Blue Bloods
Another cause of blue skin hues can be a lack of oxygen in the blood, tinting the blood so that the flesh it circulates in has a blue hue. This is just as unhealthy as it sounds... but first, a small digression from topic.
The phrase “Blue Blood” is used to designate a person of royal heritage in many European countries. A popularly repeated theory is that this phrase describes a condition caused by a rare genetic defect that is carried by the royal families of Europe, due to their habit of only ever marrying other members of European royal families. This small breeding pool is said to have led to a tendency for the disease called “hemophilia” to be inherited by royals, and it is believed by some that this condition is the origin of the phrase “Blue Blood”.
There actually is a genetic propensity for hemophilia in some members of the European royal families, spread by the “Granmama of Europe,” Queen Victoria [1819-1901]. She earned this name because she had a large number of her children and grandchildren marry into royal houses all across Europe... but this also spread her genetic propensity for hemophilia, which most often appears in males with the gene. The gene seems to have developed in the queen as a fluke mutation.
However, the hemophilia explanation for the phrase “Blue Blood” has a major flaw: hemophilia doesn’t turn blood blue, nor give a bluish tinge to the skin. It simply means the body is missing some of the agents in the blood that help it to clot when vessels are broken, so sufferers bleed longer before clotting takes place. Depending on the type of hemophilia, the victim’s blood may clot so slowly as to be equivalent to not clotting at all. Queen Victoria’s son Leopold died in 1884 after a fall that would have given a normal person a mere bump on the head; but because of his hemophilia, he was dead within a few hours due to a massive brain hemorrhage.
The actual origin of the term “Blue Blood” for royalty comes from the Spanish phrase “Sangre Azul” (literally “blue blood”), used to describe the fact that when the Spanish were conquering lands held by the Moors, the Spanish nobility displayed the fact that they had white, untanned skin, through which blue veins were easily seen, as proof that they were not related to the darker skinned Moors.
A further myth that needs to be dispelled is the idea that blood can actually be colored blue to start with... it can’t. Blood has a limited range of color from a bright red to a dark maroon, mostly depending on the levels of oxygen being carried by the hemoglobin in the red blood cells. Because the red blood cells are the predominant type of cell in the blood, well beyond the white blood cells that fight bacteria and the platelets that help close wounds, the overall color of blood is red.
Veins appear to be blue for two reasons. First, of course, they are carrying the de-oxygenated blood, colored the darker maroon, back to the heart to be cycled through the lungs. Secondly, due to the properties of the skin itself, the light reflecting back from the veins within the flesh has the red range of the light spectrum absorbed, leaving only a blue wavelength... making the veins look blue.
Arteries run deep within the body to carry the oxygenated (and redder) blood throughout, while the veins cycle the de-oxygenated blood (more maroon) back to the heart near the surface of the body; this makes the veins more visible. Since the flesh of the body cancels out red color wavelengths of light passing through it, flesh color is usually determined by the melanin in the skin which is the most visible coloring agent, with some visibility of the bluer veins near the surface.
If de-oxygenated blood cells (with the maroon color) start to flow in the arteries as well as in the veins, the blue color from light reflecting off the maroon blood cells in the arteries becomes visible, giving the skin an overall bluish tint. This doesn’t require a great amount of the de-oxygenated blood, simply because the color of the oxygenated blood doesn’t effect skin tone at all... the light that would display the red color of the oxygenated blood cells is absorbed by the flesh of the body, so only the maroon blood, however much or little there may be, is visible through the skin.
Luckily, de-oxygenated blood doesn’t normally circulate through the arteries; the job of the arteries, after all, is largely to get oxygen to all the parts of the human body, so the less oxygen it carries, the greater the danger to health. But this situation does happen from time to time — the condition is called cyanosis, and there are a variety of causes — and unlike the indigo dye myth above, this condition actually causes blue babies to be born.