Can you elaborate what part of the skin turns blue? Cyanosis is a bluish discoloration of the skin or mucous membranes caused by lack of oxygen in the blood. People whose blood is deficient in oxygen tend to have a bluish discoloration. Usually the oxygen saturation of the blood has to drop below 90% before this occurs.
It is more obvious in the mucous membranes and nail beds, particularly in dark-skinned people. It may also appear on the feet, nose