In breast milk, there are substances responsible for protection against infections, such as lactoperoxidase, lysozyme, lactoferrin, catalase, superoxide dismutase, glutathione peroxidase, secretory immunoglobulins (SIgA), immunoglobulins IgM, IgG, IgD, interleukins, especially IL-4, IL-10, IL-12, IL-18, growth factors, i.e., epidermal growth factor (EGF), insulin-like growth factor-I (IGF-1), nerve growth factor (NGF), transforming growth factor α and β (TGF α and β) [18]. Here, LPO is linked to infection.