Is it healthier to use household cleaning products – or not?

Our use of cleaning products has increased significantly since Covid-19. But some of the products we're using to clean our homes come with their own health risks.

More recently, the Covid-19 pandemic has changed our everyday hygiene habits, with many people becoming more conscious of potential pathogens in the home.

Household cleaning products, including antibacterial spays, promise to kill most of the harmful bacteria in our toilets, on our kitchen surfaces and elsewhere around our homes.

What are the risks involved with cleaning our homes regularly – and should we be worried about the products we're using?

Using household cleaning products is one of the "modifiable risk factors" of asthma, says Emilie Pacheco Da Silva, postdoctoral researcher at Inserm, the French National Institute of Health and Medical Research, where she specialises in the asthma effects of disinfectants and cleaning products.

This means it's a behaviour that can be changed to lower the risk of developing the condition and experiencing symptoms.

The scientists found that regular use of cleaning sprays increases the risk of developing asthma, triggering current asthma, and poorly controlled asthma in adults, and wheezing in children.

"There's enough evidence to know that cleaning products are harmful to some people, particularly if they use them a lot. What's harder is which specific chemicals cause damage," says Nicola Carslaw, professor of indoor air chemistry at the University of York in the UK.

She expected the data to show that using household wipes containing disinfectant on a weekly basis would have a harmful effect on asthma, and the use of green and homemade sprays and wipes would be less harmful. She initially saw that weekly use of products in all three categories were associated with asthma.

However, when Pacheco Da Silva studied the weekly use of individual product categories while also taking into account people's weekly use of irritants or sprays, the association with asthma disappeared for products branded as "green" and homemade products, whereas the use of wipes remained significantly linked with asthma.

The study indicates that "the household use of green and homemade products could be less harmful to asthma, but that the use of wipes could be deleterious," says Pacheco Da Silva.

However, she says, there's no standard definition for "green" cleaning products, which may skew the study's findings. Indeed, it is a term commonly misused in marketing slogans (read Isabelle Gerretsen's story on why terms like "green" don't always mean what you think). Carslaw adds that "green" cleaning sprays aren't necessarily any better for us, though, because our bodies don't know the difference between natural and manmade ingredients.

"With a lemon-scented cleaning product, for example, it doesn't matter if the scent is lemon or factory-made, it's the same compound when it's released into the air," she says.

Some people choose to use homemade cleaning products on the assumption that they're healthier. But while there's some general ideas around what these ingredients can be – water, citric acid, salt, baking soda – there's no official recipe, and there's a lack of information around how active ingredients should safely be used, scientists say.

Some studies show that using certain antibacterial products can cause a cross reaction with certain antibiotics, which means you might get a resistance to those antibiotics, which hinders their effectiveness, says Elaine Larson, professor of epidemiology at the Columbia University Mailman School of Public Health in the US.

"Eventually we may theoretically reduce the ability of the immune function to respond to an encounter with organisms," Larson says.

Larson wanted to see if there was any health benefit when it came to using products labelled as antibacterial. She gave 238 families living in Manhattan products like a kitchen spray and hard-surface cleaner (either antibacterial, or that didn't contain antibacterial ingredients) at random – all commercially available, but with the labels removed. Larson then monitored the participants every week for almost a year and took note of any respiratory viral symptoms they reported (flus, colds, coughs and runny noses).

At the end of the study, Larson found no difference in respiratory symptoms between the two groups of participants. Ultimately, it didn't seem to matter whether their laundry, bathing and hard-surface cleaners contained antibacterial ingredients or not.

"This was pretty good evidence that the most important thing is the friction [between the surface and cloth, caused by the action of cleaning], and it doesn't matter so much whether a product [contains something] labelled anti-bacterial," she says. Other studies have found that showering and bathing with nonantibacterial soap increases how much skin bacteria is dispersed into the air around us – and Larson is suggesting a similar mechanism may happen when we clean our homes.

However, Larson concludes in the study that the types of infections most likely to be influenced by household cleaning, such as gastrointestinal disease, may be bacterial in origin – and the products selected in the study didn't claim to have anti-viral properties.

The reason for this, Larson says, is that antibacterial products don't always deter viruses, which can be airborne and are often the cause of respiratory infections.   "Things on the outside of our bodies are much less likely to cause contamination than breathing in the flu, so antibacterial products aren't affecting the transmission dynamic," she says.

However, Larson adds, antibacterial products may help with gastrointestinal or bacterial infections, like salmonella, by killing or inhibiting the growth of harmful bacteria. She writes in her paper, though, that any potential benefit of using antibacterial cleaning products must be weighed against a theoretical risk for antibiotic resistance. A University of Sheffield study found that "gentle" cleansers – those without antibacterial ingredients – can kill "enveloped" viruses (viruses with an outer layer) including coronavirus.

Scientists don't know the exact mechanisms behind the links between household cleaning products and our health, but the general advice is to minimise our exposure to them, Carslaw says, and only use them as often as we need to.

"No one would suggest you stop cleaning, because it's had a massive impact on reducing the amount of diseases we used to get 50 years ago," Carslaw says.

However, we should always ensure there's good ventilation in the room we're cleaning, such as an open window, Carslaw adds.

Another way to lower the risk to our health, she says, is to use liquid cleaners rather than sprays.

"Sprays are effective at converting chemicals in a product into aerosols, which are easier to breathe," she says. "With liquid products, you don't get the same dose."

Carslaw also advises cutting down on cleaners that have lots of added fragrances, as this generally increases the likelihood of them containing products that will irritate our airways.

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