What kind of procedure can improve pigmentation around the mouth?

Are there any of you with dark spots on both corners of your mouth?

Sometimes when I look in the mirror, I get startled wondering if there is something on it.

I think it is harder to look like a very unhygienic person than to have it interfere with my daily life.

I found that rubbing it in with concealer before applying makeup didn't improve it; instead, it made the makeup look thicker and messier, so it had the opposite effect.

What kind of procedure would improve the pigmentation around the mouth?

If you know of any effective procedures that aren't very painful, please share the information.