This article originally appeared in the San Francisco Chronicle on August 27, 2014.
Look out, city dwellers. Lots of research has already shown children living in urban areas have increased risk of asthma and environmental allergies. Now a new report suggests they have higher rates of food allergies, too.
Ten percent of inner-city residents ages 5 or younger in a Johns Hopkins University study were allergic to either peanuts, milk or eggs. If they had included other types of food allergies, the researchers said, the percentage would be even higher. By comparison, 6 percent of children under 5 nationwide as a whole have any sort of food allergy.
Dr. Robert Wood, director of pediatric allergy and immunology at Johns Hopkins and the paper’s senior investigator, said scientists don’t know why food allergies are more prevalent in inner cities, but many of the current theories are related to the “hygiene hypothesis.” It’s the idea that children who grow up in very clean environments can develop hypersensitive immune systems that make them prone to allergies.
Wood pointed to a European study that showed youths who grow up on farms around agriculture and animals have low rates of childhood asthma and allergies. His own previous research revealed urban infants are less likely to develop the conditions if their homes have pet or rodent dander or allergens from cockroaches. And early exposure to a byproduct of certain household bacteria correlated with lower occurrence of food allergies in Wood’s latest report, which was published in the Journal of Allergy and Clinical Immunology.
Wood says it’s too early for scientists to draw conclusions – or for inner-city parents to change anything about their homes – but the findings, he said, signal that more research is needed.