Hi Dear,
Welcome to Health Care Magic Team.
Understanding your concern.
black line on lower lip as per your query could be because of
hyperpigmentation ,
allergic reaction to certain chemical agents such as dyes , cosmetic products , side effects of any medication and could be because of
melanin deposition due to excessive exposure to UV rays of sun.
It can also caused by dryness of lips. Because of skin irritation you must do excessive lip licking can cause
chapped lips.
Do not lick or pick your lips . I would suggest you to do not let them dry . Apply natural lip balm on lips to prevent from drying , apply kojivit cream at night and do not apply with finger as again and again that will cause infection , apply directly. Use tea tree oil dipped in cotton swab for fastening the healing and prevent discoloration. Avoid excessive exposure to sunlight.
You will get relief in 1-2 weeks, if your condition keeps on persisting visit
dermatologist once. Doctor may recommend chemical peeling like procedure
Hope your concern has been resolved.
Get Well Soon.
Best Wishes,
Dr. Harry Maheshwari