Hmm. Does it stay on well? I suppose there's no way to determine its effectiveness over time without some kind of research.

The Chapstick brand lip balm that I use is SPF 30 and seems to stay on reasonably well. It also prevents chapping which can be a pain in the neck to deal with. Again, though, I have no research available to me that indicates how long the sunscreen component remains functioning. I reapply frequently.

Good idea to use sunscreen if you forget/lose the chapstick.

HJ