Abstract

P Cullinan, JM Harris, P Mills, S Moffat, C White, J Figg, A Moon, M Barnes, AJ Newman Taylor
Occupational and Environmental Medicine, Imperial College of Medicine (NHLI), London, UK.

Surveys which show that atopic disease is more common in smaller families suggest that early life infections may offer protection. We report results from a cross-sectional study of adults from SE England, undertaken as a test of this hypothesis. A total of 1063 adults (93% of those eligible) completed a questionnaire and underwent skin prick testing with common aeroallergens and venepuncture for specific IgG antibodies to Helicobacter pylori and Hepatitis A, infections believed to have their highest incidence in early childhood. 392 (37%) adults had an immediate skin test reaction to at least one of the three common allergens; 151 (17%) and 78 (9%) had antibodies to H. pylori and Hepatitis A respectively. Few adults (4%) were only-children and odds ratios were expressed in relation to one or no siblings. The prevalence of atopy decreased linearly with family size (OR 0.85 for each sibling), a pattern which remained significant (p=0.001) after adjusting for age, male sex, and social class. The prevalence of H. pylori and Hepatitis A antibodies increased with family size, OR 1.30, 95% ci (1.16, 1.46) and OR 1.19 (1.04, 1.37) per sibling respectively. However there were no significant relationships between atopy and the presence of either H.pylori (p=0.60) or Hepatitis antibodies (p=0.92). The findings from these indicators do not support the hypothesis that poor hygiene in early life confers protection against subsequent atopy.