains of airborne bacteria after scented candles were burned. It does not establish that this finding means candle use causes illness. Croft said research on long-term exposure to particulate matter links it with respiratory and cardiovascular problems, but much of that evidence is not specific to candles.
How Room Conditions Shape Exposure
The findings matter to people who burn candles indoors because exposure is not determined by scent alone. A candle burning for a long time in a small, poorly ventilated room may contribute more to indoor pollution than brief use in a larger, ventilated space. The report does not quantify that difference or define a safe number of candles.
People with asthma or allergies, and pregnant women, are advised by the experts to pay closer attention to potential air pollution and reduce exposures where practical. Croft identifies ventilation as the most important factor for indoor air quality. Opening windows when conditions allow and limiting the number or duration of burning candles are practical ways to reduce emissions in the room.
The overall message is neither that scented candles are risk-free nor that ordinary use has been shown to cause harm. Rather, the available studies described in the report suggest that typical emissions are generally low, while individual sensitivity and cumulative exposure remain relevant.
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What Candle Studies Have Measured
A 2021 study examined ultrafine-particle emissions from five types of pillar candles over six hours. Croft said emissions appeared higher when the candles first began burning and became relatively stable later. In that example, the paraffin candle had some of the higher particle emissions, but the candle types were within a relatively similar range, according to his account.
The report also cites a 2023 study by the Research Institute for Fragrance Materials, which examined consumer exposure to fragrance materials in the air. Nikaeta Sadekar, a senior scientist at the institute, said the institute found no concern of harm from exposure through burning candles. That assessment is an attributed view from the institute; the supplied report material does not provide the study’s methods or results in detail.
These findings do not settle every question about candle use. Studies differ in what they measure, and research on particulate matter’s health effects often concerns broader or longer-term exposures rather than candles specifically. The report says paraffin and fragrance may affect emissions, but does not establish that one candle type is harmful under ordinary conditions.
“The dose makes the poison.”
— Daniel Croft
No Candle-Specific Harm Threshold
Researchers have not defined how many candles or how much exposure would cause harm in a room of a particular size and ventilation level. The supplied report also does not provide enough detail about the 2025 airborne-bacteria finding to determine its health significance, or whether the increase translates into a measurable risk to people.
The evidence on paraffin and fragrance is not conclusive. Some studies suggest these candles may emit more pollutants, while the studies described in the report found typical household emissions generally below levels of concern. The report does not establish a clear risk ranking among candle types or prove that any specific type causes illness during normal use.
Use and Research Remain Key
For now, the experts’ practical guidance is to ventilate rooms, avoid burning more candles than needed, and pay attention to irritation or other symptoms. People with asthma, allergies or pregnancy concerns may choose to reduce potential exposures, including by limiting candle use and opening windows when appropriate.
The report does not identify a forthcoming study or regulatory decision that will settle the issue. A clearer assessment will require research that measures real-world exposures and connects them to health outcomes, including how candle type, burn time and room ventilation affect exposure. Until then, the specific level at which candle emissions become harmful remains unknown.
Key Questions
Are scented candles proven to be harmful?
No. The experts cited in the report say studies simulating typical household use have generally found emissions below levels of concern. That does not establish that every exposure or candle type is harmless.
Do scented candles release pollutants?
Yes. Burning candles can release soot, particulate matter and chemical compounds. The amount a person breathes depends on factors including burn time, candle number, room size and ventilation.
Are paraffin candles worse than other candles?
Some research cited in the report found relatively higher particle emissions from a paraffin candle, but the measured candle types were in a similar range. The evidence does not establish that paraffin candles cause harm during ordinary use.
How can I reduce exposure when burning candles?
Use fewer candles, limit how long they burn and ventilate the room when possible. The report says people with asthma or allergies, and pregnant women, may want to be especially attentive to potential air pollution.
Source: goodhousekeeping.com
