Alien: what is that human rubbing into their skin?

Human: Oh thats sunblock. it helps protect our skin from the radiation of the sun since it can damage us and give us cancer if exposed long enough

Alien: That makes sense. And what is that human slathering onto their skin?

Human: Oh that is tanning lotion. it intensifies the radiation of the sun to make our skin damage faster so we can look aesthetically pleasing.

Alien: I give up trying to understand your planet