Bilirubin is a by-product of the destruction of red blood cells in the spleen. Bilirubin is processed by the liver into a water soluble form that is then expelled through the bile duct into the intestines where it passes in waste.
Hyperbilirubinaemia, or jaundice, is the result of a buildup of bilirubin in the bloodstream. It is usually a sign of a serious illness in adults, but is normal in newborn infants. Newborns often re-absorb bilirubin through the intestine until their diet improves, raising the bilirubin levels in the body. However, on occasion, this can lead to kernicterus, a potentially life threatening condition.
Bilirubin breaks down under light and in cases of infantile jaundice infants are often put under bright lights to reduce their bilirubin levels.