What should you know about melanonychia on multiple nails?

The pattern across several nails can provide useful clues, but it does not identify the cause by itself. A clinician may examine the nails, surrounding skin, hands and feet, and review your medicines and health history.

Melanin is the pigment that gives skin, hair and nails their colour. When pigment-producing cells in the nail area become more active, a narrow or broad brown-to-black band can show through the nail. Several nails may be involved after repeated pressure, picking, manicures, or other minor injury.

Multiple bands may also occur with changes in skin pigmentation, inflammatory nail or skin conditions, some medicines, or infection. The colour, number of nails, shape of each band, speed of change, and whether the surrounding skin is also darker all matter. A photograph from above, taken in good light, can help track change over time.

Arrange a routine dermatology assessment if the bands are new, unexplained, or continuing to change. Bring a list of medicines and supplements, mention recent nail trauma or cosmetic treatments, and describe when you first noticed the pigment. Do not scrape, file, or repeatedly cover the bands while waiting, because irritation can obscure the nail surface.

A clinician may use magnification to inspect the pigment pattern. If one nail looks different from the others or the diagnosis remains uncertain, further testing may be discussed. Treatment is directed at the cause; a harmless pigment pattern may only need observation.

Seek prompt medical review for a band that is rapidly changing, becoming wider or more uneven, or extending onto the skin beside the nail. Also arrange an earlier assessment for bleeding, persistent pain, swelling, nail lifting, or a new dark mark limited to one nail. These features do not establish a serious diagnosis, but they should not be assessed from photographs alone.

If several nails changed suddenly after starting a medicine or during a significant illness, contact the clinician who manages that treatment or condition. Do not stop a prescribed medicine without advice.

Ask: Does the pattern across my nails suggest one likely cause? Could trauma, a medicine, infection, or a skin condition explain it? Does any band need closer examination or testing? What changes should I photograph and report, and when should the nails be reviewed again?