Recently, the focus of allergy treatment has changed from prevention to tolerance induction, and hyposensitization using Specific Oral Tolerance Induction (SOTI) for food allergy and SubLingual ImmunoTherapy (SLIT) for hay fever have been attracting attention. We found that food proteins ingested maternally exist as IgA immune complexes in breast milk, thereby inducing oral tolerance in the offspring. Breast milk is typically the first meal for humans, and may thus represent the first natural drinkable vaccination against food allergens for babies. In this report, evidence supporting this hypothesis and recent knowledge regarding its application are reviewed. We hope that this report will stimulate the re-evaluation of breast-feeding based on the mammalian origin.