Q: Why does the sun lighten our hair, but darken our skin?
A: This is an interesting question and to answer it, you should think about the nature of skin, versus the nature of hair. The two have many similarities, but are different in some key ways. Specifically, skin is
comprised of layers of cells of living tissue, while the hair is made of keratinized (hardened) protein and is dead tissue.
When skin is exposed to the sun, the sunís radiation stimulates the skinís melanocytes to produce melanin, which is meant to protect the skin from damage caused by the sun. People
naturally have differing amounts of melanin in their skin and the melanin gives us the whole range of skin tones and colors. Usually, those with more melanin are less affected by the sunís rays (at least in that they
are less likely to get sunburn). And the fact that the melanocytes in the skin produce additional melanin when exposed to the sunís rays is why some people grow tan from being in the sunshine.
When the hair is exposed to the sun, the sunís radiation breaks up the pigment molecules in the hair which results in a lightening of the color (or in some cases a fading of more
vibrant artificial colors). The hair lacks the means to protect itself from sun damage naturally, which is why there are products made for use in the sun to protect the hair.