The leading cause of blue skin is poor oxygen delivery to the body, a problem associated with a number of medical conditions including genetic disorders, as well as acquired conditions. Other causes can include dietary factors and exposure to toxins resulting in skin discoloration. The development of skin blueness can be a cause for medical concern, and a patient with a sudden change in skin pigmentation should seek evaluation and treatment.
When the body is not getting enough oxygen, the skin can start to turn blue, starting at the extremities. A condition called methemoglobinemia can cause congenitally blue skin by interfering with the transport of oxygen to the extremities. Likewise, people with Raynaud's phenomenon develop blue skin because their blood vessels clamp down, restricting the flow of blood to the tissues. Other causes can be respiratory disorders, as well as heart conditions, both of which make it harder for oxygen to reach the far corners of the body.
Certain toxins can cause changes in skin pigmentation, including a bluish cast to the skin. A common example is argyria, where people are exposed to high levels of silver and develop blue skin as a result. Colloidal silver supplements added to the diet in some regions can cause this condition, and in some cases, blue skin is the result of dietary factors. Isolated patches of bluish pigmentation can also be the result of situations like heavy bruising or hemorrhage just below the skin.
People who develop blue skin should take note of any other symptoms they experience, like shortness of breath, weakness, or nausea. These symptoms can be important diagnostic clues for physicians evaluating patients with skin conditions. At the doctor's office, some tests may be run to gather information about levels of dissolved oxygen in the blood, along with other factors. These tests can also be used to check for genetic conditions known to be associated with blue skin.
Treatment may resolve the discoloration and allow the patient to return to a more conventional color. In the case of circulatory problems, the restoration of healthy skin color can occur very rapidly, as the patient starts getting adequate oxygen and the muscle tissue recovers. With toxins, the body needs time to process the depositions of material leading to the blue discoloration, and it can take months for the skin to recover, especially if the exposure occurred over an extended period of time and was not treated early.