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Candles release particles and other compounds into indoor air, but experts cited in a Good Housekeeping report say studies simulating ordinary household use generally found emissions below levels of concern. Researchers have not established a precise threshold for harmful exposure, so room size, ventilation, burn time and individual health can matter.
A Good Housekeeping report on scented candles finds that candles release smoke, particulate matter and chemical compounds, but experts say studies that simulate normal household use have generally measured emissions below levels of concern. Researchers have not established how much candle exposure, in a room of a particular size and with a particular amount of ventilation, could cause harm, leaving people with asthma or allergies and other sensitive groups to take extra care.
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 of candle burning under conditions resembling ordinary household use have mostly found amounts below thresholds of concern, regardless of candle type. Some evidence suggests paraffin and fragranced candles can produce more concerning emissions, though the report says measured levels are not likely to be a major concern in typical use.
Daniel Croft, an associate professor of pulmonary and critical care medicine at the University of Rochester Medical Center, said the health effects of particulate matter are linked to exposure over time. Research on particulate pollution more broadly associates long-term inhalation with asthma attacks, worsening chronic obstructive pulmonary disease, cardiac events and other health problems. Those findings do not establish that ordinary candle use causes those outcomes. The dose and duration of exposure matter, Croft said, along with the number and size of candles and the room’s size.
The report also cites a 2025 study that found an increase in certain strains of airborne bacteria after scented candles were burned. That result does not, by itself, show that candle use causes illness. The article notes a 2021 study of emissions from five types of pillar candles over six hours; emissions appeared higher when candles first began burning and later became relatively stable. The report does not provide a definitive risk ranking for all candles or circumstances.
How Indoor Air Changes Exposure
The practical issue is indoor air exposure, not simply whether a candle is scented. Emissions can accumulate more in a small, poorly ventilated room or 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 allowing fresh air in can reduce the concentration of pollutants, although the report does not specify a ventilation rate that guarantees safety.
People with asthma or allergies may be more sensitive to airborne irritants. The experts also advise pregnant women to pay closer attention to potential air pollution exposures. This is a precaution, not evidence in the report that candle use has been shown to cause a particular pregnancy outcome. For most readers, the available evidence supports limiting excessive exposure and paying attention to symptoms rather than assuming that every candle is hazardous.
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What Candle Studies Have Measured
The evidence described in the report comes from several kinds of research, and the studies answer different questions. The 2021 emissions study measured particles from five pillar candles during a six-hour period. A separate 2021 study discussed in the report examined carbon dioxide from two candles, comparing the amount that would need to be cleared with carbon dioxide exhaled by one 176-pound person. That comparison illustrates emissions in a room; it is not a finding that candles create the same overall health risk as a person in the room.
The report also refers to a 2023 study by the Research Institute for Fragrance Materials. Nikaeta Sadekar, a senior scientist at the institute, told Good Housekeeping that its assessment of fragrance exposure from burning candles found no concern for harm from consumer exposure. That view is attributed to the institute and should be read alongside the wider limits of the evidence: candle type, use conditions and exposure levels vary, and the report does not establish a single safe or harmful dose.
“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
No Clear Harmful Dose Established
Researchers have not established how many candles, burned for how long, in a room of what size and with what ventilation would produce a harmful exposure. The report says studies of ordinary use have mostly found emissions below levels of concern, but that does not settle the risks of frequent use, unusually poor ventilation or higher-emission products. It also remains unclear how much the 2025 finding about airborne bacteria means for health; the reported increase does not establish infection or illness.
Evidence about paraffin and scented candles is not conclusive enough to give a universal ranking. Experts cited by Good Housekeeping differ in emphasis: Rebuli describes possible emissions and generally low levels in normal-use studies, while Sadekar reports no concern based on the fragrance institute’s exposure assessment. The available material does not resolve how risks vary for every fragrance, candle formulation or individual.
Practical Steps While Evidence Develops
For now, experts cited in the report recommend ventilating rooms while candles burn and avoiding prolonged or excessive use, especially in small spaces. People with asthma, allergies or particular concerns can reduce exposure by burning fewer candles or not using them, and should stop if they notice irritation or breathing symptoms. The report does not set a formal limit on burn time or number of candles.
Further research would need to clarify real-world exposure across candle types and room conditions, and whether measured emissions translate into measurable health effects. Until more specific thresholds are available, the experts’ guidance is to consider the room, airflow, duration and personal sensitivity rather than treating all candle use as either risk-free or proven harmful.
Key Questions
Are scented candles proven to be dangerous?
No. The report says studies simulating normal household use have mostly found candle emissions below levels of concern. It also says the evidence does not define a harmful exposure threshold for every room or pattern of use.
Do scented candles affect indoor air?
Yes. Burning candles can release particulate matter, soot and chemical compounds. How much a person breathes in depends on factors such as candle number, burn time, room size and ventilation.
Are paraffin candles worse than other candles?
Some research cited in the report suggests paraffin candles may produce more particles, but the findings do not establish a definitive ranking or prove that typical use causes harm. The report says emissions across candle types in one study were in a relatively similar range.
What can I do to reduce exposure?
Improve ventilation while candles burn, avoid burning many candles for long periods in a small room, and pay attention to irritation or breathing symptoms. People with asthma or allergies may choose to limit use.
What does the airborne bacteria finding show?
The report cites a 2025 study that found an increase in certain strains of bacteria in the air after scented candles were burned. That finding alone does not show that candles cause infection or illness; its health significance remains unclear.
Source: goodhousekeeping.com
