Neonatal jaunice is a yellowing of the skin and other tissues of a newborn infant caused by the accumulation of indirect unconjugated bilirubin in the skin due to an overall increase in the total bilirubin in the blood. Neonatal jaundice is of two types: physiological or non-physiological, which is considered pathological. Physiological jaundice, which is usually harmless, is often seen in infants around the second day after birth. This usually lasts until day 8 in normal birth; in premature birth, it could last until day 14. In physiological jaundice serum bilirubin normally drops to a low level without intervention; this type of jaundice is presumably due to the lack of sufficient glucuronyl transferase, the enzyme responsible for conjugation of bilirubin prior to excretion, and it's resolved once the enzyme has been produced in sufficient quantities to allow conjugation and excretion of bilirubin as bile salts. Jaundice that appears on the first day of life is always pathologic, with bilirubin usually higher than 15mg/dL, and it's not resolved on its own.