How Does Sunscreen Work?

Broad-spectrum sunscreen works by blocking UVA and UVB rays from penetrating the skin. Sunscreens that come with an SPF of 15 or more are highly effective at protecting one's skin from the sun's rays.

The sun produces two types of rays that are harmful to the skin: UVA and UVB. While UVB causes sunburn, UVA moves deeper into the skin and increases the risk of premature wrinkling. Sunscreen with an SPF of 15 makes the skin take 15 times longer to burn. If someone usually burns after 20 minutes, an SPF 15 cream should increase that time to 5 hours. Sunscreen users should reapply their product every two hours to reap the maximum benefits.

The higher the sunscreen's SPF, the better it is at preventing sunburn. SPF 15 sunscreens block 93 percent of UVB rays, whereas SPF 30 sunscreens block 97 percent. It is important to recognize that a UVB sunscreen does not protect the skin against UVA rays. As such, there may be unseen damage even if there is no reddening present.

Broad-spectrum sunscreens block UVB and UVA rays using a combination of organic and inorganic substances. For example, oxybenzone absorbs UV radiation and dissipates the heat that causes burning. People can purchase sunscreen in spray, lotion and wax form. Individuals who are going to spend time in the water need to choose a water-resistant sunscreen.