Most of us think of the Sun as our friend. It helps plants grow, keeps us warm, and who doesn't love to lie on the beach on a sunny day?
But for all of it's good qualities, the Sun can also be harmful in large amounts. That's why we invented sunscreen.
The purpose of sunscreen is to shield the body from the Sun's ultraviolet rays, which have several harmful effects, including sunburn, aging, and skin cancer promotion.
These rays are separated by their different wave lengths, into types such as UVA and UVB, which exert a variety of effects in the skin due to the absorption patterns of chromophores, the parts of the molecules responsible for their color.
The primary two chromophores are hemoglobin, found in our red blood cells, and melanin, which gives our skin its pigment.
We know that UVB rays cause the skin to burn. The role of UVA rays is less well understood and appears to have an effect on our tanning response, carcinogenesis, and aging.
So, how does the sunscreen protect us from these rays?
There are two basic types of sunscreen, physical and chemical blockers.
Physical blockers, like zinc oxide or titanium dioxide, reflect the Sun's rays by acting as a physical barrier.
If you've seen lifeguards with noses covered in white, then you know what this looks like.
