Want to lower health care costs and improve child health? Get dirty. With more than half of all children now allergic to something, a recently published study asserts that children simply aren’t exposed to enough germs.

The hygiene hypothesis is informed by the farm effect, an observation that children living on traditional farms are not developing allergies at nearly the same rate. Amish children on Indiana farms interact daily with dirt, dust, germs, and large animals. They also consume raw, unpasteurized milk, while a breadth of their age group peers experience far less exposure to the great outdoors, have no large animal interaction and live in tightly constructed homes while drinking pasteurized milk.

Correlation or causation? The answer isn’t clear. But the observation does make sense, along the same lines that breastfeeding does more for child health than formula. Given the choice between years of doctor visits for allergy injections and a little time in the mud, it seems like getting a little time outside is worth a shot.