Bought any sunscreen lately? Did you choose based on the SPF or the UVA rating? Or the UVB? Do you have a clue? I didn’t, so I looked it up. Here’s the scoop.
There are two types of ultraviolet light we need to filter out. UVA is the type that causes skin aging and skin cancer. It’s sneaky–it doesn’t feel like it’s burning you, but it’s penetrating deep, causing more damage.
The other type is UVB. It’s the painful one that literally burns the topmost layers of skin.
SPF (Sun Protection Factor) tells us how much UVB light is being filtered out. The marketing purpose of the SPF number is to tell us how long we can stay out in the sun before we burn. For instance, SPF-30 means we can stay out 30 times longer than if we had no sunscreen on. Not 30 minutes…30 times, which is a meaningless number, since most of us don’t know how long we can stay out with no sunscreen in the first place. Furthermore, the SPF factor only protects against the burning kind of UV, not the cancer-causing kind.
So instead of trying to parse it all out, just go with what dermatologists recommend: Use a broad spectrum UVA/UVB sunscreen to protect against both types of ultraviolet light. Reapply it every 2 hours.
From Fastnewleters August 2021