title: Childhood antecedents of allergic sensitization in young British adults.
abstract: OBJECTIVE
  This study was designed to investigate whether associations of self-reported hay fever with sibship size, birth order, infant feeding, and childhood socioeconomic status reflect variations in sensitization to common aeroallergens.
  
  
  METHODS
  One thousand three hundred sixty-nine persons born throughout Britain in 1958 were followed up to age 34 to 35 years. The cohort included 1050 subjects with a history of asthma, wheezy bronchitis, wheezing, or pneumonia and 319 with no history of wheezing illness at ages 7, 11, 16, 23, or 33 years. Skin prick tests with extracts of mixed grass pollen, house dust mite (Der p 1), and cat fur were performed; and wheal diameters were measured.
  
  
  RESULTS
  The prevalence of positive skin test results (> or = 3 mm wheal) was independently related (p < 0.01) to male sex, reduced numbers of older siblings (but not younger siblings), and higher socioeconomic status in childhood. Current cigarette smoking and maternal smoking during pregnancy were independently associated (p < 0.01) with a reduced prevalence of skin prick test positivity. No significant independent effects (p > 0.10) were found for adult social class, maternal age, birth weight, gestation, breast feeding, preschool nursery attendance, urban birthplace, or gas stove exposure.
  
  
  CONCLUSIONS
  Factors related to small families and relative affluence in childhood promote atopic sensitization to a variety of aeroallergens in later life. These observations are consistent with the suggestion that early infection may protect against subsequent allergic disease.
authors.affiliation: Department of Public Health Sciences, St. George's Hospital Medical School, London, United Kingdom.
authors.forename: D P
authors.initials: DP
authors.lastname: Strachan
authors.forename: L S
authors.initials: LS
authors.lastname: Harkins
authors.forename: I D
authors.initials: ID
authors.lastname: Johnston
authors.forename: H R
authors.initials: HR
authors.lastname: Anderson
mesh_terms: D000328:Adult; D001722:Birth Order; D005191:Family Characteristics; D005260:Female; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000453:epidemiology* / Q000276:immunology; D007114:Immunization; D008297:Male; D011247:Pregnancy; D015995:Prevalence; D012801:Sibling Relations; D012882:Skin Tests; D012959:Socioeconomic Factors; D006113:United Kingdom / Q000453:epidemiology