Q: What is SPF?
A: The #SPF (sun protection factor) number indicates how long the sun’s UV radiation would take to cause a sunburn when using the product exactly as directed compare to the amount of time without any sunscreen. So ideally, with SPF 50 it would take you 50 times longer to burn than if you weren’t wearing sunscreen.
SPF only measures protection from UVB radiation. It has nothing to do with deep-penetrating UVA radiation. A product with SPF can protect you from sunburns, but it could still leave you vulnerable to doses of UVA radiation.
Regardless of the SPF, it’s important to apply one ounce (two tablespoons
) 30 minutes before going outside and reapply it every two hours or immediately after swimming 
or sweating 
.
