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Our sense of smell plays a vital role in our survival. Scents influence our behaviour in interesting ways, from stimulating our appetite to warning us away from something potentially dangerous.
But bad smells – like stinky cheese, unwashed feet, rotten eggs or old garbage – are hardly made more tolerable by knowing the evolutionary importance of our nose. When we catch a whiff of something foul at home or in the office, we just want the smell gone. This is when many of us might light up a scented candle.
Designed to fill a space with pleasant aromas, scented candles can definitely help mask some bad smells. Even in the absence of other obvious odours, they can provide a subtle background scent to our surroundings.
But is it possible that scented candles might actually be bad for you? To help us sniff out the truth, we chatted with Deakin’s Dr Aaron Schultz and Associate Professor Svetlana Stevanovic about the potential health impacts of scented candles.
We know that scented candles release a fragrance when they burn – but how do they actually work? According to Schultz, it all comes down to the chemical composition of the candle itself.
‘Scented candles contain a combination of synthetic (lab-created) and/or natural fragrances (e.g., essential oils) embedded in the wax,’ Schultz says. ‘When the candle is lit and the wax melts, these fragrances are released into the air as volatile organic compounds (VOCs), chemicals that evaporate at low temperatures.’
As Schultz explains, there are potentially more than 100 chemicals released when burning scented candles, depending on ‘fragrance formulation, wax type and burning conditions.’
‘These [chemicals] include terpenes such as limonene (lemon scent) and alpha-pinene and beta-pinene (pine scents), as well as solvents like ethanol and, in some cases, hazardous compounds such as formaldehyde, benzene, toluene and xylene,’ he says.
So, are scented candles bad for you? And if so, why?
According to Stevanovic, the potential negative effects of scented candles result from chemical reactions that occur once the candle starts burning.
‘When the fragrances are released into the air from a scented candle, they can react with ozone and other indoor oxidants to produce different airborne chemicals and pollutants that have the potential to be toxic including benzene, toluene, formaldehyde and acetaldehyde,’ Stevanovic says.
‘Scented candles also release other potentially harmful pollutants into the air including polycyclic aromatic hydrocarbons (PAHs) and particulate matter (PM). These combustion products are classified as toxic or hazardous by agencies such as the EPA.’
So far, this might sound like bad news for you scented candle lovers. But as Schultz explains, the safest way to address household odours is to tackle the source rather than covering up smells with fragrance.
‘Any product designed to release scent into the air will emit VOCs, which can react with indoor ozone to form secondary pollutants such as formaldehyde,’ he says. ‘There is no truly “safe” home fragrance option – only options with different risk profiles.’
If you do want to use scented candles indoors, though, Schultz has a few suggestions for how to reduce your exposure to VOCs:
It’s also important to consider who is in the room. Scented candles may pose a greater risk to pregnant women, children, the elderly and people with respiratory conditions. In these cases, it’s best to refrain from using scented candles altogether.
If scented candles are bad for you, are there any candles that are actually good for you? Not necessarily, but according to Aaron, unscented candles may be less harmful than scented varieties.
‘Scented candles have been shown to release a greater number and higher levels of potentially harmful pollutants compared to non-scented candles,’ he says.
As for which types of candles are safest, some wax materials can make candles less harmful to your health.
‘Candles made from natural wax sources (soy, beeswax and coconut) are suggested to be potentially safer than candles made from paraffin wax that is derived from petrochemicals,’ Schultz says.
‘Although there is no safe threshold for exposure to particulate matter (such as soot) and VOCs, burning soy, beeswax or other non-paraffin candles in moderation, along with proper ventilation and/or indoor air filtration, should be considered generally safe.’
If burning scented candles could be bad for you, are there any good alternatives for covering up those unpleasant household smells?
According to Stevanovic, the first step should be to improve indoor air quality, before adding other fragrances to the mix. Here are a few practical steps:
As for alternatives to scented candles, Stevanovic says the following are lower risk (although not risk-free) options that avoid combustion-related pollutants (but still emit VOCs):
So, if scented candles are bad for you, should you use these alternatives instead?
As Stevanovic says, these have lower risks than scented candles but ‘ultimately, removing air fresheners, fragrances and scented candles entirely will most effectively improve your indoor air quality and make your living space safer for your family, pets and visitors.’
Associate Professor,
Faculty of Science Engineering & Built Environment,
Deakin University
