title: Domestic dog exposure at birth reduces the incidence of atopic dermatitis.
abstract: While the etiopathogenesis of atopic dermatitis is complex and poorly understood, neonatal exposures are important for disease occurrence. However, the effect of dog exposure on the risk of atopic dermatitis is unresolved.
  
  
  
  We investigated whether domestic dog exposure affected the risk of atopic dermatitis in children during the first 3 years of life.
  
  
  
  Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) are ongoing prospective clinical birth cohort studies. Data from 411 children born to mothers with asthma (COPSAC2000) and 700 unselected children (COPSAC2010) were analyzed following the same protocols at the same research site. Atopic dermatitis was diagnosed prospectively according to the Hanifin-Rajka criteria. Parental history of asthma, eczema, or rhinitis was defined by self-reported physician diagnosis. In the COPSAC2000, maternal specific serum IgE against eight inhalant allergens was sampled after the children's birth and at pregnancy week 24 in the COPSAC2010cohort. Associations between dog exposure and atopic dermatitis were analyzed by Cox proportional hazard regression models and adjusted for lifestyle confounders.
  
  
  
  In the COPSAC2000and COPSAC2010cohorts, the risk of atopic dermatitis was significantly lower in children with domestic dog exposure (adjustedHR = 0.46 [0.25-0.87], P = 0.02; andadjustedHR = 0.58 [0.36-0.93], P = 0.03, respectively). The risk of atopic dermatitis decreased in a dose-dependent manner with increasing number of dogs (adjustedHR = 0.58 [0.38-0.89], P = 0.01) in the COPSAC2010. The protective effect was restricted to children born to mothers with atopic disease in the unselected COPSAC2010cohort (adjustedHR = 0.39 [0.19-0.82], P = 0.01), as no effect was observed in children born to mothers without atopic disease (adjustedHR = 0.92 [0.49-1.73], P = 0.79). Paternal atopic status did not affect the risk of atopic dermatitis. We found no significant interaction between the CD14 T/T genotype and domestic dog exposure in either cohort (COPSAC2000, P = 0.36; and COPSAC2010cohort, P = 0.42).
  
  
  
  Neonatal domestic dog exposure was associated with a strongly reduced risk of atopic dermatitis in two independent birth cohorts and in a dose-dependent manner. While the mechanisms involved are unclear, our findings raise the question of whether in utero exposures may affect the risk of atopic dermatitis and emphasize the importance of the early environment for disease trajectory.
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: S
authors.initials: S
authors.lastname: Thorsteinsdottir
authors.affiliation: Department of Dermatology and Allergy, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: J P
authors.initials: JP
authors.lastname: Thyssen
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Stokholm
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: N H
authors.initials: NH
authors.lastname: Vissing
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Waage
authors.affiliation: COPSAC, Copenhagen Prospective Studies on Asthma in Childhood, Herlev and Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors.forename: H
authors.initials: H
authors.lastname: Bisgaard
mesh_terms: D000367:Age Factors; D000818:Animals; D000829:Animals, Domestic; D001249:Asthma / Q000453:epidemiology / Q000209:etiology; D003876:Dermatitis, Atopic / Q000453:epidemiology* / Q000209:etiology*; D004285:Dogs; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D000091344:Filaggrin Proteins; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D007114:Immunization; D007073:Immunoglobulin E / Q000276:immunology; D015994:Incidence; D007381:Intermediate Filament Proteins / Q000235:genetics; D053208:Kaplan-Meier Estimate; D018950:Lipopolysaccharide Receptors / Q000235:genetics; D008137:Longitudinal Studies; D008297:Male; D009154:Mutation
chemical_list: D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; D018950:Lipopolysaccharide Receptors; D007073:Immunoglobulin E
keywords: atopic dermatitis; dog; pediatrics; perinatal exposures; risk factor