Understanding SPF Protection
SPF (Sun Protection Factor) measures how long sunscreen protects against UVB radiation compared to unprotected skin. SPF 30 means you can stay in the sun 30 times longer before burning. However, real-world protection depends on proper application (1 oz for full body), reapplication every 2 hours, and factors like sweating, swimming, and altitude. Higher altitudes increase UV exposure by about 10% per 1,000 meters.