Your Guide to Sunscreen Protection: STACK Summer Workout - Exercises, Training, Nutrition, High School Athletes

Use this guide to protect yourself from the harsh summer sun when you take your game outside.

SPF stands for Sun Protection Factor. The SPF of a particular sunscreen is a measure of its effectiveness. The higher the SPF, the more protection it provides against UV-B, the ultraviolet radiation that causes sunburn.

If the bottle doesn’t say it, the sunscreen isn’t waterproof or sweatproof. So if you’re so sweaty it looks like you took a dip, reapply—even if it hasn’t has been as long as the SPF should allow.

Sunscreen absorbs the sunlight safely, while sunblock reflects it away from the skin. Sunblocks are messy and can stain clothes. Use them on highly sensitive areas like your nose, lips, ears and shoulders.

The higher the SPF, the longer and more powerful the protection. Picking the proper SPF depends on your skin type and how it reacts to sunlight. However, you can understand SPF this way: wearing an SPF 50 means your skin will not burn until it has been exposed to 50 times the amount of UV radiation that would normally cause it to burn.

Reapplying depends on the SPF. Use the formula above to calculate how long you can go without reapplying. And if you lose track of the last time you put it on, apply at least every two hours.