Background: It is suggested that the inverse relationship between allergic disease and family size reflects reduced exposure to early life infections, and that antibiotic treatment in childhood diminishes any protective effect of such infection.
Methods: A birth cohort study was undertaken in 642 children recruited before birth and seen annually until the age of 8 years. Reported infections and prescribed antibiotics by the age of 5 years were counted from GP records and comparisons were made with a previous study of their parents.
Results: At the age of 8 years, 104 children (19%) were atopic, 79 (13%) were currently wheezy and 124 (21%) had seasonal rhinitis. 577 children (97%) had at least three infections recorded by age 5, a figure much higher than that of their parents (69%). By the age of 5 only 11 children (2%) had never received a prescription for antibiotics; the corresponding figure for the parents was 24%. Higher numbers of infections were recorded for firstborn children. After adjusting for parental atopy and birth order, there was no association between infection counts and atopy (OR 1.01 (95% CI 0.99 to 1.03) per infection). Significant positive associations were found for wheeze and seasonal rhinitis. An increased risk of current wheeze was found for each antibiotic prescription (adjusted OR 1.07 (95% CI 1.03 to 1.10)) but not for atopy. This was primarily explained by prescriptions for respiratory infections. Similar patterns were observed for seasonal rhinitis.
Conclusions: Despite very high rates of recorded early life infections and antibiotic prescriptions, no plausibly causative relationships were found with subsequent respiratory allergies.