U.S. children born outside the United States have lower risk of allergic disease

The cross-sectional questionnaire used for the study was distributed to 91,642 children aged 0 to 17 years enrolled in the 2007-2008 National Survey of Children's Health. The main outcomes measured were prevalence of allergic disease, including asthma, eczema, hay fever, and food allergies.

According to the study results, children born outside the United States had significantly lower odds of any atopic disorders than those born in the United States, including ever-asthma, current-asthma, eczema, hay fever, and food allergies. Children born outside of the United States whose parents were also born outside the United States had significantly lower odds of any atopic disorders than those whose parents were born in the United States. Children born outside the United States who lived in the United States for longer than 10 years when compared with those who resided for only 0 to 2 years had significantly higher odds of developing any allergic disorders, including eczema and hay fever, but not asthma or food allergies.

"In conclusion, foreign-born Americans have significantly lower risk of allergic disease than US-born Americans. However, foreign-born Americans develop increased risk for allergic disease with prolonged residence in the United States," the study concludes.