Young children who grow up in households where their parents frequently use cleaning products are more likely to develop asthma by the age of three years old, a new study has found.

The study, which examined a group of 2,022 Canadian children aged between three and four months, found that the household products resulted in a higher risk of asthma and childhood wheeze by age three, though not atopy — a condition associated with heightened immune responses to certain allergens.

We’re conditioned to think that scents in the home are a sign of cleanliness, said lead study author Jaclyn Parks, a health sciences graduate student at Simon Fraser University.

“You go into someone’s home, you smell a nice cleaner smell, you’re like, ‘Oh wow, what a nice house.’ But really what you’re smelling is just pollutants in the air,” she said.

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For the study, published Tuesday in the Canadian Medical Association Journal, researchers gave parents a questionnaire asking them which kinds of products they used and how often.

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Scented spray products, like air fresheners and other aerosols, seemed to be associated with more issues, the study found.

“The actual art of spraying a chemical into your air means that it’s easier to inhale, so you’re having more of that exposure to the lungs,” Parks said.

“It also means that it can settle on dust and other surfaces, so when you go to clean the next day or a week later, you stir up these things from a cleaning event that happened a week ago. And then you’re getting exposed again.”

0:27 Asthmatic children aren’t using inhalers properly Asthmatic children aren’t using inhalers properly

The researchers aren’t sure why household chemicals seem to have this effect, though Parks theorizes that they either disrupt a child’s microbiome — the mix of bacteria in their bodies — or actually damage their lungs, making the child more susceptible to infection and allergy triggers later in life.

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The first year of a child’s life is critical, she said.

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“In that first year, they’re still developing their immune system, they’re still developing their respiratory system, and other developmental trajectories for disease health.”

“Asthma is increasingly understood to develop early in life and progress over time, with only a small window in early childhood during which preventive efforts may be beneficial,” wrote Dr. Elissa Abrams, an allergy specialist and assistant professor in the Department of Pediatrics and Child Health at the University of Manitoba, in a linked editorial in the CMAJ.

She noted that manufacturers of household cleaning products are not required to list all ingredients, and that claims that a product is “green” or “environmentally friendly” are largely unregulated.

Parks doesn’t recommend that people stop cleaning their homes, but rather that they think about cleaning them differently.

“The spray one is the bigger one, so things like those plug-in air fresheners, unplug them. Stop using them. Really you’re just covering up things in the home that you could be getting rid of,” she said.

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Rather than using spray products, she suggests applying liquid cleaners by using a cloth instead.

“Other things people can do is increase ventilation after cleaning events, so whether it means opening windows, maybe you have an air filter you throw on for an hour or so after you’ve been cleaning,” she said.

“And then just when you’re shopping, look at the ingredients. Use chemical products that have less ingredients in them and that might reduce your exposure.”

The American Lung Association recommends using only cleaning products that don’t have volatile organic compounds, fragrances, irritants or flammable ingredients, and that air fresheners should be avoided altogether, Abrams wrote.

More research is needed to see whether specific combinations of products are more harmful, or whether “green” products are that much better, Parks said.

But based on previous studies on air freshener sprays in the home, “Removal of scented products from the homes of families of children at risk of asthma, or with current asthma symptoms, is likely wise,” Abrams wrote.

Parks agrees.

“The smell of a clean home is no smell at all, is what I say.”

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– with files from Su-Ling Goh, Global News