Melamine caused the 2008 Chinese milk scandal and the resulting recalls of thousands of dairy products.
Some Chinese milk suppliers added melamine to diluted milk to make protein tests show artificially high readings. The chemical is nitrogen-rich, so it can make a product appear to contain more protein than it really does. Infants who consumed contaminated milk powder developed kidney problems, including kidney stones.
The scandal began with Sanlu Group products and spread to milk powder, infant formula, and foods made with contaminated dairy ingredients. Chinese authorities ordered recalls and inspections, while products were withdrawn in other countries because exported ingredients had entered international supply chains.
Melamine is an industrial chemical and is not an acceptable substitute for nutritional protein. The incident is distinct from ordinary bacterial contamination: the danger came from deliberate adulteration and the formation of crystals in the urinary system. It became a major case study in food regulation and supply-chain oversight.