City living may have a causal effect on food allergy

Researchers from the John Hopkins Children’s Centre in the USA have found that at least 10% of children in four large US cities had a food allergy, compared with the national average of six percent. These findings support those of the 2012 Australian study that found metropolitan children are more likely to suffer food allergies than children living in regional areas. The ‘Growing Up In Australia’ study found almost 5% of six to seven-year-olds in city areas had a food allergy, compared to 3% of children living outside metropolitan areas.

In the current USA study, pregnant mothers were recruited to the study from inner-city Baltimore, Boston, New York City and St Louis between 2005 and 2007. Ultimately, 516 children participated in the study from birth for five years. Each year during the study, the researchers looked at the child’s health history, diet and exposure to household allergens. They also took blood samples to measure the presence of immunoglobulin E (IgE) antibodies to the three most common food allergies: peanuts; eggs; and milk. While 55% of children in the study were found to be sensitive to these allergens, once applying the strict criteria for diagnosis of an actual food allergy, almost 10% of the children were considered to have food allergy.

The current study indicated that children with food allergy were more likely to have recurrent wheeze, eczema, and aeroallergen sensitization. Other risk factors for food allergy were found to include male gender, breastfeeding, and lower endotoxin exposure in the first year of life. No association was found with race/ethnicity, income, tobacco exposure, maternal stress, or early introduction of solid foods.

Reference: McGowan et al. 2014. Journal of Allergy and Clinical Immunology. DOI:10.1016/j.jaci.2014.06.033