title: Endotoxin levels in Estonian and Swedish house dust and atopy in infancy.
abstract: BACKGROUND
  Immune responses, including those to allergens, may be T helper (Th)2 skewed in newborns. In order to redress the fetal Th1/Th2 imbalance, Th1-stimulating factors, such as bacterial endotoxin, may be required. The increasing prevalence and severity of atopic diseases in industrialized countries, which are in marked contrast with the low prevalence of allergy among children in the formerly socialist countries of Europe, have been suggested to be caused by a reduced microbial stimulation.
  
  
  OBJECTIVE
  To relate the endotoxin levels in house dust from two countries with a low (Estonia) and a high (Sweden) prevalence of allergy to the development of atopic disease and sensitization in the children during the first 2 years of life.
  
  
  METHODS
  The study included 108 children from Tartu, Estonia and 111 children from Linköping, Sweden. Skin prick tests were performed at 3, 6, 12 and 24 months of age, and questionnaires were distributed to the families. At 24 months, a paediatrician examined the children. Dust samples were collected from mattresses and carpets and the endotoxin concentration was determined by a chromogenic Limulus assay.
  
  
  RESULTS
  The endotoxin levels were higher in Estonian than in Swedish house dust (median levels 29 (range 0.25-280) and 14 (range 0.25-99) EU/mg dust, respectively, P < 0.001). Furthermore, the levels were inversely related to the development of atopic disease and sensitization in the Swedish, but not in the Estonian, children.
  
  
  CONCLUSIONS
  The low prevalence of atopic disease in Estonia may, at least in part, be related to the high endotoxin levels in this country. The findings support that high levels of endotoxin, or other bacterial products with Th1-stimulating properties, might protect children from developing atopic disease.
authors.affiliation: Department of Molecular and Clinical Medicine, Division of Paediatrics and Clinical Research Centre, Faculty of Health Sciences, Linköping University, S-881-85 Linköping, Sweden. malfa@imk.liu.se
authors.forename: M F
authors.initials: MF
authors.lastname: Böttcher
authors.forename: B
authors.initials: B
authors.lastname: Björkstén
authors.forename: S
authors.initials: S
authors.lastname: Gustafson
authors.forename: T
authors.initials: T
authors.lastname: Voor
authors.forename: M C
authors.initials: MC
authors.lastname: Jenmalm
mesh_terms: D001513:Beds / Q000382:microbiology; D002675:Child, Preschool; D004391:Dust / Q000032:analysis* / Q000276:immunology; D004731:Endotoxins / Q000032:analysis* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D004957:Estonia / Q000453:epidemiology; D005260:Female; D005430:Floors and Floorcoverings; D006801:Humans; D006967:Hypersensitivity / Q000453:epidemiology* / Q000209:etiology; D007223:Infant; D016015:Logistic Models; D016017:Odds Ratio; D011247:Pregnancy; D015995:Prevalence; D011446:Prospective Studies; D012882:Skin Tests; D018709:Statistics, Nonparametric; D013548:Sweden / Q000453:epidemiology
chemical_list: D004391:Dust; D004731:Endotoxins