Treatment of infants with bright lights to lower the blood bilirubin level and decrease jaundice. Phototherapy works by chemically changing the bilirubin to a form that is easier for the liver to get rid of. Shining light on the skin of infants effectively reduces the amount of bilirubin in the baby's system. Light therapy is usually used only for a few days. As the baby's liver matures after birth, it is able to remove the bilirubin from the body and the light therapy is no longer needed.