The co-author of the new book Let Them Eat Dirt: Saving Your Child from an Oversanitized World is quick to point out that he's not suggesting parents let their kids chow down on, well, dirt.
But University of British Columbia microbiologist Brett Finlay, writing with colleague Marie-Claire Arrieta, is making the case for parents to ease up on their war against bacteria because early exposure can kick-start young immune systems to begin the war on disease.
That means holding off on hand washing and hand sanitizer, letting kids play more with their pets, feeding babies breast milk instead of formula, among other measures, to let kids get a mix of good and bad bacteria.
"We're not saying, 'Feed them dirt,' but let them be kids," Dr. Finlay said in an interview on Thursday. "You don't have to wash them off every time they're dirty, and wash them off before dinner. They don't have to be scrubbed clean."
Rather kids need to be exposed to bacteria because they have a profound role in how the body develops. For example, Dr. Finlay's own research with Dr. Arrieta has shown children who are introduced early on to some microbes can ward off asthma when they're older.
"Playing in a sandbox is okay," Dr. Finlay said, adding that parents need to operate within some reason. "You don't want them licking the floor of a major subway station."
But immune systems need to be built up for a life's work. "I'd jokingly say, 'We have an immune system. It's good to use it or we'll lose it,'" he added.
Infections were once a major cause of human illness, leading to a necessary tide of vaccines, clean water and antibiotics, said Dr. Finlay. All good, but things may have gone too far.
"What we're now realizing in our quest to get so clean is we're depriving ourselves of harmless microbes we have actually co-evolved with, that we would normally experience in normal childhood," he said.
Let Them Eat Dirt, which is to be published Sept. 10, is a mix of original research and a look at current science.
"We need a societal rethink of how we live with our microbes, pretty much through all of our lives, and this whole cleanliness is godliness approach has served a fabulous purpose as our society has developed, but I think now we need to rethink that a bit. It's okay to be a little bit dirty," Dr. Finlay said.
Asked about his own childhood exposure to dirt, he said he grew up on an Edmonton acreage and was robustly exposed to dirt. "We lived naturally in that sense," he said.
He and his wife, a pediatrician, raised their own two children by similarly exposing them to the world.
Dr. Finlay, who specializes in infectious diseases, said Dr. Arrieta came up with the idea for the book and talked him into working on it. "Initially I was a little bit worried because a book is an awful lot of writing," he said.
But the 57-year-old scientist said the turnabout came during a sabbatical in Glasgow. Dr. Finlay wrote a chapter and was inspired to carry on. That was about two years ago.
The pair wrote alternating chapters. "People who don't know any different can't tell who wrote each chapter," he said, a point of pride.
Now, Dr. Finlay said he is working on his second book, which is about bacteria and aging.
But first, there's Let Them Eat Dirt. Promoting the book means an authors' tour with varied North American stops and a visit to Britain. Dr. Finlay is looking forward to taking the book's message on the road.
"We think there's something here. If you care about kids, it comes into play," he said.