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A Good Housekeeping report citing respiratory and toxicology experts says burning candles releases particulate matter and chemical compounds, but studies simulating ordinary household use have generally measured levels below thresholds of concern. The health risk for a given person is not settled: exposure depends on factors such as ventilation, room size, candle number and burn time, and a precise harm threshold has not been established.
Burning scented candles releases particulate matter, soot and volatile compounds into indoor air, but studies designed to resemble ordinary household use have generally found emissions below levels of concern, according to experts interviewed by Good Housekeeping. The report says the risk from any particular candle use remains hard to quantify because exposure depends on ventilation, room size, burn time and the number of candles, and researchers have not established a precise threshold for harm.
Meghan E. Rebuli, a respiratory toxicologist and assistant professor of pediatrics at the University of North Carolina at Chapel Hill, said research on candle burning in indoor settings that mimic normal household use has mostly measured soot, volatile and semi-volatile organic compounds, and particulate matter at levels below thresholds of concern. She cautioned that paraffin-based and fragranced candles may produce more concerning emissions, while saying measured levels are not likely to be a major concern in the studies she discussed.
Daniel Croft, an associate professor of pulmonary and critical care medicine at the University of Rochester Medical Center, said the amount of exposure depends on how many candles are lit, their size, how long they burn and the room’s size. Smoke and soot may be visible, but the report says available research has not determined how many candles in a room without ventilation would create a harmful exposure.
The report also cites a 2025 study that found an increase in certain strains of airborne bacteria after scented candles were burned. That finding does not by itself establish that candle use causes illness. Croft said research on particulate matter more broadly links long-term inhalation with asthma attacks, worsening chronic obstructive pulmonary disease, cardiac events and other health effects; those broader findings do not establish the risk from typical candle use specifically.
How Candle Use Affects Indoor Air
For most readers, the report points to exposure and indoor ventilation as the practical issues, rather than showing that a scented candle is inherently dangerous. Candle emissions add to what is already in a room, and a small, poorly ventilated space with several candles burning for a long time may create a different exposure from occasional use in a larger, aired-out room.
People with asthma or allergies, and pregnant people, are advised by the experts to pay closer attention to potential air pollution and reduce exposure where possible. That is a precaution, not evidence in this report that ordinary candle use causes a specific health outcome in those groups.
The findings also matter because consumers cannot use a single candle count or burn-time rule to know when exposure becomes harmful. The evidence supports taking simple steps to limit smoke and improve airflow, while leaving the health risk from specific patterns of use uncertain.
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What Studies Have Measured
The report distinguishes between evidence about air pollutants in general and research on candles. Long-term exposure to particulate matter has been associated with respiratory and cardiovascular harms, but that does not show that emissions from a candle at household levels produce the same effects. The dose, duration and conditions of exposure matter.
A 2021 study discussed in the report measured ultrafine-particle emissions from five kinds of pillar candles over six hours. Croft said emissions appeared higher when candles first started burning and became relatively stable later. The paraffin candle had some of the higher readings in that example, but the candles’ emissions were in a relatively similar range. He said earlier research had raised concerns about paraffin, so avoiding it is a reasonable personal choice while evidence develops.
Good Housekeeping also cites a 2023 study by the Research Institute for Fragrance Materials. The source material does not provide enough detail about that study’s methods or findings to assess its scope independently. Nikaeta Sadekar, a senior scientist at the institute, said the research examined fragrance exposure from consumer products, including candles.
“In toxicology, the dose makes the poison.”
— Daniel Croft, associate professor at the University of Rochester Medical Center
The Exposure Threshold Is Unknown
Researchers have not established how many candles, for how long, or in what room conditions would produce a harmful exposure. Results from studies using simulated household conditions cannot settle the risk for every home, candle formulation or pattern of use.
The report describes a 2025 finding involving airborne bacteria, but the provided material does not specify the bacterial strains, the size or duration of the increase, or whether it led to health effects. It also does not provide enough information to judge the methods and conclusions of the cited 2023 fragrance study. Those gaps mean the findings should not be treated as proof that scented candles are either harmful or risk-free.
Practical Steps While Evidence Develops
The experts cited by Good Housekeeping recommend paying attention to airflow and personal symptoms. Opening a window or otherwise improving ventilation can help clear indoor pollutants. Limiting the number of candles burning at once and the time they remain lit can also reduce the amount released into a room. People with asthma or allergies, and pregnant people, can choose to avoid or reduce exposure if they have concerns.
There is no specific safe candle count or universal burn-time limit in the report. Further research would need to measure emissions and health effects across different candle types and real-world indoor conditions to clarify exposure levels. Until then, the evidence supports practical ventilation and moderation, not a blanket conclusion that scented candles are dangerous.
Key Questions
Are scented candles proven to be harmful?
No. The report says typical-use studies have mostly measured emissions below thresholds of concern, but researchers have not established a precise threshold that applies to every home or candle.
Do scented candles release pollutants?
Yes. Burning candles can release soot, particulate matter and volatile or semi-volatile compounds. How much enters the air depends on the candle and the conditions in the room.
Are paraffin candles riskier than other candles?
Some studies have found higher particle emissions from paraffin candles, but the 2021 comparison described in the report found emissions across five candle types in a relatively similar range. The evidence does not establish a clear risk ranking.
How can I reduce exposure when burning candles?
Improve ventilation, avoid burning many candles at once, and limit how long they burn. The report gives no universal safe number of candles or burn-time limit.
Who should take extra care?
The experts advise people with asthma or allergies, as well as pregnant people, to pay closer attention to potential indoor air pollution and reduce exposure where possible.
Source: goodhousekeeping.com
