The left and right side of my mouth is black this happened a few years ago I have used different lightening creams but it did not help. Can you help?

Dermatology. I think it is time then to see Dermatology. It is difficult to tell what is going on without actually seeing the discoloration. I think that if you have tried different remedies and no improvement then it is time to see a specialist for a better therapy. Best wishes.