Antibiotic use in early life and development of allergic diseases: respiratory infection as the explanation.

Background: Early antibiotic use has been postulated to increase the development of allergic disease. Antibiotic use results from infection. Early infection may play a confounding role in the relationship between antibiotic use and allergic disease.

Objective: We aimed to investigate the relationship between antibiotic use during the first year of life and the development of allergic diseases in a birth cohort study, and also to carefully address the confounding effect of early respiratory infection.

Methods: Three thousand three hundred and six children were included in this study who participated in investigations at all occasions of 2 months, 1, 4 and 8 years of age. Data on antibiotic use and respiratory infections were collected at the age of 1 year. Diagnoses of allergic diseases at 4 and 8 years of age were derived from the follow-up questionnaires.

Results: During the first year of life, 43% (n=1420) of the children received antibiotics and 32% (n=1046) of the children had at least one type of respiratory infection among pneumonia, bronchitis and otitis. In univariate logistic regression analysis and after adjustment for early life factors, antibiotic use during the first year of life was associated with wheeze, asthma, eczema and food hypersensitivity at 4 years of age. After adjustment for the above respiratory infections during the first year of life, only the associations with wheeze and asthma at age 4 years remained statistically significant. These associations became non-significant in a subgroup analysis in children without early allergic signs. At age 8 years, antibiotic use during the first year of life was significantly associated with wheeze and eczema after adjustment for early life factors. The significant associations at age 8 years faded away following further adjustment for the respiratory infections.

Conclusion: Our study indicated that the association between early antibiotic use and later allergic disease could at least partially be explained by early respiratory infection.