Black toenail and melanoma: changes that need assessment

Colour alone cannot confirm the cause. A dermatologist assesses the pigment pattern, the surrounding skin, changes over time and any history of trauma. New, unexplained or evolving pigment should be examined rather than covered with polish or monitored indefinitely at home.

Nail melanoma may present with a brown or black band, irregular pigmentation, progressive widening, nail splitting, or colour extending from the nail onto the cuticle or adjacent skin. It may develop without pain. Not every dark band is melanoma, and people with darker skin tones can have harmless pigmented nail bands.

A bruise commonly follows impact or repetitive shoe pressure and usually advances towards the nail tip as the plate grows. Infection may produce thickening, crumbling or material beneath the nail. These clues can overlap, which is why an in-person nail examination matters when the explanation is uncertain.

Arrange a dermatology appointment for a new unexplained stripe or patch, particularly when it is widening, becoming uneven, affecting one nail or reaching the nearby skin. Remove nail polish before the visit if practical, and bring dated photographs that show how the mark has changed.

The clinician may examine the nail with magnification and compare it with your other nails. If the appearance remains concerning, sampling tissue from the nail unit may be discussed. Do not scrape, bleach or puncture the area, because injury can obscure the pattern and create infection.

Request prompt review when pigment spreads beyond the nail, widens near its base, develops mixed colours or irregular borders, or accompanies unexplained nail destruction, a lump, bleeding or a sore that does not heal. Lack of pain should not delay assessment because a concerning nail lesion may cause no discomfort.

A sudden dark nail after a strong impact may still require urgent care when pain is intense, the toe is deformed, sensation is reduced or bleeding continues. Redness that expands, increasing warmth, pus or fever points to possible infection and needs timely medical attention regardless of the pigment's cause.

Ask which features favour bruising, benign pigmentation, infection or a growth; whether magnified examination is sufficient; and whether a biopsy is advisable. If tissue sampling is proposed, ask which part of the nail unit will be sampled, how the toe will be protected afterwards and when results will be discussed.