title: Age of entry to day nursery and allergy in later childhood.
abstract: BACKGROUND
  Infections in early childhood may prevent allergies in later life. If this hypothesis is true, early exposure to childcare outside the home would protect against atopy by promotion of cross infections. We investigated whether children who attend a nursery at a young age have a lower rate of atopy and fewer allergies than children who attend from an older age.
  
  
  METHODS
  In a cross-sectional study carried out in 1992-93, we examined 2471 children in three age-groups (5-7, 8-10, and 11-14 years) from the towns of Bitterfeld, Hettstedt, and Zerbst in eastern Germany. The children's parents answered a questionnaire about allergies and symptoms, attendance at day care, and related factors. Sensitisation was assessed by skin-prick tests and measurement of allergen-specific IgE antibodies in serum.
  
  
  RESULTS
  In 669 children from small families (up to three people), the prevalence of atopy was higher among children who started to attend day nursery at an older age than in those who started to attend at a younger age (p<0.05). Compared with children who first attended at age 6-11 months, the adjusted odds ratios for a positive skin-prick test were 1.99 (95% CI 1.08-3.66) for children who attended at age 12-23 months and 2.72 (1.37-5.40) for those who attended at age 24 months and older. In 1761 children from large families (more than three people), age of entry to day nursery had no effect on atopy.
  
  
  CONCLUSIONS
  Our findings accord with the hypothesis that early infection may protect against allergies in later life.
authors.affiliation: Medical Institute of Environmental Hygiene, Heinrich Heine University Düsseldorf, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Krämer
authors.forename: J
authors.initials: J
authors.lastname: Heinrich
authors.forename: M
authors.initials: M
authors.lastname: Wjst
authors.forename: H E
authors.initials: HE
authors.lastname: Wichmann
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000485:Allergens / Q000276:immunology; D002648:Child; D002656:Child Day Care Centers; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis* / Q000276:immunology / Q000517:prevention & control; D007109:Immunity; D007073:Immunoglobulin E / Q000097:blood; D007223:Infant; D007239:Infections / Q000276:immunology; D008297:Male; D016017:Odds Ratio; D012111:Residence Characteristics; D012307:Risk Factors; D012882:Skin Tests; D011795:Surveys and Questionnaires