The first study to map food allergies across the U.S. finds that children growing up in the suburbs are at greatly reduced risk of dangerous peanut and shellfish allergies.

Study of the DayKaren Sarraga/Shutterstock

PROBLEM: Every three minutes, a food-related allergic reaction sends an American to the emergency room. Since past research has shown that asthma, eczema, and conjunctivitis are more prevalent in urban areas than rural ones, are allergies more rampant in cities as well?

METHODOLOGY: To uncover the geographic distribution of childhood food allergies in the U.S., researchers led by Northwestern University's Ruchi S. Gupta conducted a nationally representative survey electronically from June 2009 to February 2010 to adults in U.S. households with at least one minor. They mapped information involving 38,465 children using their home zip code, and controlled for household income, race, ethnicity, gender, and age.

RESULTS: In urban areas, nearly 10 percent of children have food allergies, compared to just over six percent in rural communities. Peanut allergies are twice as common in urban centers, while shellfish allergies are more than twice as prevalent in urban centers. Still, regardless of where a child lives, food allergies are equally severe. Almost 40 percent of food-allergic kids in the survey had already experienced a life-threatening reaction.

CONCLUSION: Food allergies are much more rampant among children living in cities than those living in the suburbs.

IMPLICATION: Gupta says higher population density appears to be a risk factor for developing food allergies. "Similar trends have been seen for related conditions like asthma," she says in a statement. "The big question is -- what in the environment is triggering them? A better understanding of environmental factors will help us with prevention efforts."

SOURCE: The full study, "Geographic Variability of Childhood Food Allergy in the United States," is published in the journal Clinical Pediatrics.