Causes of Melanonychia

Melanonychia often appears as a brown or black line running from the base of the nail towards its tip. It can affect one nail or several. Repeated pressure, a past injury, inflammation around the nail, or some medicines can activate pigment cells. Natural variation in pigment can also contribute, particularly when several nails show similar bands.

The pattern matters. A band that is new, widening, uneven in colour, or extending onto the skin near the nail deserves professional assessment. A clinician may inspect the nail with magnification and compare it with other nails before deciding whether monitoring or a sample is needed.

Take a clear photograph and note which nail is affected, when the change began, and whether the band is widening. Protect the nail from picking, biting, harsh chemicals, and repeated trauma. Do not try to scrape pigment away. If the cause remains uncertain, a dermatologist may discuss Nail Surgery to obtain tissue or treat a problem within the nail unit.

Book a dermatology review for a new band on one nail, especially when it changes, has several shades, becomes broader towards the nail base, or reaches the surrounding skin. Seek earlier care if the nail is painful, bleeding, lifting, or developing a growth. These signs do not prove a serious condition, but they should not be judged from appearance alone.

Ask whether the pattern fits pigment from trauma or another cause, whether photographs are enough for monitoring, and what change should trigger reassessment. Mention medicines, nail injury, family history, and any other discoloured nails.