title: Hygiene levels in a contemporary population cohort are associated with wheezing and atopic eczema in preschool infants.
abstract: BACKGROUND
  The hygiene hypothesis states that insufficient exposure to certain infectious agents during childhood increases the risk of developing asthma and atopic diseases. Improvements in hygiene levels may be partly responsible for this decline in exposure.
  
  
  OBJECTIVE
  To assess whether hygiene levels in infancy are associated with wheeze and/or atopic eczema, independent of a number of possible confounding factors.
  
  
  METHODS
  Data were gathered from the Avon Longitudinal Study of Parents and Children (ALSPAC). Parental self completion questionnaires provided symptom data on infant wheeze and atopic eczema at 0-6 months and 30-42 months, respectively. A simple hygiene score was derived using questionnaire responses at 15 months, which ranged from least hygienic to most hygienic. Multivariable logistic regression models analysed the effect of hygiene scores on health outcomes, while adjusting for a number of important confounding variables.
  
  
  RESULTS
  Increasing hygiene scores were independently associated with wheezing (OR = 1.04; 95% CI: 1.00 to 1.08) and atopic eczema (OR = 1.04; 95% CI: 1.01 to 1.07) between 30 and 42 months, but not in the first six months. The odds ratio was higher for atopic eczema if the rash was reported to have become sore and oozy (OR = 1.09; 95% CI: 1.02 to 1.16).
  
  
  CONCLUSIONS
  High levels of hygiene at 15 months of age were independently associated with wheeze and atopic eczema reported between 30 and 42 months, and there was an increased risk for children with more severe eczema during this period. The importance of hygiene in public health should not be dismissed; however, the creation of a sterile environment through excessive cleanliness may potentially be harmful to the immune system.
authors.affiliation: Unit of Paediatric and Perinatal Epidemiology, Department of Child Health, University of Bristol, UK. Andrea.Sherriff@bris.ac.uk
authors.forename: A
authors.initials: A
authors.lastname: Sherriff
authors.forename: J
authors.initials: J
authors.lastname: Golding
mesh_terms: D002675:Child, Preschool; D015331:Cohort Studies; D003876:Dermatitis, Atopic / Q000209:etiology*; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D006920:Hygiene; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D012135:Respiratory Sounds / Q000209:etiology*