What Forest Floor Playgrounds Teach Us about Kids and Germs

“There is this ‘biodiversity hypothesis,’ that in the absence of diverse environmental microbiota, people are more likely to get immune-mediated diseases,” says Aki Sinkkonen, an evolutionary ecologist at the Natural Resources Institute Finland. “The immune system doesn’t recognize microbes by species, but by their type,” says Sinkkonen. Not surprising: Previous studies have shown this subgenre to be associated more often with children who grow up on farms than city kids.The blood tests showed that kids who had played on the imported forest floor had also developed a higher ratio of inflammation-dampening molecules to pro-inflammatory ones. Sinkkonen says this is a signal that the kids’ immune systems were engaging with all the new bugs they were encountering. The skin and blood samples from the forest playground group looked much more like the positive control group, who played at daycares in the woods.These results suggest it might be possible to dial childrens’ immune systems to a well-balanced state simply by greening up the environments around them, says Sinkkonen. “I am really excited to see this study replicated at a larger level, and ideally with long-term follow-up to examine the influence on chronic immune health outcomes,” he wrote.Sinkkonen’s team did follow the playground cohort for two years, to see if the kids that played in the green spaces had lower rates—or less severe forms—of allergies, asthma, and other immune-mediated diseases.