Hello,
It can be due to hyperpigmentation
lips. To prevent blackness of the
lips,
smoking and chewing, biting or pricking the skin of the lips should be avoided. The most effective solution for treating dark lips is alexandrite and ND-Yag Q-Switched laser treatment. Please discuss these options with your dermatologist.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided.