More and more people seem to be getting pollen, peanut and penicillin allergies. One theory suggests this may be the result of overprotective child-rearing.

(Conradcress/ThinkStock)

As one medical expert put it, "we do not allow our kids to roll around in the dirt enough."

"In our zeal to protect against harmful infections, we have inadvertently shielded ourselves and our children from the typical exposure to a diverse array of microbial life that had characterized all prior generations," says Bill Miller, author of "The Microcosm Within: Evolution and Extinction in the Hologenome."

Allergy expert Leonard Bielory, the director of the Allergy and Asthma Research Center in Springfield, agrees that too many kids are being shielded from minor allergens and toxins.

"The early environment that we put our children into, the more sterile it is, the more likely that you will have allergies downstream," he said.

There are now double the number of things that we are allergic to. Not only are there twice as many people with allergies now as there were 25 years ago, Bielory said, but "there are now double the number of things that we are allergic to." And that includes a heightened sensitivity to pollen that spawns allergies and asthma.

Bielory pointed to a study of twins in Europe who grew up separated. One twin went to live in the city, and one went to live on a farm. Those who lived on the farm had less allergies as they grew up. And the ones that lived in the city developed more asthma and allergies and associated conditions. That led others to believe that perhaps the environment that children are exposed to at an early age can help resist allergic reactions.

But Bielory adds it is not the only factor.

"If you do not have the genetic predisposition to have allergies, you are not going to have allergies," he said. But if one parent has allergies, there's a 30 to 40 percent chance the child. If both parents have allergies, there's an 80 percent chance the child will, too.

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