By Nellie Day
Before we determine how a sunscreen's properties are effective at protecting your skin, we need to know what they're protecting the skin from. Natural sunlight contains three types of ultraviolet radiation, UV-A, UV-B and UV-C. Though UV-C is not absorbed by the skin, UV-A and UV-B are. UV-A has more harmful effects on the skin, such as breaking down the skin's elasticity or causing...