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Background: Early life antibiotic treatment is one likely exposure influencing allergy risk. The objective was to investigate associations between pre- and postnatal antibiotic exposures and the development of allergic manifestations until age 18 months.

Methods: We included 1387 mother–child dyads from the prospective, population-based NorthPop birth cohort study. Data on antibiotic exposures in pregnancy and childhood were collected by web-based questionnaires. Until the child turned 18 months old, parents (n = 1219) reported symptoms of wheeze, eczema, and physician-diagnosed asthma; parents (n = 1025) reported physician-diagnosed food allergy. At age 18 months, serum immunoglobulin E levels to inhalant (Phadiatop) and food (Food mix fx5) allergens were determined. Associations were estimated using bivariable and multivariable logistic regressions.

Results: Prenatal antibiotic exposure was positively associated with food sensitization in the crude (OR 1.82, 95% CI 1.01–3.26) but not in the adjusted analyses (aOR 1.58, 0.82–3.05). A borderline significant association was found between prenatal exposure and wheeze (aOR 1.56, 0.95–2.57). Postnatal antibiotics were positively associated with wheeze (aOR 2.14, 1.47–3.11), asthma (aOR 2.35, 1.32–4.19), and eczema (aOR 1.49, 1.07–2.06). Postnatal antibiotics were negatively associated with food sensitization (aOR 0.46, 95% CI 0.25–0.83) but not with food allergy nor sensitization to inhalants.

Conclusion: Pre- and postnatal antibiotic exposure demonstrated positive associations with allergic manifestations and the former also with food sensitization. In contrast, there was a negative association between postnatal antibiotics and food sensitization. Food sensitization is often transient but may precede respiratory allergies. Future studies should investigate the relationship between antibiotic exposure and food sensitization later in childhood.