How does sunscreen prevent sunburns?

Sunscreen. Sunscreens work via 2 possible ways: 1) chemical blocks that breakdown the uv rays as they pass through the skin and 2) physical blocks that prevent the uv rays from getting to the skin. I recommend the physical blocks (zinc and titanium) because they have a very good safety profile and work very effectively. If you are going to be in the sun - use a minimum of spf 15 - follow product directions.
It's a barier. Sunscreens are a barier to the harmful ultraviolet rays of the sun. You are less likely to get burned in the shade, but if you are in the sun, sunscreen helps to protect your skin. It is very important to reapply sunscreen frequently, and especially after swimming, as it is continuously being worn off.

Related Questions

In what ways does sunscreen slow down and prevent sunburns? |

Sunscreen. Sunscreens help prevent sunburn by slowing down the rate of absorbtion of ultraviolet rays by the skin. For example a number 15 sunblocker applied to the skin will cause the skin to absorb only 1/15 of the suns rays as opposed to unprotected skin. In other words, protected skin with sunblocker would take 15 hours to absorb the same amount of radiation absorbed in one hour by unprotected skin. Read more...
Blocks radiation. Sunblock or sunscreen will interfere with penetration of harmful ultraviolet radiation which has the potential to cause genetic mutations that may lead to skin cancer. Read more...