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What is an undertone, really? The biology of skin color
Three pigments shape your skin color. Here is what they do, and why the vein test is only a rough guide.
"Warm" and "cool" undertones are the foundation of seasonal analysis, but what are they physically? The answer lies in a few pigments and in how light travels through skin.
Three ingredients
- Melanin sets most of your skin's depth. It comes in a brown-black form and a red-yellow form, and tanning increases it.
- Hemoglobin in the blood near the surface adds red. Oxygen-rich blood is brighter red than oxygen-poor blood.
- Carotenoids, yellow-orange pigments from fruit and vegetables, are deposited in the skin and add yellowness.
Diet really does show. Research from the University of St Andrews found that people who eat more fruit and vegetables have yellower skin, and that changes in intake shift skin yellowness and redness within about six weeks.
So what is an undertone?
In color analysis, undertone describes the balance between golden-yellow and pink-red in your skin, separate from how light or dark it is. Two people can have the same depth of skin but opposite undertones. Because undertone is about balance rather than depth, it tends to stay recognizable whether you are pale in winter or tanned in summer.
The trouble with the vein test
You've probably been told to check whether your wrist veins look blue or green. The blood in your veins is dark red, never blue. A 1996 study in Applied Optics showed that veins look bluish because of how skin scatters and absorbs different wavelengths of light, how deep and wide the vein is, how oxygenated the blood is, and how our brains interpret contrast with the surrounding skin.
That means vein color is shaped by your skin's optics and your vein depth, not only by undertone. It can still be a useful clue, but it isn't a measurement. That's why good at-home analysis combines several checks: veins, gold versus silver, and bright white versus cream.
Check yours
Our Find My Season tool combines a photo reading of your skin with those classic checks, and warns you when they disagree.
Sources
- Kienle, A. et al. (1996). Why do veins appear blue? A new look at an old question. Applied Optics 35, 1151–1160.
- Stephen, I. D. et al. (2009). Facial skin coloration affects perceived health of human faces. PubMed.
- Stephen, I. D., Coetzee, V. & Perrett, D. I. (2011). Carotenoid and melanin pigment coloration affect perceived human health. Evolution and Human Behavior.