How Being Outdoors May Help Kids’ Immune Systems

I love collecting stories and studies that prove what already feels true about kids and nature. This is one of those studies. Children plus nature feels like a good combination. Kids seem happier and more vigorous outside, don’t they? 

I often think of this quote from Frances Hodgson Burnett’s The Secret Garden

 . . . But the big breaths of rough fresh air blown over the heather filled her lungs with something which was good for her whole thin body and whipped some red color into her cheeks and brightened her dull eyes . . .

Whenever I find a study or an article that uses data to prove the benefits of spending time outside, I tuck it away in a self-satisfied portion of my brain. It’s just more of what we know in our souls to be true. Of course, I fully acknowledge that there are infinite situations where being outside is not the best thing for a child’s health. (Air pollution is just one thing to consider). For now, I’m talking about simply spending time safely in nature. The study I’ll discuss today is more information that nature is good for kids’ health. With a twist. 

The Human Microbiome and Our Immune Systems

In fact, it also involves another perpetually interesting topic: the human microbiome. Newer research refers to it frequently. It’s all that lives and thrives in and on our bodies. Bacteria. Viruses. Fungi. Evidence shows that it’s related to our immune system. Very generally speaking, the more diverse our microbiome, the better it is for our immune systems. 

I should note that when we talk about the immune system, it’s beyond just fighting infections. We must also think about autoimmune diseases like type 1 diabetes.

Delving more into the human microbiome may also be another topic for another day. Today, I’ll focus on this study. 

Add A Forest Floor for Better Health

The research showed that when kids were exposed to more greenery and a forest floor for 28 days, their microbiomes became more diverse! Their immune systems improved.

They studied kids at daycares in Finland. One group went to an actual forest regularly. Another had their usual urban playground. And with a third group? They brought sod and plants to their daycare for kids to play in and around. They literally covered the existing gravel with a “forest floor.” The results showed more diverse microbiomes of the gut and skin in the kids exposed to the green nature. The results in kids that visited the actual forest and those with the transported forest were comparable.

Also, no pathogens or harmful bacteria were found on the kids as a result of the intervention. 

Study Limitations

Of course, there are limits to this study. First, data was collected in 2016, so I can’t help but wonder about hand washing routines then compared to now in 2020. Would that affect the skin microbiome results?

Second, it was a small group of kids, just 75, so not enough to draw large overarching conclusions. It’s enough, in my opinion, to show this is a topic worth studying.

Third, it does not directly show that the nature exposure absolutely caused the changes in the microbiome. Causation versus correlation, right? There are many variables, and the paper acknowledges the challenges and limits of studying real kids who attend daycare and then go home to their likely variable lives. Pets. Siblings. Backyards. Home diets. Etc!

Also, this was Finland. In the paper, there was no comment on ethnic diversity of the children. They did discuss the plants used, and we have to consider different plants in different places. Moss and blueberries worked well for them, but would hardly be a practical choice in Arizona. Would the same results come from a child digging in desert sand or trying to climb palo verde trees?

Let’s Still Go Outdoors

Despite these limits, I love this study. First, the notion of just bringing dirt and plants to the daycares? It seems a bit fanciful. And yet? They did it. Like a child trying to bring a woodsy fairyland inside their home. 

Second, they showed that no harm was done. 

Third, the twinkling of a possibility that simply digging around in mud is good for the immune system is just incredibly life-affirming. 

Or maybe I just needed another reason to let my kids get dirty when we’re outside. Time with children outside is easier (and more fun) for me when I don’t worry about cleanliness. 

In the meantime, let’s keep an eye on this research topic. Also in the meantime? Let’s keep playing outside with our children. 


Rosland, Marja. “Biodiversity intervention enhances immune regulation and health-associated commensal microbiota among daycare children.” Science Advances, vol. 6, no. 42, 2020,

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