What is melamine? Melamine is a white, crystalline powder made from urea, a readily available raw material that is produced from ammonia and carbon dioxide. More than 95% of melamine production worldwide is used as a raw material to make amino-formaldehyde resins. In addition, melamine is known to be excreted in animal urine, and believed not to accumulate in the body of animals. When exposure levels are much higher, as was the case with cats and dogs, the melamine and its compounds appear to cause the formation of crystals in the kidney systems, resulting in kidney damage.

Melamine alone is of low toxicity, however animal studies have suggested that kidney problems occur when melamine is present in combination with cyanuric acid, a potential impurity of melamine. This combination has formed crystals in the body and was not fully dissolved in urine, the melamine gathered in the kidney, gunking up the organ and forming stones. The level of melamine found in the contaminated infant formula has been as high as 2 560 miligram per kilogram ready-to-eat product, while the level of cyanuric acid is unknown.

In 2007, melamine was found in wheat gluten and rice protein concentrate exported from China and used in the manufacture of pet food in the US. This caused the death of a large number of dogs and cats due to kidney failure. By itself, melamine is not known to be highly toxic, so scientific investigators now think it is a mixture of melamine and another chemical—cyanuric acid—added to the Chinese wheat flour that is causing crystal formation in the kidneys of cats, dogs and other domesticated animals.