Young inner-city children may suffer disproportionately from food allergies, according to a recent study.

Researchers from Johns Hopkins Medicine found that at least one in 10 children from four large cities in the United States has a food allergy. However, the true number may be even higher because the study used highly stringent criteria and counted only the three most common food allergies, investigators explained.

Food allergies among children have been on a steady rise over the last 20 years, and experts have long suspected that children in urban areas are no exception. The new study largely affirms that trend but also points to a subgroup of children who may have higher-than-average allergy risk.

"Our findings are a wake-up call, signaling an urgent need to unravel the causes, contributors and mechanisms that drive the high prevalence of food allergies among an already vulnerable group known for its high risk of asthma and environmental allergies," said senior investigator Robert Wood, director of pediatric allergy and immunology at Johns Hopkins.

According to the latest estimates from the National Institutes of Health, nearly 3 percent of adults and 6 percent of young children in the United States have one or more food allergies.

For the study, researchers followed more than 500 inner-city children from birth through age 5 living in Baltimore, Boston, New York City and St. Louis. Each year of the study, the investigators measured each child's exposure to household allergens, conducted physical exams, tracked the children's diets and reviewed their health histories.

The team also analyzed blood samples at 1, 2, 3 and 5 years to measure the presence of food-specific immunoglobulin E (igE) antibodies to milk, eggs and peanuts.

Overall, 55 percent of children in the study were classified as sensitive to milk, eggs or peanuts. Nearly 10 percent of them met criteria for a full-blown food allergy. The most common allergy was to peanuts (6 percent), followed by eggs (4.3 percent) and milk (2.7 percent).

They also found that breastfed children appeared to have a higher risk for developing food allergies. Children living in houses with higher levels of endotoxin, a molecule released by certain types of bacteria, were less likely to have a food allergy.

Children with food allergies were also more likely to suffer from environmental allergies, wheezing and eczema, an allergic skin condition.

The findings were recently published in the Journal of Allergy and Clinical Immunology.