Urine rubbing - Absorption

How does the nutrients of my urine I rub on my body get into my body-sytem, e.g into my muscles?

I don't understand the route of this. Can nutrients enter the body via the skin?

If nutrients can enter the human body through the skin, so why do we use e.g sunscreen, this could be harmful?

Whats the excactly advantage of external urine rubbing?

Hope-2008