The optics of the lip
Because the keratin layer over the vermilion is so thin and clear, and there is little melanin to speak of, light passes in, bounces off the dense capillary bed and comes back carrying the red of oxygenated haemoglobin. That is why healthy lips are pink-red and why the same lips go pale when you are cold, frightened or unwell.
What dulls lip colour
Ageing thickens and dries the surface and reduces blood flow; sun damage does the same; smoking constricts vessels; anaemia lowers haemoglobin; and simple genetics give some people a naturally low-contrast lip. Cosmetic vasoconstrictors used during the procedure temporarily blanch the lip, which is why the colour looks weak mid-session.
How blushing compensates
Implanted warm pigment adds back the red-pink that failing blood supply no longer provides, and does it consistently regardless of temperature or health. It is, in effect, a permanent stand-in for a good circulation flush.
