Hyperpigmentation. Hyperpigmentation (or darkened skin) is caused by a variety of things. Here are a few common causes: 1) ultraviolet sunlight 2) hormones in the body (can be related to pregnancy - melasma) 3) post-inflammation from any number of causes (hair plucking, acne, trauma, harsh skin care products or laser treatments) treatment may include time, skin lighteners, ipl laser, sun protection. Hope this helps.
Melasma. Genetics, sunlight and estrogen can cause hyperpigmentation of the lips.