Blue baby syndrome, also known as infant methemoglobinemia, is a condition where a baby’s skin turns blue. This occurs due to a decreased amount of hemoglobin in the baby’s blood. The most common cause of blue baby syndrome is water contaminated with nitrates. After a baby drinks formula made with nitrate-rich water, the body converts the nitrates into nitrites. These nitrites bind to the hemoglobin in the body, forming methemoglobin, which is unable to carry oxygen. Nitrates are most common in drinking water in farming communities that use well water. This contamination is due to the use of fertilizers and manure.

Source: ForumIAS