title: Pet exposure and risk of atopic dermatitis at the pediatric age: a meta-analysis of birth cohort studies.
abstract: BACKGROUND
  Findings on pet exposure and the risk of atopic dermatitis (AD) in children are inconsistent.
  
  
  OBJECTIVE
  With the aim to summarize the results of exposure to different pets on AD, we undertook a meta-analysis of epidemiologic studies on this issue.
  
  
  METHODS
  In August 2012, we conducted a systematic literature search in Medline and Embase. We included analytic studies considering exposure to dogs, cats, other pets, or pets overall during pregnancy, infancy, and/or childhood, with AD assessment performed during infancy or childhood. We calculated summary relative risks and 95% CIs using both fixed- and random-effects models. We computed summary estimates across selected subgroups.
  
  
  RESULTS
  Twenty-six publications from 21 birth cohort studies were used in the meta-analyses. The pooled relative risks of AD for exposure versus no exposure were 0.72 (95% CI, 0.61-0.85; I(2) = 46%; results based on 15 studies) for exposure to dogs, 0.94 (95% CI, 0.76-1.16; I(2) = 54%; results based on 13 studies) for exposure to cats, and 0.75 (95% CI, 0.67-0.85; I(2) = 54%; results based on 11 studies) for exposure to pets overall. No heterogeneity emerged across the subgroups examined, except for geographic area.
  
  
  CONCLUSIONS
  This meta-analysis reported a favorable effect of exposure to dogs and pets on the risk of AD in infants or children, whereas no association emerged with exposure to cats.
authors.affiliation: IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy. Electronic address: claudio.pelucchi@marionegri.it.
authors.forename: Claudio
authors.initials: C
authors.lastname: Pelucchi
authors.affiliation: IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy; Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
authors.forename: Carlotta
authors.initials: C
authors.lastname: Galeone
authors.affiliation: Université Paris Descartes, INSERM, Paris, France; INSERM, Unité 1013, Paris, France.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Bach
authors.affiliation: IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy; Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: La Vecchia
authors.affiliation: IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
authors.forename: Liliane
authors.initials: L
authors.lastname: Chatenoud
mesh_terms: D000818:Animals; D002415:Cats / Q000276:immunology*; D015331:Cohort Studies; D003876:Dermatitis, Atopic / Q000453:epidemiology*; D004285:Dogs / Q000276:immunology*; D004781:Environmental Exposure; D006801:Humans; D057805:Pets / Q000276:immunology*; D012306:Risk
keywords: AD; Atopic dermatitis; OR; Odds ratio; RR; Relative risk; child; epidemiology; hygiene hypothesis; pets