Why Does Our Skin Darken in the Sun, While Our Hair Lightens in the Sun?
This is a great question. While it may seem odd that the sun bleaches our hair while darkening our skin, it is not so hard to understand when we remember that hair is dead, but skin is alive. Hair is a growth of dead skin cells, so there is no living substance in hair (though it may look shiny and healthy).
Melanin is a pigment found in your skin and hair cells that gives skin and hair their color. If you spend a lot of time outside in the sun, it might destroy a lot of the melanin in your hair, making your hair lighter. And, since the hair is dead, your hair will remain that color until you grow some new hair.
The sun also destroys the melanin in your skin, but since your skin is alive, it can respond to the sun’s damage. Your skin cells make more melanin, which protects our skin by filtering out potentially harmful ultraviolet (UV) radiation from the sun’s rays. UV light can cause skin cancer, so the protective melanin is very important.
When the sun damages a skin cell, the cell releases chemicals to let the body know that it has been damaged. These chemicals cause more melanin to be made. However, hair is left with no protection and has to take the full force of the sun’s beating.
Isn’t it wonderful that God has made our bodies so that they protect themselves from the sun (which He also created)? Evolution cannot explain the spectacular design of the human body.