I think mine started from constant use of Carmex. I used it 3-4 times a day and even smoked cigs and pot with it on. I would then wipe off the slime and reapply, not knowing what the slime was at the time.
Then I decided to quit smoking and stop using Carmex and I let my lips do their own thing. This resulted in my lips drying and crusting really really bad. Then stupidly I picked and peeled huge chunks of the dry skin off and here I am today 2 years later.