title: Exposure to pets, and the association with hay fever, asthma, and atopic sensitization in rural children.
abstract: BACKGROUND
  An increasing number of studies report pet exposure to be associated with lower risk of asthma and allergies. This 'protective pet effect' has been suggested to result from a modified T-helper (Th)2-cell response, or because of increased microbial load in homes where pets are kept. We examined the associations between pet contact and the occurrence of asthma and allergies in children of the rural Allergy and Endotoxin (ALEX) population, taking farm animal contact, endotoxin and cat allergen levels in mattress dust into account.
  
  
  METHODS
  Information about contact with pets and farm animals, asthma and allergy were collected for 812 children by a standardized parents' questionnaire and an interview. Mattress dust endotoxin and cat allergen levels as well as specific IgE and IgG4 antibodies to Fel d1 were determined.
  
  
  RESULTS
  Current contact with dogs was inversely associated with diagnosed hay fever (OR 0.26, 95% CI 0.11-0.57), diagnosed asthma (OR 0.29, 95% CI 0.12-0.71), sensitization to cat allergen (OR 0.48, 95% CI 0.23-0.99) and to grass pollen (OR 0.55, 95% CI 0.33-0.94), but not with increased IgG4 levels. Early and current contact with cats were associated with reduced risk of wheezing (OR 0.48, 95% CI 0.23-1.00, and OR 0.49, 95% CI 0.26-0.92, respectively) and grass pollen sensitization. Adjustment for farm animal contact but not for endotoxin and cat allergen exposure attenuated these associations and the effect of pet was stronger among farmers' children.
  
  
  CONCLUSIONS
  Although pet exposure was very frequent in this rural population, the inverse relation between current dog contact, asthma and allergy was mostly explained by simultaneously occurring exposure to stable animals or was restricted to farm children. In addition, a subtle form of pet avoidance may contribute to the protective effect of pet.
authors.affiliation: Institute of Social and Preventive Medicine, University of Basel, Basel, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Waser
authors.forename: E
authors.initials: E
authors.lastname: von Mutius
authors.forename: J
authors.initials: J
authors.lastname: Riedler
authors.forename: D
authors.initials: D
authors.lastname: Nowak
authors.forename: S
authors.initials: S
authors.lastname: Maisch
authors.forename: D
authors.initials: D
authors.lastname: Carr
authors.forename: W
authors.initials: W
authors.lastname: Eder
authors.forename: G
authors.initials: G
authors.lastname: Tebow
authors.forename: R
authors.initials: R
authors.lastname: Schierl
authors.forename: M
authors.initials: M
authors.lastname: Schreuer
authors.forename: C
authors.initials: C
authors.lastname: Braun-Fahrländer
mesh_terms: D000818:Animals; D000829:Animals, Domestic; D001249:Asthma / Q000453:epidemiology*; D002415:Cats; D002648:Child; D003430:Cross-Sectional Studies; D004285:Dogs; D004781:Environmental Exposure; D005260:Female; D006023:Glycoproteins / Q000276:immunology; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology* / Q000276:immunology; D015994:Incidence; D008297:Male; D006109:Poaceae / Q000276:immunology; D011058:Pollen / Q000276:immunology; D011852:Radioallergosorbent Test; D006255:Rhinitis, Allergic, Seasonal / Q000453:epidemiology*; D012424:Rural Population / Q000706:statistics & numerical data*
chemical_list: D006023:Glycoproteins; C059296:Fel d 1 protein, Felis domesticus