Model released. For editorial use only. Newborn baby undergoing phototherapy with visible blue light in order to treat jaundice. Neonatal jaundice consists of yellowing of the skin and whites of the eyes due to the accumulation of bilirubin, a bile pigment, in the blood. It is a common condition in babies especially for premature ones. It is usually caused by immaturity of the liver which does not excrete bilirubin efficiently. The light causes the chemical breakdown of bilirubin which is then excreted in the urine. The infant's eyes have to be shielded and the treatment may last for 12 hours or more.