❓ why
Why do veins look blue under the skin?
human-bodyscience
Quick Answer
Veins are not actually blue; the skin absorbs red light and reflects blue light more from deeper tissues, making veins appear blue or green.
The Full Story
Blood is always red: bright red when oxygenated in arteries and darker red when deoxygenated in veins. The blue appearance is an optical illusion caused by how light interacts with skin. Red light penetrates deeper and is absorbed by the blood, while blue light is reflected back from the skin and surrounding tissue above the vein. The brain interprets this contrast as a blue colour. The effect is strongest in fair-skinned people and in veins close to the surface. Arteries run deeper and are not usually visible.
Key Facts
1.Deoxygenated blood is dark red, not blue.
2.Red light penetrates skin more deeply than blue light.
3.The blue appearance is stronger in lighter skin.
YouTube Angle
Suggested video title for this topic:
"The vein colour myth — why your blood is never blue"