Jun 19, 2014 1:00 PM

Author: Libby Mitchell


Every parent has had it happen. You turn your back for just a second and then turn around to find your baby or toddler touching something dirty or, worse yet, putting it in their mouth. The reaction is standard: you scream and grab the item, dispose of it, and then try to disinfect every place it may have touched your child. But is that really what you should do?

A theory that has floated around parenting communities for years is called the “hygiene hypothesis.” It states that keeping kids too clean in early life makes them susceptible to illness later in life by suppressing the natural development of the immune system. However, there has always something that didn’t quite make sense with this theory: kids in the inner city and rates of allergies and asthma among those kids. “The hygiene hypothesis would be great, “ says Cindy Gellner, MD, a pediatrician with University of Utah Health, “except that kids in inner cities, where they are more likely to be exposed to dirt, roach, and mouse allergens, are more likely to get sick, and have allergies and asthma.”

Researchers at Johns Hopkins Hospital say they now are able to explain this disconnect: it’s not just being exposed to germs and allergens that strengthen the immune system – it’s being exposed to the right kind at the right time.

Yep, you need to make sure your kid is interacting with the right kind of filth, at the right moment.

According to the study children exposed to cockroach, mouse and animal allergens, and those exposed to bacteria in the Bacteriodes and Firmicutes groups were less likely to suffer from allergies and asthma later if they were exposed in the first year of life.  Those exposed to more than two of the allergens/bacteria did the best of all. The researchers say it’s likely because there are “protective” qualities in these germs and allergens — and the protective effect is additive.

Parents shouldn’t go out and pick up pet mice and cockroaches for their new babies though. “This is still very new research,” says Gellner, “a lot more investigation needs to be done, and clinical trials need to be performed before we really know its value. Plus, a family history of allergies, asthma, and eczema may still override any protective effect of these allergens.””

So, for now, continue to keep the wet wipes handy. Just don’t be concerned if you don’t get every single spot of dirt.


Libby Mitchell

Libby Mitchell is the Social Media Coordinator for University of Utah Health Care. Follow her on Twitter @UUHCLibby

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