Why has the area around the corners of my mouth become dark?

Question
The area around the corners of my mouth and near my chin have become noticeably darker. It does not wash off. Is it because of the sun or some hormonal thing? What can I do to make my complexion even again?
Expert Answer
B
Peri-oral pigmentation may be hereditary. Lightening agents (hydroquinone/kojic acid) in combination with tretinoin creams would help.