Question: Why does the sun lighten our hair, but darken our skin?

Rebecca Shaw answered on 11 Nov 2019:

Melanin is a pigment which we have in our skin and hair that gives it colour. When you are in the sun, you are exposed to energy it produces called UV rays. UV rays can be damaging and so the body produces melanin to absorb and protect you from them.

In the skin, if exposed a lot to UV rays, cells will produce more melanin to absorb them and that produces a darker skin colour. So when you get a sunburn, you do not have enough of this protecting pigment and you are damaging your cells which produces the red colour. That’s also why we peel because our skin cells have been damaged.

Our hair is another story. Our hair is not technically alive (atleast the part that has grown out of our hair follicle isn’t) and so once exposed to UV rays, it cannot make melanin to absorb them. Instead they get bleached and this makes your hair appear lighter!