title: Potential mechanisms for the association between fall birth and food allergy.
abstract: BACKGROUND
  Season of birth has been reported as a risk factor for food allergy, but the mechanisms by which it acts are unknown.
  
  
  METHODS
  Two populations were studied: 5862 children from the National Health and Nutrition Examination Survey (NHANES) III and 1514 well-characterized food allergic children from the Johns Hopkins Pediatric Allergy Clinic (JHPAC). Food allergy was defined as self-report of an acute reaction to a food (NHANES), or as milk, egg, and peanut allergy. Logistic regression compared fall or nonfall birth between (i) food allergic and nonallergic subjects in NHANES, adjusted for ethnicity, age, income, and sex, and (ii) JHPAC subjects and the general Maryland population. For NHANES, stratification by ethnicity and for JHPAC, eczema were examined.
  
  
  RESULTS
  Fall birth was more common among food allergic subjects in both NHANES (OR, 1.91; 95% CI, 1.31-2.77) and JHPAC/Maryland (OR, 1.31; 95% CI, 1.18-1.47). Ethnicity interacted with season (OR, 2.34; 95% CI, 1.43-3.82 for Caucasians; OR, 1.19; 95% CI, 0.77-1.86 for non-Caucasians; P = 0.04 for interaction), as did eczema (OR, 1.47; 95% CI, 1.29-1.67 with eczema; OR, 1.00; 95% CI, 0.80-1.23 without eczema; P = 0.002 for interaction).
  
  
  CONCLUSIONS
  Fall birth is associated with increased risk of food allergy, and this risk is greatest among those most likely to have seasonal variation in vitamin D during infancy (Caucasians) and those at risk for skin barrier dysfunction (subjects with a history of eczema), suggesting that vitamin D and the skin barrier may be implicated in seasonal associations with food allergy.
authors.affiliation: Division of Allergy and Immunology, Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21202, USA. ckeet1@jhmi.edu
authors.forename: C A
authors.initials: CA
authors.lastname: Keet
authors.forename: E C
authors.initials: EC
authors.lastname: Matsui
authors.forename: J H
authors.initials: JH
authors.lastname: Savage
authors.forename: D L
authors.initials: DL
authors.lastname: Neuman-Sunshine
authors.forename: J
authors.initials: J
authors.lastname: Skripak
authors.forename: R D
authors.initials: RD
authors.lastname: Peng
authors.forename: R A
authors.initials: RA
authors.lastname: Wood
mesh_terms: D002648:Child; D004485:Eczema / Q000150:complications / Q000453:epidemiology; D005260:Female; D005512:Food Hypersensitivity / Q000150:complications / Q000453:epidemiology*; D006801:Humans; D008297:Male; D009749:Nutrition Surveys; D036801:Parturition / Q000276:immunology; D012307:Risk Factors; D012621:Seasons; D014807:Vitamin D
chemical_list: D014807:Vitamin D