The word jaundice comes from the French word jaune, meaning yellow. Neonatal jaundice – the yellowing of a baby’s skin within a few days of birth – can be alarming for parents, but it’s usually easily resolved.

The yellow color comes from an excess of bilirubin, a yellowish-red pigment that’s released into the bloodstream naturally when red blood cells break down. Newborns have lots of red blood cells, resulting in lots of bilirubin in the blood. Normally, the liver processes bilirubin as blood flows through this versatile organ, but sometimes the immature liver of a newborn can’t process fast enough. Bilirubin then accumulates in the tissues, giving skin the telltale yellow hue of jaundice. The situation sometimes resolves on its own, or can be corrected with special lights (‘bili lights’) or fiberoptic phototherapy blankets that emit light at a wavelength that converts bilirubin into a water-soluble form that’s excreted in the urine. After a few days, the newborn’s liver matures enough to be able to process the bilirubin without assistance.