Purpose: Early exposure to vaccines and antibiotics may increase the risk of developing atopy by protecting against infectious agents and reducing duration and severity of infections (the hygiene hypothesis). It may also shift the developing immune system towards a more allergic response. We assess possible associations in young allergy clinic patients.

Methods: We conducted a case-control study of 6- to 16-year-old new allergy clinic patients who were skin tested for inhalant allergens during 1987-2001 and enrolled in KPNW since birth (n = 1074). Atopic cases had positive tests for at least one inhalant allergen. Non-atopic controls had negative tests for all inhalant allergens. Using logistic regression analysis, we estimated atopy odds ratios for vaccine and antibiotic exposure variables and associations between vaccine and antibiotic exposures during the first 2 years of life and subsequent new allergy diagnoses.

Results: Atopy was not significantly associated with numbers of vaccine and antigen doses, or number of different antigens during the first 2 years of life. Number of antibiotic prescriptions was negatively associated with atopy risk. Neither exposure was significantly associated with risk of new allergy diagnoses in atopic children.

Conclusions: Atopy development appears to be unrelated to early vaccine exposure. Frequency of antibiotic prescriptions during early life, a proxy for infection frequency, appears to protect against allergic sensitization. Neither vaccines nor antibiotics appear to induce subsequent allergic reactions in atopic children.