Why scented candles can be harmful to your health

Why scented candles can be harmful to your health
Why scented candles can be harmful to your health

What do caramelized apples, a pine forest and clean laundry have in common? Not much, except that all three are depicted on the glass packaging of a scented candle. Now that autumn has arrived again, tea lights and dinner candles are selling like hot cakes. Hema and Blokker are full of them. But beware: that fragrant coziness comes at a price.

“Scent is only a fraction of what a scented candle emits,” says ENT doctor Marta Becker of health organization Clarity ENT, near Philadephia (USA). This is why scented candles have an odor.

Waste in the air

When burning a candle, incomplete combustion occurs: this happens when there is too little oxygen present for a fuel to fully react with it. Because the fuel is not completely split into molecules, waste products are created, such as carbon dioxide and small black soot particles. And they can be harmful to your health.

The way a flame burns can affect the chemical composition of the emitted particles, said Richard Corsi, dean at the College of Engineering at the University of California, Davis. For example, a flickering flame, or a flame that has just gone out, produces more soot – a mixture of carbon, volatile chemicals and tar-like substances. A flame that burns stably produces less of these waste products.

Allergic to a candle?

The holder in which you burn your candle can also contribute to air pollution, according to Hans Plugge, director at toxicology and risk assessment company Safer Chemical Analytics. The higher the edge extends above the wick, the more likely the candle will produce soot. The high holder gives the flame less oxygen, he explains.

And no matter how cozy: that delicious apple cinnamon or lavender lime scent can also have an effect on your lungs. Scented candles can release certain essential oils, including citronella, which can cause an allergic reaction to people who are sensitive to it. Whether a candle is made from ‘all-natural ingredients’ or not makes no difference. ‘These so-called natural extracts are often even more powerful allergens than synthetic fragrances,’ says Plugge. ‘The latter are often specially made to have anti-allergenic properties.’

Natural wax is also polluting

Despite many candle manufacturers claiming the opposite, all candles release both soot and volatile organic compounds (also called VOCs). Even if they are made from natural beeswax, soy or paraffin, candles cause some degree of indoor air pollution.

What you can do to minimize your chance of an allergic reaction? “Avoid candles that consist of anything other than wax and a wick,” says Plugge. ‘Any added ingredient will increase the chance of an allergic reaction.’ The health effects can range from hives to eczema and from migraines to asthma-like symptoms.

More research is needed to better identify the health risks associated with candles, says Plugge. ‘We know a lot about the health effects of tobacco smoke or incense, for example, but too little light has yet been shone on candles. Only time will tell what the precise health risks are.’


Merav Pront is a digital editor at National Geographic and also regularly writes for the magazine. During her studies in human geography, she learned to place local phenomena in an international context. As a freelance journalist, she looks for the small stories behind the big news. She writes for the VPRO and the National Holocaust Museum, among others.

The article is in Dutch

Tags: scented candles harmful health


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