DARK LIPS
Some people develop darker lips over time due to a range of medical hyperpigmentation, a harmless condition caused by an excess of melanin.
Lips hyperpigmetation may be caused by:
--Excessive exposure to the sun.
--Lack of hydration.
--Cigarette smoking.
--Allergic reactions to toothpaste, lipstick, etc.
--Too much caffeine.
--Lip sucking.
There are various treatment for lightening dark lips, however, you might consider a natural lip lightener......LEMON