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 Birth cohort study. 642 children were recruited before birth and seen annually until age 8; reported infections and prescribed antibiotics by age 5 years were counted from GP records. Comparisons with a previous study of their parents have been made
Results At age 8, 104 (19%) children were atopic, 79 (13%) were currently wheezy and 124 (21%) had seasonal rhinitis. 577 (97%) children had at least 3 infections recorded by age 5, a figure much higher than that of their parents (69%). By the age of 5 only 11 (2%) children 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 (odds ratio [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 [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 we have failed to find any plausibly causative relationships with subsequent respiratory allergies.
- birth order
- childhood infection