Well, in my case it started on the upper lip 11 years ago after I have bitten my upper lip. (I was 17) The condition rapidly spreads to the whole upper lip (including the corner) and then, after 5 years (and maybe after an un-appropriate cortison cream use) it goes to the bottom lip as well.
I'm currently using an hydrating cream because I think it's always better than letting the crust dry . So I can manage going to work, but it's not easy everyday, I admit.