Answer:
Pruritus is a symptom associated with a type of jaundice called obstructive jaundice. Jaundice is caused by too much bilirubin in the blood, which is a breakdown product of red blood cells. Normally the liver takes bilirubin, changes it a little, and squirts it into the intestines along with bile. When there is a blockage so that bilirubin in liver cells never makes it to the intestines, this is called obstructive jaundice.
The pathogenesis of pruritus in cholestasis (one of the causes of jaundice) is unknown but several hypotheses have been proposed, including bile acid accumulation and increased opioidergic tone.