Yes, it’s important to wash your hands. It’s critical during cold and flu season and especially if you visit someone at the hospital.

The problem is — in the West at least — parents have taken the business of keeping clean way too far.

New science shows that blasting away tiny organisms called microbes with our hand sanitizers, antibacterial soaps and liberal doses of antibiotics is having a profoundly negative impact on our kids’ immune systems, says microbiologist Marie-Claire Arrieta, co-author of a new book called Let Them Eat Dirt: Saving Our Children from an Oversanitized World.

The assistant professor at the University of Calgary, along with her co-author, esteemed microbiologist Brett Finlay, make the case that we’re raising our kids in a cleaner, more hyper-hygienic environment than ever before. They say that overdoing it the way we are is contributing to a host of chronic conditions ranging from allergies to obesity. I chatted with Arrieta recently to find out more.

What inspired you and Finlay to write Let Them Eat Dirt?

We’re both microbiologists and we’ve been studying the community of microbes that live in our guts — what we call our gut microbiome. In recent years research from our lab and other labs has shown that the health of this microbiome early in life is really crucial to our lifelong health. It’s not just that we’re scientists but we’re both parents. We thought that parents and caregivers would really benefit from us bringing this knowledge to the public.

We’ve been hearing for some time that overusing antibiotics may lead to antibiotic-resistant hospital infections, something we may associate with the elderly and other immune-compromised people. But I gather the implications are much more immediate and individual than that. What’s the connection between microbes and the development of the immune system in childhood?

When we’re born we do not have any microbes. Our immune system is underdeveloped. But as soon as microbes come into the picture, they kick-start our immune system to work properly. Without microbes our immune system can’t fight infections well.

It’s not just the presence of these microbes but what they produce. They produce molecules and substances that directly interact with the cells of the lining in our guts, but also with the immune cells that are on the other side of the lining in our guts. They literally train them. It is only upon the encounter with these microbial substances that an immune cell obtains the information to do what they’re supposed to do. Then these cells in our gut have the ability to transport themselves to other parts of the body to do more training.

It was rare when we were growing up to learn of a peer having a severe nut allergy. In the book you touch on a theory known as the “hygiene hypothesis.” What is that?

The hygiene hypothesis tries to explain why allergies, as well as obesity and inflammatory bowel disease and even autism, these are all diseases on the rise. And this is not explained by genes alone. Our genes simply do not change that fast. Research is consistently showing that it’s these changes in early life exposure to microbes that are driving the rise of these diseases. The lack of microbial exposure early in life that is necessary for our immune systems to be trained properly and to eventually be able to avoid the development of these diseases.

Are there things parents can do — and not do — to make sure they develop a good healthy microbiome and perhaps lower the chances of children contracting allergies, asthma and other related conditions?

Epidemiological evidence shows that kids who are growing up on a farm environment have way less chance of developing asthma. Of course you cannot just pick up your things and become a farmer, but what this suggests is that living in an environment that is less clean is actually better. The same is true for owning a pet, specifically a dog. Let your baby safely play with dogs.

Studies have also shown that cleaning everything that goes in baby’s mouth increases their chances of asthma. The incidence of developing asthma is decreased if the pacifier is cleaned in the parent’s mouth. And all of this points to the fact that we are just living too clean, to a point that it is not beneficial. Hygiene is crucial to our health. We should not stop washing our hands, but we should do it at a time when it is effective at preventing disease spread — before we eat and after using the restroom. Any other time it is not necessary. So if your child is out in the backyard playing with dirt, you do not need to remove that dirt. There’s no benefit from doing so. There has to be a balance between preventing infection, which is still a real threat in society, but also promoting this microbial exposure that is healthy.

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Brandie Weikle is a parenting expert, the host of The New Family Podcast and editor of thenewfamily.com