It emerged that the intake of L. salivarius PS2 in the mastitis group led to a reduction in bacterial counts and IL-8 levels in milk and leukocyte counts in milk and blood, and to an increase in IgE levels and IgG, epidermal growth factor (EGF), and transforming growth factor-β (TGF-β2) levels in breast milk. This evidence concerns the gene IGHE and mastitis.