Light therapy, also called phototherapy, exposes infants with jaundice, a yellowing of the skin and eyes, to artificial or natural light to break down the buildup of bilirubin pigment in the blood. Bilirubin is an orange to red pigment produced when red blood cells break down, which causes infants to turn into a yellowish color. Small amounts of bilirubin in the blood are normal, but when there is an accumulation of excess bilirubin pigment, the body deposits the excess bilirubin in the layer of fat beneath the skin. That accumulation of bilirubin causes the skin and the white areas of the eye to appear yellowed, a common symptom of jaundice. Buildup of bilirubin typically occurs when the immature liver of a newborn infant is unable to efficiently breakdown the bilirubin molecule into products that the body can excrete. High levels of bilirubin, a phenomenon called hyperbilirubinemia can be toxic and can lead to a brain dysfunction called kernicterus, which may result in permanent brain damage. The relative simplicity of phototherapy treatment has made effective neonatal jaundice treatment nearly universal, almost completely eliminating the risk of infant brain damage from hyperbilirubinemia.

Jerold Lucey studied newborn infants in the United States in the twentieth century. In the 1960s and 1970s, Lucey studied phototherapy as a treatment for jaundice, a condition in infants whose livers cannot excrete broken down red blood cells, called bilirubin, into the bloodstream at a fast enough rate. In addition to his work in jaundice, Lucey was the editor in chief for the journal Pediatrics of the American Academy of Pediatrics. Lucey helped establish standards of care for several neonatal conditions, including neonatal jaundice and infant respiratory distress disorder (also called hyaline membrane disorder).

Neonatal jaundice is the yellow discoloration of the skin and eyes due to elevated bilirubin levels in the bloodstream of a newborn. Bilirubin is a byproduct of the breakdown of red blood cells. Jaundiced infants are unable to process bilirubin at a normal rate or they have an abnormally high amount of bilirubin in their bloodstream, resulting in a buildup of the yellow colored bilirubin. That build up is called hyperbilirubinemia and is the cause of jaundice. Jaundice can lead to kernicterus, a rare neurological disorder that results in hearing loss, permanent brain damage, and sometimes death. Research into the causes of jaundice and kernicterus began in the late eighteenth century in Paris, France. By the middle of the twentieth century, scientists developed treatments for jaundice that successfully treated infants afflicted with the condition, phototherapy and blood exchange transfusion, due to these treatments, the risk for an infant in developing kernicterus is very low.

In 1968, pediatric researchers Jerold Lucey, Mario Ferreiro, and Jean Hewitt conducted an experimental trial that determined that exposure to light effectively treated jaundice in premature infants. The three researchers published their results in 'Prevention of Hyperbilirubinemia of Prematurity by Phototherapy' that same year in Pediatrics. Jaundice is the yellowing of the skin and eyes due to the failure of the liver to break down excess bilirubin in the blood, a condition called hyperbilirubinemia. Bilirubin is a product that results from the degradation of red blood cells, which the immature liver of premature infants often has difficulty breaking down. Lucey's group's study demonstrated both the efficacy of phototherapy, which uses light to breakdown the bilirubin in the blood, as treatment for hyperbilirubinemia. As a result of Lucey's research team's study, physicians adopted phototherapy as the standard of care for treating premature infants born with jaundice.