This is a premalignant condition of the lower lip vermilion itself, whereas lip-licker's dermatitis is an irritant reaction on the perioral skin surrounding the lips.
This is inflammation specifically at the corners of the mouth, not the broader area around the lips affected by tongue contact.
Allergic contact dermatitis would be in a pattern matching the allergen (e.g., lipstick, toothpaste), not the characteristic distribution of where the tongue can reach.
