Hello, I am a non-smoker. Recently, part of my bottom lip has changed from its original pink color to black, forming a long dark mark across the middle of it. Today, I've noticed a small fissure right in the middle of the lip when I opened my mouth wide trying to eat. I also feel a burning sensation when I lick my lip. But since it started, I haven't necessarily licked my lips more than usual, and licking my lips was never an issue in terms of dehydration.