Here's proof that being too clean is actually harming our kids

Muddy girlBill Pugliano/Getty ImagesA muddy girl, keeping her immune system strong.

We went overboard with the Purell.

Public health experts call it the hygiene hypothesis: While you might think cleaner is always better, research suggests that a little grit is good for you.

The hypothesis was coined by British epidemiologist David Strachan in 1989. He noticed kids in larger families were more likely to get hay fever, reasoning the more exposure to allergies the kids had, the greater tolerance they could build.

Since then, the hypothesis has provided an explanation for the rise in auto-immune disorders in developed countries, like type 1 diabetes, multiple sclerosis, inflammatory bowel diseases, and, most popularly, asthma and allergies, which have been on the uptick in the U.S. for years.

The researchers who study the hygiene hypothesis propose our over-sanitised, germ-free lives are to blame. We’ve replaced overtly nasty ailments like gout and ringworm, found in our poorly stored and undercooked food, with less obvious conditions that we carry for the long-haul.

Purell and hand washing may make hospitals safer, but those oh-so-helpful clinical rituals may backfire in everyday life.

Like with with raising kids, for instance.

Yale University immunologist Dr. Christina Price points to research done on farms to suggest a sort of prenatal protection from bacteria that sticks with kids later in life.

Mums, then, might do well to limit their sanitary practices.

“Encouraging kids to play outside is wonderful,” Price tells Business Insider. “But even that may be too late if you are already ‘sensitised.'”

Post-delivery, the benefits seem to compound the initial set of conditions.

A study published recently in the journal “Pediatrics” found families that washed their dishes by hand suffered fewer allergies than their dishwasher-using counterparts. The explanation? Dirt actually boosted immunity.

The practice has also found its way into the place where kids get the sickest: school.

One example is Gever Tulley’s radical approach to pedagogy, Brightworks.

The San Francisco-based school gets kids learning by doing. They take apart home appliances. They superglue their fingers together. And they also happen to play in the dirt, exposing their immune systems to the very things most of us try to eliminate.

Improving public health isn’t necessarily a goal of Brightworks, but it could easily be an unintended virtue. And for a generation whose idea of playtime comes built-in with screens of all sizes, just getting outside could end up reaping the greatest rewards.

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