(Concern) Are there anyone with severe pigmentation?

Are there any people with severe pigmentation?

My skin isn't particularly sensitive or prone to skin conditions; it's just slightly tan, but I feel like I have especially severe pigmentation.

Especially, the elbow is the most severe, making it difficult to wear short sleeves, and I am worried because it seems to be spreading gradually.

Next is the knee and then the mouth, and when a friend asked me why my mouth was so dark, I really wanted to crawl into a hole.

I'm worried because pigmentation is occurring in the overlapping areas of the skin, and I don't know if applying ointments or similar treatments would be effective. Would procedures like that be helpful?