Snapshot · Stuff You Should Know
Deoxygenated blood is not actually blue — veins appear blue because blue light cannot penetrate as deeply as red light, so blue light is reflected back to the eye.
Where this was said
At 17:50 · chapter starts 16:00
Chuck and Josh tackle hemangiomas, the raised reddish 'strawberry marks' that alarm new parents but are usually benign. Only about 30% are visible at birth; most appear between 4–6 weeks and are gone by the time a child reaches double digits. Large ones near the eyes or ears can pose medical risks, and hemangiomas can extend internally to organs in rare cases. The discussion of why deeper hemangiomas look blue rather than red triggers a wonderfully entertaining detour: the hosts debunk the playground myth that deoxygenated blood is blue [1] — Josh Clark "Blood is never blue — not even when deoxygenated. Veins appear blue because blue light can't penetrate as deeply as red light, so it reflec…" 17:20 . Josh explains the actual physics — blue light reflects off shallow tissue while red light penetrates deeper and is absorbed — a fact Chuck swears he didn't know until that very morning.
Blood is never blue — not even when deoxygenated. Veins appear blue because blue light can't penetrate as deeply as red light, so it reflects back to the surface. Red light goes deeper and gets absorbed, making deep tissue appear blue to the eye.
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