Authors of ‘Let Them Eat Dirt’ Say Shielding Kids From Dirt May Not Make Them Healthier

“A dog will come and lick you and your kids. That's good,” an author said.

ByABC News
September 22, 2016, 8:13 AM

— -- The authors of the new book “Let Them Eat Dirt: Saving Your Child from an Oversanitized World" say keeping children too clean shields them from certain microbes that are essential for a healthy immune system, so children should be allowed to get dirty when they play.

The book's authors -- B. Brett Finlay and Marie-Claire Arrieta -- draw upon evidence that suggests allowing children to get dirty exposes them to healthy germs that can actually be good for them.

“If we miss out on that exposure, the immune system is not going to mature,” Arrieta, an expert in microbes and immunology, said in an interview with ABC News.

Failure to develop the immune system puts children at higher risk for asthma, diabetes and even obesity, the authors said.

Finlay and Arrieta say one of the best ways for children to get those essential microbes is for them to play in dirt. Children – especially those who are under 5 years old – should be allowed to play outside and get dirty, but within limits, they added.

“We do have to think a bit: let the kid lick the floor in your own house but not the subway station,” Finlay, a microbiology professor at the University of British Columbia in Canada, said.

The authors also say it’s okay that parents allow other people to touch their newborns, and it’s also okay to let the family dog lick the baby.

“A dog will come and lick you and your kids. That's good,” Arrieta said. “They are basically bringing in the outdoors into your home.”

The authors also say children don’t have to wash their hands after being outside and that parents shouldn’t panic if their baby’s pacifier falls on the floor.

“Put it in your own mouth ... don't wash it. Studies show that's beneficial in reducing asthma and obesity" in children, Finlay said.

This is a little much for Melissa Willets, a self-described germophobe who has three daughters.

“I worry about what they touch and then put their hands in their mouth or their eyes,” she said of her children, who are eight, five and three years old.

Willets chronicled her germ fears for a blog on

“You don't want to put your kids in a bubble. That's not healthy for them either. But it's hard not to want to protect them from germs,” she said.