What is the condition called when skin turns blue due to a lack of oxygen?

The condition where skin turns blue due to a lack of oxygen is known as cyanosis. This occurs when there is insufficient oxygen in the blood, causing a bluish discoloration of the skin and mucous membranes. Cyanosis can be a critical indicator of respiratory or circulatory issues, signifying that the body's tissues may not be receiving adequate oxygenation. It is often observed in patients with respiratory distress, heart problems, or conditions that impair oxygen exchange.

The other conditions listed are distinct and do not pertain to the lack of oxygen. Jaundice is characterized by a yellowing of the skin and eyes due to elevated bilirubin levels, often a sign of liver dysfunction. Pallor refers to an abnormal paleness of the skin, which may result from various factors like anemia or shock, but it is not associated with the blue discoloration seen in cyanosis. Hyperemia is an increase in blood flow to a particular area of the body, which can cause redness, rather than a bluish tint. Thus, cyanosis is specifically associated with the observable effect of low oxygen in the blood.