How can light treat jaundice?

What is SUNLIGHT? Sunlight is energy that can pass through our bony skull, skin and blood vessels to reach the brain, the blood, and liver. Light energy enters the eye and hits the retina and the rod and cone cells within it. Here it is converted into electrical energy that travels along the neurons in the optic nerves to reach the brain. What is JAUNDICE? Bilirubin is normally secreted into the bile from the blood. At birth, the liver's capacity to secrete bilirubin is not fully developed. Our body constantly produce new red blood cells. The older cells break down and release their contents in the blood. Bilirubin, that comes from the breakdown of old red blood cells, builds up in the body. High levels of bilirubin cause jaundice with yellowing of the skin and eyes. Jaundice in newborns generally lasts only a few days, but if it persists and left untreated, it can lead to a buildup of bilirubin in the brain, causing permanent brain damage.

In England, during World War II, something happened in a hospital specialized in the care of babies with jaundice. During the day, a nurse was in charge of moving the babies from their incubators to the hospital's courtyard to get some fresh air and SUNLIGHT. One day, while she was dressing a baby, she noticed that the baby's tummy was no longer yellow in the area been exposed to the sun. At that time, nobody believed that the sun could cure jaundice. But one day, a vial containing a blood sample from a jaundiced baby was accidentally left on a windowsill, in natural sunlight, for several hours. When the sample came back, the blood was normal. The doctors investigated further to find that the excess bilirubin in the sample had somehow been broken down. The blood in the vial now had normal bilirubin levels. Since then, sunlight was introduced in mainstream to treat jaundice in babies.

​References Doidge, Norman. The brain's way of healing: stories of remarkable recoveries and discoveries. Penguin UK, 2015. Vander, Arthur J., et al. Human Physiology: The Mechanisms of Body Function. 8th ed., McGraw-Hill, 2001.