In simplest terms, ingesting excessive amounts of nitrates can negatively affect the blood counts of your baby. The big medical term you might read for it is methemoglobinemia.
Babies suffering from methemoglobinemia will show periodic blueing of the mouth, hands, and feet. Additionally, babies may become more tired than usual or have trouble breathing. Extreme cases can cause loss of consciousness or even death. In light of that, it is important to know safety measures when feeding your baby homemade baby food.