Jaundice occurs in many newborn babies and is not harmful if treated properly. Jaundice occurs because there is too much bilirubin in the blood. Bilirubin is a yellow substance, which is why it causes a yellow discoloration. Bilirubin can leave the body through urine or stool (hence the yellow color of urine). If there is too much bilirubin in the blood, your baby needs help to eliminate the excess bilirubin through urine or stool. Breaking bilirubin into smaller pieces makes it easier to excrete through urine or stool. Blue light helps break down bilirubin into smaller pieces.