Children living in urban centers have a significantly higher prevalence of food allergies than those living in rural areas, US study data show.
The study found that children living in big cities are more than twice as likely to have peanut and shellfish allergies compared with those living in rural communities.
"We have found for the first time that higher population density corresponds with a greater likelihood of food allergies in children," said lead author Ruchi Gupta (Northwestern University Feinberg School of Medicine, Chicago, Illinois) in a press statement.
Gupta and team collected survey data on the prevalence of food allergies (peanut, shellfish, milk, fin fish, egg, tree nut, wheat, and soy) for 38,465 children under 18 years of age who were living in the USA during 2009 to 2010.
Geographic areas were classified as urban centers (most urbanized), metropolitan cities, urban outskirts, suburban areas, small towns, and rural areas (most rural) using Rural-Urban Commuting Area Codes.
Overall prevalence of food allergy increased significantly with increasing population density, from 6.2% in rural areas to 9.8% in urban centers, report the researchers in Clinical Pediatrics.
Prevalence rates for specific allergens also varied significantly by urban/rural status. Specifically, peanut allergies were twice as prevalent in urban centers as in rural areas (2.8 vs 1.3%), while shellfish allergies were more than twice as common in urban versus rural areas (2.4 vs 0.8%).
Only milk and soy allergy appeared to affect a similar proportion of children regardless of geographic area.
Allergies were significantly more common at southern and middle latitudes compared with northern latitudes, but after accounting for this along with race/ethnicity, gender, and age, living in an urban center was still associated with a greater probability of having a food allergy than was living in a rural area (odds ratio=1.7).
Of note, food allergies were equally severe regardless of where a child lived, and nearly 40% of food-allergic children in the study had already experienced a severe, life-threatening reaction to food.
Food allergy is a serious and growing health problem, affecting 8.0% of children in the USA. The prevalence rate has increased by at least 18% over the past decade.
The study data show that "environment has an impact on developing food allergies. Similar trends have been seen for related conditions like asthma," said Gupta.
"The big question is ‑ what in the environment is triggering them? A better understanding of environmental factors will help us with prevention efforts."
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