Mounting evidence suggests that the trillions of bacteria, fungi, and viruses that line our skin and digestive tracts—called the microbiome—may be key to a healthier immune system. In particular, being exposed to the right bacteria at an early age may reduce a child's asthma risk, says B. Brett Finlay Ph.D., a microbiologist at the University of British Columbia in Vancouver.

“Asthma is a very prevalent disease in our society now, which wasn’t the case 50 years ago,” Finlay says, who spoke on the topic at the recent meeting of the American Association for the Advancement of Science (AAAS). “We now realize that the microbes [you’re exposed to early in life] seem to set you up—or not—for asthma.”  

Although research in this field is still preliminary, evidence so far suggests that asthma risk may be greater in children who were born by C-section, fed formula instead of breast milk, or treated with antibiotics at an early age, as well as those who live in urban, rather than rural, areas. All of these factors, Finlay says, may limit a child’s exposure to healthy microbes.  

A Bug a Day May Keep The Inhaler Away

In 2012, Finlay and his team found that if you wipe out a young mouse’s intestinal bacteria with antibiotics, it's much more likely to develop asthma.

To see how the relationship between bacteria and asthma might play out in people, Finlay and his team compared the fecal bacterial content of 319 children enrolled in the Canadian Healthy Infant Longitudinal Development Study, a long-term research project examining the development of 3,500 children born after 2010. The team found that the infants who harbored four types of bacteria in their guts at 3 months of age were less likely to develop asthma than those who did not.

“If you had them [the bacteria], you were basically protected against asthma,” says Finlay. “If you didn’t have them, you had a very high risk of asthma.”

They published these results in the journal Science Translational Medicine in 2015.

This and other studies, says Finlay, hint that there might be an important early window when an infant needs to get certain microbes in order to strengthen their immune system and tip the balance away from developing asthma. "These microbes are somehow influencing how that actually works," says Finlay.  

Finlay believes that because we’re so focused on cleanliness, we’ve lost an essential part of our biology—healthy microbes. “We are suffering from a hygiene hangover,” says Finlay. “We are not getting the microbes that our grandparents got.” And as a result, he says, we’re getting diseases our society wouldn’t have seen 100 years ago. 

5 Ways to Strengthen Your Child's Microbiome

Once a child develops asthma, there's not much you can do to reverse it. That's why, says Finlay, it may be important to put certain practices into play early on in a child's life.

In his book, “Let Them Eat Dirt,” (Algonquin Books, 2016) Finlay outlines tips for increasing a child's exposure to healthy bacteria. Ideally, he says such exposures are most important between birth and age 2. But all of the tips can be practiced throughout childhood, which may help mitigate the risk of not only asthma, but other diseases linked to an unhealthy microbiome, including allergies, inflammatory bowel disease, and obesity. 

“It’s fascinating, and there’s a lot more to learn,” says Jay Portnoy, M.D., director of allergy, asthma, and immunology at Children’s Mercy Hospital in Kansas City.

He cautions, however, that the link between asthma risk and the microbiome is still not fully understood. A diverse microbiome, he says, may only be a marker for living in a healthy environment. “We don’t know whether changing the microbiome makes any difference for asthma,” Portnoy says.

And of course, asthma has many other triggers, including exposures to dust and pollen, and practicing these tips aren't a surefire way to spare your child.

Still, early research suggests they may help, and with basic precautions, all can be safely incorporated into a healthy lifestyle.

1. Let your child play in the dirt. Mud, plants, insects, and dirt are teeming with healthy microbes.

2. Get a dog. Assuming, of course, no one is allergic, studies show that people who live with a dog have a 20 percent decreased risk of developing asthma, says Finlay.

3. Chuck the antibacterial soap. Antimicrobial soaps and gels may seem like a smart idea, but they’ll destroy the beneficial microbes your child has picked up. Washing with regular soap and water is enough; and the only time your kid’s hands need to be squeaky clean, says Finlay, is before a meal and after the bathroom.

4. Feed their microbes. Like humans, microbes need to eat to stay healthy. And they prefer high-fiber, healthy foods like nuts, legumes, and vegetables, as well as fermented foods, like yogurt and kefir.

5. Use antibiotics sparingly. These drugs can be a lifesaver for serious infections, but when they’re not necessary—for colds or other viral infections, for example—skip them. They “carpet bomb” both good and bad bacteria, as Finlay says, dramatically disrupting the composition of microbes in your body.