Allergy season can be brutal depending on where in the United States you live, because of pollution, pollen counts and other factors.
A new study suggests simply being born in America may be another reason to blame for allergies.
A study of a nationally representative sample of children finds that kids born outside the U.S. are significantly less likely to have allergic diseases like asthma, eczema, hay fever and food allergies than children who were born in this country.
However, people born outside the U.S. are not in the clear if they decide to reside stateside, the study also found.
"Foreign-born Americans have significantly lower risk of allergic disease than U.S.-born Americans," wrote the authors of the new study, published April 25 in JAMA Pediatrics. "However, foreign-born Americans develop increased risk for allergic disease with prolonged residence in the United States."
For the study, researchers at St. Luke's-Roosevelt Hospital Center in New York City examined data from the National Survey of Children's Health, a long-running U.S. study group of more than 91,600 kids between the ages of 0 and 16 who have been tracked since 2007-2008.
The researchers found 20.3 percent of children born outside the U.S. had one allergic disease, compared to 34.5 percent of those born in the States.
Race and ethnicity had no affect on these rates.
What's more, children born outside the U.S. had significantly lower odds of these problems if their parents were also born outside the United States, as compared to those whose parents were born in the States.
Children born outside the U.S. but lived in the country for longer than 10 years had significantly higher odds of developing any allergic disorders, including eczema and hay fever -- but not asthma or food allergies -- when compared to those who resided in the U.S. for only 0 to 2 years.
Is something in America's environment triggering allergies?
Yes, suspects study author Dr. Jonathan Silverberg, a researcher at Beth Israel Medical Center and St. Luke's-Roosevelt Hospital Center in New York City. While the study did not look specifically at environmental triggers, he told Reuters that climate, obesity and various infections may also be playing a role.
"The results of the study suggest that there are environmental factors in the U.S. that trigger allergic disease," Silverberg told Reuters. "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."
Experts not involved with the study noted they have seen similar patterns in their allergist practices.
Dr. Ruchi Gupta, a food allergy researcher and associate professor of pediatrics at the Northwestern University Feinberg School of Medicine in Chicago, told Reuters the findings may reflect the poor quality of American diets, or the "hygiene hypothesis" -- a theory that U.S. children are not exposed to enough germs and allergens early on, hindering the development of their immune systems.
Indeed, diet has been tied to allergies risk in recent research.
A January 2013 study in th} found children and teens who eat fast food at least three times per week were much more likely to have asthma, eczema and hay fever compared to healthier eating classmates.
In the United States, food allergy affects an estimated 5 percent of children under the age of 5 and an estimated 4 percent of people aged 5 and older, according to the National Institute of Allergy and Infectious Diseases.
Asthma affects more than 16 million adults and nearly 7 million children in the United States alone, the Institute added. Worldwide, 300 million people have the disease that attacks the lungs, causing wheezing, breathlessness, chest tightness, and coughing.
People with allergic rhinitis -- known as hay fever -- may experience symptoms in their nose when they breathe in something they're allergic to like plant pollen, grasses, ragweed, pet dander and dust mites. Nearly 17 million Americans -- or 7.3 percent of the country -- have hay fever, according to the Centers for Disease Control and Prevention.
Previous studies have found this effect in other countries, showing immigrants in Italy, Israel and Australia were less likely to have allergies than natives, Agence France-Press reported.
"It's not that living in the U.S. is bad," Dr. Punita Ponda, a physician in the division of pediatric allergy and immunology at Cohen Children's Medical Center of New York, told the AFP. "Living in developed countries is probably thought of as a risk factor compared to living in developing countries," explained Ponda, who was not involved in the study.