America may be the land of plenty, but according to a study published in the April 29 online JAMA Pediatrics, it is also the land of hay fever, asthma, food allergies and eczema.
Researchers, led by Jonathan I. Silverberg, MD, PhD, of Beth Israel Medical Center and St. Luke’s-Roosevelt Hospital Center in New York City, suggest that kids and teens living in the United States but born outside its borders have a lower prevalence of asthma and allergies than children born in the U.S.
According to a JAMA Pediatrics news release, the study analyzed data from the 2007-2008 National Survey of Children’s Health. Data included responses to a cross-sectional questionnaire related to 91,642 children from newborn to age 17 to determine allergy rates among children born in the U.S. and those born overseas.
Study results show that children who were U.S. citizens but born abroad were about half as likely to develop allergies or asthma as kids born in the U.S.
“The results of the study suggest that there are environmental factors in the U.S. that trigger allergic disease,” Silverberg told Reuters Health.
“Children born outside of the U.S. are likely not exposed to these factors early in life and are therefore less likely to develop allergic diseases,” added Silverberg.
In addition, study authors looked to the hygiene hypothesis, which suggests that children in the U.S. are too clean — that they are not exposed to common allergens and therefore do not build up an immunity to them.
“The findings of the present study are consistent with the broader hygiene hypothesis, which suggests that either infections or certain microbial exposures may confer protection against atopic disorders,” the researchers wrote.
However, when researchers compared allergies among foreign-born, U.S.-citizen children who lived in the U.S. for longer than a decade with foreign-born U.S.-citizen children who lived in the U.S. for two years or less, they found that the risk of allergies increased the more time foreign-born children spent in the U.S.
“This suggests,” they wrote, “that the protective effects of the hygiene hypothesis may not be life-long and that subsequent exposure to allergens and other environmental factors may trigger atopic disease later in life.”
Silverberg told Reuters Health that he hoped study results would lead to additional studies on what puts U.S. kids at risk for allergies and how to prevent them.