Parents who obsessively clean homes to protect babies might want to relax a bit!

New parents who obsessively clean their homes to protect babies from germs might want to relax a bit, suggests a new study linking high exposure to cleaning products with an increased risk of childhood asthma.

Researchers surveyed parents about how often they used 26 common household cleaners over babies’ first three to four months of life. By the time the kids were 3 years old, children with the highest exposure to cleaning products were 37% more likely to have been diagnosed with asthma than those with the least exposure.

With greater exposure to cleaning products, kids were also 35% more likely to have chronic wheezing and 49% more likely to have chronic allergies, the study found.

“Parents are striving to maintain a healthy home for their children,” said study coauthor Dr. Tim Takaro of Simon Fraser University in Vancouver, Canada.

“We want parents to question the socially accepted norm that a home needs to smell like chemical-based cleaning products in order to be clean,” Takaro by email. “Instead, we propose that the smell of a healthy home is no smell at all.”

In other words, parents should read labels and look for items that are free of dye and perfume, and consider natural cleaning products instead of chemical alternatives.

The first months of life are critical for development of the immune and respiratory systems, and exposure to chemicals inside the home is particularly problematic because infants spend so much time indoors, the study team writes in the journal CMAJ.

Chemicals in cleaning products can cause chronic inflammation that may contribute to development of asthma or make symptoms more frequent or severe, the researchers note.

Most kids in the study were white, and most parents were non-smokers without any history of asthma.

Because asthma can be difficult to diagnose with breathing tests in very young children, researchers also tested kids’ skin for allergies and asked parents how often children experienced symptoms like wheezing.

The most commonly used cleaning products in the study were dishwashing soap, dishwasher detergent, multipurpose spray cleaners, glass cleaners and laundry soap.

The study wasn’t designed to prove whether or how any specific cleaning products or chemicals in these products might directly cause asthma symptoms.

The American Lung Association recommends against using cleaning products that contain volatile organic compounds, fragrance and other irritants, but manufacturers in Canada and the United States are not required to list all ingredients in cleaning products. Some “green” products may contain harmful substances, as these products are not regulated, the study team notes.

“While much remains unknown, we think that these cleaning products (and the chemicals they contain) act as irritants to the airways of growing children,” Dr. Elissa Abrams of the University of Manitoba, in Winnipeg, Canada, who wrote a commentary accompanying the study.

Young children who spend a lot of time indoors, and especially babies and toddlers who touch everything with their hands and mouths, may be especially vulnerable, Abrams said by email.

“The take-home message is that parents should be careful which cleaning products they use in the home,” Abrams said.