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Differing
skin colors are due to the presence of the colored components
of the skin in different proportions.
contribution of blood to the complexion color is most obvious in
the cheeks, where capillaries are most numerous and closest to the
surface.
Apparent skin color can change if the combination
of its colored components changes. Changes like these are more
obvious if very little melanin is present, since melanin can hide
most of the other colors. This is why people with very pale skins
- 'porcelain' skins -can look blue if they get cold: blood that
moves sluggishly carries less oxygen, and so looks bluish rather
than having the bright red color that is given by full oxygenation.
Pigmentation disorders
There are some rare congenital pigmentary disorders of skin. In
one, the pigment is spread
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out along the otherwise invisible lines on the skin called Blaschko's
lines.
Vitiligo is a condition where there is patchy
loss of pigment, usually over the hands and forearms but occasionally
it is more extensive. It is possible to hide it by the skilful use
of special water-resistant cosmetics.
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