What does sun protection factor (SPF) mean?
The sun protection factor extends the time it takes for the skin to turn red by a factor of X. A person who burns after 10 minutes of sun exposure without sunscreen would not get sunburn for 100 minutes using a sunscreen with a sun protection factor of 10. However, even before visible skin damage or sunburn can occur, it’s the best not to stay out in the sun any more than up to 60% of this time.
