title: Perinatal cat and dog exposure and the risk of asthma and allergy in the urban environment: a systematic review of longitudinal studies.
abstract: BACKGROUND
  The literature is contradictory concerning pet exposure and the risk of development of asthma and other allergic diseases. Using longitudinal studies, we aimed to systematically review the impact of pet ownership in the critical perinatal period as a risk factor for allergies in childhood.
  
  
  METHODS
  Medline database was searched for urban cohort studies with perinatal exposure to cats and/or dogs and subsequent asthma or allergic disease.
  
  
  RESULTS
  Nine articles, comprising 6498 participants, met inclusion criteria. Six found a reduction in allergic disease associated with perinatal exposure to dogs or, cats or dogs. One study found no association. Two found increased risk only in high-risk groups.
  
  
  CONCLUSIONS
  Longitudinal studies in urban populations suggest that perinatal pets, especially dogs, may reduce the development of allergic disease in those without a family history of allergy. Other unmeasured factors such as pet-keeping choices in allergic families may be confounding the association seen in these high-risk families, and further study is required.
authors.affiliation: Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, School of Population Health, University of Melbourne, Melbourne, Vic 3010, Australia. clodge@unimelb.edu.au
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Lodge
authors.forename: Katrina J
authors.initials: KJ
authors.lastname: Allen
authors.forename: Adrian J
authors.initials: AJ
authors.lastname: Lowe
authors.forename: David J
authors.initials: DJ
authors.lastname: Hill
authors.forename: Cliff S
authors.initials: CS
authors.lastname: Hosking
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Abramson
authors.forename: Shyamali C
authors.initials: SC
authors.lastname: Dharmage
mesh_terms: D000485:Allergens / Q000276:immunology*; D000818:Animals; D001249:Asthma / Q000209:etiology* / Q000276:immunology*; D002415:Cats; D004285:Dogs; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008137:Longitudinal Studies; D018811:Maternal Exposure / Q000009:adverse effects*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000209:etiology / Q000276:immunology; D018570:Risk Assessment; D012307:Risk Factors
chemical_list: D000485:Allergens