Background: Evidence on the association between antibiotics and the risk of food allergies is limited. We explored the associations between mother's and offspring's use of antibiotics and the risk of cow's milk allergy in infancy.
Methods: We used a national registry to identify all children who were born in 1996-2004 in Finland and diagnosed with cow's milk allergy after 1 month of age by November 2005 (n = 15,672). For each case, we selected one control matched for birth date, sex, and hospital district. Information on antibiotic purchases and putative confounders was obtained from registries. The associations were analyzed using conditional logistic regression.
Results: Maternal use of antibiotics before and during pregnancy was associated with an increased risk of cow's milk allergy in the offspring (odds ratio = 1.26 [95% confidence interval = 1.20-1.33] and 1.21 [1.14-1.28], respectively, adjusting for putative confounders). The risk of cow's milk allergy increased with increasing number of child's antibiotics used from birth to diagnosis (test for trend P < 0.001).
Conclusions: Both maternal and child's use of antibiotics were associated with an increased risk of cow's milk allergy. Future studies are needed to confirm these novel findings and to explore the potential biologic mechanisms behind the association.