According to a new study published Monday, children and teenagers born in the United States are nearly twice as likely to have asthma and other allergies as those who are born abroad and immigrate to the U.S.
Reuters Health reports that parents of about 80,000 children were surveyed in the 2007-2008 National Survey of Children's Health. The findings show that not only have allergies of all kinds increased in recent years, but it is especially so in the United States.
"Food allergies have increased tremendously," Dr Ruchi Gupta of Northwestern University Feinberg School of Medicine in Chicago told Reuters Health. "We do see people who come from other countries don't tend to have it, but immigrants who are maybe second generation, they're identical (to U.S.-born people)."
Although it is not certain why this pattern holds true, researchers have a number of ideas. Gupta claims that it could be due to the poor quality of American diets or the hygiene hypothesis, which states that children in the U.S. are cleaner than in other countries, hindering their immune systems that never get exposed to common allergens.
Other hypotheses include climate, obesity, and other infections common in the U.S.
"The results of the study suggest that there are environmental factors in the U.S. that trigger allergic disease," reported lead researcher Dr. Jonathan Silverberg from Beth Israel Medical Center and St. Luke's-Roosevelt Hospital Center in New York Reuters Health in an email to Reuters Health. "Children born outside the U.S. are likely not exposed to these factors early in life and are therefore less likely to develop allergic diseases."
Approximately 20 percent of children not born in the U.S. had some kind of allergy, including asthma, eczema, hay fever, and food allergies. In comparison, between 34 and 35 percent of parents of children born in the U.S. reported allergic diseases in their kids.
Furthermore, foreign-born children who spend time in the U.S. also reported a higher risk of allergies according to Silverberg. According to U.S. News, it does not matter what age participants were when they moved to the U.S., but the allergic diseases start appear after about 10 years of living here. Therefore, just by moving to the U.S., residents have an increased risk of obtaining allergies.
"You acclimate to wherever you are and you pick up whatever is going on there," Gupta explained.
The study continues in an effort to learn what causes allergy risks in U.S. children and how to prevent them. A well-balanced diet is encouraged, as well as letting your children get dirty every once in awhile - making sure they wash their hands afterward.
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