Skin coloration is determined by the amount of pigment in the skin and the red blood flowing beneath it. Blood that is saturated with oxygen is bright red. Blood that has lost its oxygen is dark bluish-red. People who have a high percentage of their blood which is deficient in oxygen tend to take on a bluish discoloration called cyanosis. Most cyanosis is seen as a result of congenital heart disease , pulmonary disease , or as a terminal event as in cardiopulmonary arrest.
Mild cyanosis is difficult to detect.
Cyanosis is more obvious in the mucous membranes and nail beds, particularly for dark-skinned people. It can also appear on the feet, nose, and ears. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as location, quality, time course, aggravating factors, relieving factors, and associated complaints.