Allergy, asthma less frequent in foreign-born kids in U.S.

But protection from some immune conditions weakens after several years

By Nathan Seppa, 12:19 PM May 2, 2013

Spending the first few years of life someplace other than the United States seems to protect against allergy and asthma. An analysis finds that children who were born elsewhere and moved to the U.S. are less prone to these immune ailments than U.S.-born kids. But for some allergic complaints, the mysterious protection weakens after long exposure to an American lifestyle, researchers report April 29 in JAMA Pediatrics.

The beneficial effect has all the earmarks of the hygiene hypothesis, whi...

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