Why do people tan?

People have three pigments in their skin. This is what gives you your
color. There’s a yellow pigment, pink, and a brown pigment called
‘melanin’. Today we’ll be talking about melanin. If you have
dark skin, you have a lot of melanin, and if you’re light skinned, you
don’t. And, you guessed it, medium skinned people have a medium amount
of melanin.

When the UV radiation from the Sun hits your skin, it causes damage. So
your body reacts to prevent further damage. It produces more melanin.
Melanin absorbs the Sun’s radiation so it can’t enter your skin
cells and damage them. This increase in melanin is what causes a tan.

People with dark skin have more protection from the Sun. Their
ancestors came from places with a lot of bright sunlight, like the
tropics. But you need some sunlight to enter your skin. That’s how
your body makes Vitamin D. People with dark skin who live in bright
sunny places are fine. But if they live in colder, darker places, then
they need to make certain they get Vitamin D in their diet.

People with light skin absorb a lot of sunlight very quickly. Their
ancestors lived in places that were cold and darker than the tropics. We
often use the term “Caucasian” to describe these people. The Caucaus
Mountains are in Russia, which is cold and darker. So the people that
live there have light skin. When you spend most of the year covered up
in heavy, warm clothes, with only your face and hands exposed to
sunlight, you need light skin to absorb enough sunlight to produce
Vitamin D.

People who live in the areas in between the extreme north and the
tropics are in the middle. The temperature and the amount of sunlight
are both sort of medium. So people who have lived in these areas for
very long periods of time (I’m talking thousands of years) have medium
skin.