Season of birth and food allergy in children

Background: The prevalence of food allergy is rising, and etiologic factors remain uncertain. Evidence implicates a role for vitamin D in the development of atopic diseases. Based on seasonal patterns of UV-B exposure (and consequent vitamin D status), we hypothesized that patients with food allergy are more often born in fall or winter. Objective: To investigate whether season of birth is associated with food allergy. Methods: We performed a multicenter medical record review of all patients presenting to 3 Boston emergency departments (EDs) for food-related acute allergic reactions between January 1, 2001, and December 31, 2006. Months of birth in patients with food allergy were compared with that of patients visiting the ED for reasons other than food allergy. Results: We studied 1002 patients with food allergy. Of younger children with food allergy (age <5 years), but not older children or adults, 41% were born in spring or summer compared with 59% in fall or winter (P=.002). This approximately 40: 60 ratio differed from birth season in children treated in the ED for non-food allergy reasons (P=.002). Children younger than 5 years born in fall or winter had a 53% higher odds of food allergy compared with controls. This finding was independent of the suspected triggering food and allergic comorbidities. Conclusions: Food allergy is more common in Boston children born in the fall and winter seasons. We propose that these findings are mediated by seasonal differences in UV-B exposure. These results add support to the hypothesis that seasonal fluctuations in sunlight and perhaps vitamin D may be involved in the pathogenesis of food allergy. Ann Allergy Asthma Immunol. 2010;104:307-313.