Why the area is getting hyper-pigmented? In my buccal mucosa it started now its spreading all over the labial mucosa, when i lick it it feels sour as if any wound is there, but no burning or itching. Why is that happening? Do i require a biopsy? I observed topical costicosteroids do work but aggravate it when stopped.. Help. Non smoker, no tobacco usage, occasional alcohol user(very rare). I can eat spicy food without issues.