title: Exposure to endotoxin or other bacterial components might protect against the development of atopy.
abstract: BACKGROUND
  Several recent studies have shown that growing up on a farm confers significant protection against the development of atopy. These findings point particularly towards the importance of exposure to stable dust and farm animals. It has furthermore been reported that endotoxin, an intrinsic part of the outer membrane of gram negative bacteria, is abundant in environments where livestock and poultry is kept. The aim of this study was therefore to measure the level of environmental endotoxin exposure in homes of farmers' children, children with regular contact to livestock and control children with no contact to farm animals.
  
  
  METHODS
  Eighty-four farming and nonfarming families were identified in rural areas in Southern Germany and Switzerland. Samples of settled and airborne dust were collected in stables, and of settled dust indoors from kitchen floors and the children's mattresses. Endotoxin concentrations were determined by a kinetic Limulus assay.
  
  
  RESULTS
  Endotoxin concentrations were highest in stables of farming families, but were also significantly higher indoors in dust from kitchen floors (143 EU/mg vs 39 EU/mg, P < 0.001) and children's mattresses (49479 EU/m2 vs 9383 EU/m2, P < 0.001) as compared to control children from nonfarming families. In addition, endotoxin levels were also significantly higher in mattresses and dust from kitchen floors in households where children had regular contact to farm animals (38.6 EU/mg and 23340 EU/m2, respectively) as compared to control subjects.
  
  
  CONCLUSIONS
  We propose that the level of environmental exposure to endotoxin and other bacterial wall components is an important protective determinant for the development of atopic diseases in childhood.
authors.affiliation: University Children's Hospital Munich, Germany; Institute of Social and Preventive Medicine, University of Basel, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: von Mutius
authors.forename: C
authors.initials: C
authors.lastname: Braun-Fahrländer
authors.forename: R
authors.initials: R
authors.lastname: Schierl
authors.forename: J
authors.initials: J
authors.lastname: Riedler
authors.forename: S
authors.initials: S
authors.lastname: Ehlermann
authors.forename: S
authors.initials: S
authors.lastname: Maisch
authors.forename: M
authors.initials: M
authors.lastname: Waser
authors.forename: D
authors.initials: D
authors.lastname: Nowak
mesh_terms: D000293:Adolescent; D001513:Beds; D002648:Child; D002675:Child, Preschool; D004391:Dust / Q000032:analysis; D004731:Endotoxins / Q000032:analysis / Q000276:immunology*; D005430:Floors and Floorcoverings; D006798:Housing; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology / Q000517:prevention & control*; D007223:Infant; D012424:Rural Population
chemical_list: D004391:Dust; D004731:Endotoxins