Recent research has shown that the smoke from burning candles indoors, especially in poorly ventilated rooms, releases a mixture of chemicals linked to an increased risk of cancer.
Dangers of scented candles
As the use of scented candles expands, experts are raising new concerns about indoor air pollution from synthetic fragrances and paraffin wax.
Paraffin (also known as “mineral wax”) is the base material of most commercial candles. Because it is a byproduct of petroleum refining, it is cheap and efficiently transports flavor and color. However, when burned, it releases small amounts of volatile organic compounds (VOCs) such as benzene, toluene, and formaldehyde. These substances are known to cause respiratory irritation, and some are classified as carcinogens when exposed to large amounts.
Scented candles also release substances such as phthalates, which help extend the lifespan of scents and have been linked in some studies to hormonal disruption.
In addition, combustion produces hydrocarbons such as alkanes and alkenes, similar to those found in car exhaust.
Paraffin candles produce more soot than plant-based candles (such as soy or beeswax), especially if they have long wicks or burn irregularly. The effects are also more severe in poorly ventilated areas, where pollutants accumulate rather than spread.
In a recent article published on the website The Conversation, Karen Rosenkilde Laursen, a researcher at Aarhus University in Denmark, describes experiments conducted in a controlled exposure chamber that showed that particles resulting from burning candles are very small (about 7 to 8 nanometers), much smaller than those resulting from cooking (about 80 nanometers), and therefore can penetrate deep into the lungs and even into the bloodstream.
harmful gas
In addition to soot, candle smoke also contains harmful gases such as nitrogen dioxide and polycyclic aromatic hydrocarbons, which can lead to inflammation and cancer risk. This soot leaves dark marks on walls and surfaces and is similar in size and composition to PM2.5 particles from car exhaust, forest fires, and fuel combustion.
Signs and symptoms of infection
Experiments have shown biological changes such as airway irritation, increased inflammatory markers, decreased lung function, and cardiovascular effects, with the most vulnerable groups including asthmatics, children, the elderly, and people with chronic respiratory diseases.
PM2.5 is associated with an increased risk of Alzheimer’s disease, the most common form of dementia.
In a large study conducted by Emory University in Georgia and published in February 2026, researchers found that a small increase in PM2.5 exposure increased the risk of Alzheimer’s disease by about 8.5 to 9 percent, with a stronger effect (about 11 percent) in people who had previously had a stroke.
It is estimated that this will lead to an additional tens of thousands of cases of infection among elderly people.
Around 900,000 people are currently living with dementia in the UK, and that number is expected to rise to more than 1.6 million by 2040, with dementia being the leading cause of death (more than 74,000 people a year).
expert tips
To reduce the risk, experts advise reducing the use of candles, cutting the wicks regularly to reduce soot, avoiding burning in drafts, avoiding lighting candles near people with respiratory illnesses, and opening windows to ventilate the room after use.
The latest scientific research shows that the amounts emitted are often small and do not pose an immediate danger under normal use, but caution should be taken in chronic exposure, especially in the winter with windows closed.
