Maybe you've heard that blood is blue in our veins because when headed back to the lungs, it lacks oxygen. But this is wrong; human blood is never blue. The bluish color of veins is only an optical illusion. Blue light does not penetrate as far into tissue as red light.
Blood does change color somewhat as oxygen is absorbed and replenished. But it doesn't change from red to blue. It changes from red to dark red. It is true that veins, which are sometimes visible through the skin, may look bluish.
Blood is red, and a surgeon will tell you our veins too are red, they only look blue when we see them through our skin. But why? The answer depends on a number of things, including how your eyes perceive colour, how light behaves when it contacts your body, and the special properties of blood.
Now you remember that deoxygenated haemoglobin in veins was a darker shade of red than oxygenated haemoglobin in arteries. This rather small difference is amplified as the light travels through the skin, and the overall result is that in comparing arteries and veins, the veins will look more blue.
The blue and purple hue of the veins stems from the way light is refracted on the skin. Because the veins may be located at slightly different depths under the skin's surface, the color of the veins may be somewhat different in different areas.
Spider veins are damaged blood vessels just under your skin that look red, blue or purple. They're usually harmless. Spider veins don't typically cause any symptoms, but rarely, may cause burning, itching or discomfort (especially in your legs).
Spider veins, which may surround varicose veins, are smaller red or purple lines that appear close to your skin's surface. Although they can be unsightly and uncomfortable, varicose veins aren't dangerous for most people. In some cases, severe varicose veins can lead to serious health problems, such as blood clots.
Reasons That Veins Are Blue
The primary reason veins are blue is the way wavelengths of light hit the skin. White light can carry colors and waves with varying lengths. Red has the ability to travel the farthest. Violet waves are the shortest, and all the other colors fall somewhere in between.
Blue or dark-colored veins are normal and healthy, although it can be a bit strange seeing sudden prominent blue veins pop up on your skin. Veins can become more visible due to various reasons, including decreased body fat, aging, genetics, physical activity, pregnancy, sun exposure, and certain medical conditions.
The veins themselves are not blue, but are mostly colorless.
It is a common myth that veins are blue because they carry deoxygenated blood. Blood in the human body is red regardless of how oxygen-rich it is, but the shade of red may vary. The level or amount of oxygen in the blood determines the hue of red.
Bulging veins can occur due to: Temporarily rising blood pressure and/or body temperature. When you're exercising or working with your hands, blood flow in the area increases. Veins also swell in warmer conditions, as the body sends blood toward the surface of the skin to cool down.
Under darker skin, veins often appear green. And they can appear blue or purplish under lighter skin tones. That's because green and blue wavelengths of light are shorter than red wavelengths.
In most cases, there is no need to worry if your veins appear green because it usually indicates that blood vessels are working well. Green veins on the hand or legs are superficial veins that lie close to the surface of your skin.
The arteries (red) carry oxygen and nutrients away from your heart, to your body's tissues. The veins (blue) take oxygen-poor blood back to the heart. Arteries begin with the aorta, the large artery leaving the heart. They carry oxygen-rich blood away from the heart to all of the body's tissues.
Veins become dark and visible when there's a problem with their function. If problems arise with the vein valves, the blood itself or the surrounding muscles, blood may pool inside the veins instead of being transported back to the heart.
If you have pale skin it's not uncommon to see blue veins traveling across your arms, neck, chest and legs. In fact, visible veins that show through the skin's surface are just a part of life. But if you have big, blue, bulging veins you have varicose veins—and a red flag for vein health.
Veins themselves are typically fairly colorless. So don't panic if your veins look a little bit blue, that's not uncommon. If however, your veins or arteries suddenly begin bulging or turning a dark color, those may be warning signs of underlying health conditions.
The veins you can see through your skin look blue because of the way that your skin and veins absorb and reflect different wavelengths of light. While the shade of red may vary depending on how much oxygen your red blood cells are carrying, your blood is red, both outside and inside your body.
If you look closely at your body, you may notice the faint blue tint of your veins webbing through your arms, hands, and legs. Typically, this is barely visible, but due to age, lifestyle, and health, your veins may become more pronounced. If your veins are appearing more prominent, this may not be a reason to panic.
When these valves weaken, some blood flows backward and accumulates in the vein. Extra blood in the vein puts pressure on the walls of the vein. With continual pressure, the vein walls weaken and bulge. In time, we see a varicose or spider vein.
The blood going out to your body in the arteries is full of oxygen, which makes the blood bright red. But the blood coming back from your body in the veins is darker because your body parts have used up the oxygen in the blood. That's why veins look purple or blue.
Stress may cause spider veins to develop by increasing blood flow through your body's smaller blood vessels. The extra pressure from the increased volume of blood passing through these tiny capillaries causes them to stretch and become damaged over time.