If timing’s right, cats and roaches may be good for kids’ allergies

baby and cat

Exposure to mice, roaches and cats before a child’s first birthday may confer protection against asthma and allergies, a new study suggests.


As I can attest, parents of newborns can get a little hyper about germs. Looking back, I’m slightly embarrassed by the amount of hand sanitizer that lived in our house when we first brought Baby V home. (But only slightly embarrassed. Newborns really don’t need your well-wishing neighbor’s phlegmy rattle.)

Sometimes, though, germs and other unsavory allergens can actually keep your baby healthier.

Urban babies exposed to cockroaches, mice and cats before their first birthday were less likely at age 3 to suffer from recurrent wheezing, a warning sign for asthma, than children who weren’t exposed to the allergens, researchers report June 6 in the Journal of Allergy and Clinical Immunology. (Bad news for dog-lovers: Pooch exposure didn’t seem to help.)

The results fit right into the hygiene hypothesis — the idea that a less sanitized lifestyle is actually good for kids. Farm kids who grow up wrangling animals, kicking up dirt and hiding in hay bale forts are less likely to have allergies and asthma, scientists have found.

But what about city kids, who are exposed to less bucolic dirt? For the new study, scientists studied 467 newborns in Baltimore, Boston, New York City and Saint Louis. In addition to looking for signs of allergies in the children, the researchers visited 104 homes and collected dust from living rooms and children’s bedrooms, looking for proteins from cockroaches, dogs, cats, dust mites and mice.   

Overall, about a third of the urban children suffered from recurrent wheezing at age 3. But when researchers parsed the data collected for the new study, a surprising trend appeared: Children exposed to mouse, cat and roach allergens during their first year of life were actually less likely to wheeze at age 3 than children who lived in more sterile homes. Scientists found a similar result for overall bacterial richness: The more diverse the bacteria in a home, the lower the risk of future asthma and allergies for a kid.

Putting aside the shock factor of cockroaches being good for you, the results point out the importance of timing for the allergen exposure. To reap the roach benefits, kids’ immune systems had to encounter these particular allergens during their first year. When the researchers looked at kids exposed to this inner city milieu in the second and third year, there was no reduction in wheezing at age 3.

The first few months might be the critical window for teaching the immune system the difference between good guys and bad guys, the researchers write.

Maybe that news will prompt some over-zealous parents to ease up on the dusting a bit in their child’s first year. Learning about the hygiene hypothesis has given me a little peace of mind. When I see Baby V with a mouthful of dirt, I’m not all that horrified. That dirt might actually be good for her.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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