Research published in the Guardain reports children whose outdoor play areas were transformed from gravel yards to mini-forests showed improved immune systems within a month.

Across the western world, rates of autoimmune diseases, where the body mistakenly attacks itself, are rising. The diseases include asthma, eczema, type 1 diabetes, inflammatory bowel disease and multiple sclerosis. A leading possible explanation for this trend, called the hygiene hypothesis, is that children are being exposed to far fewer microbes than in the past. This means their immune systems are less challenged and more prone to making mistakes.

The scientists believe this is because the children had developed significantly more diverse microbes on their skin and in their guts than the children whose playgrounds were not upgraded.

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