What should you know about black marks on toenails?

Blood trapped beneath the nail may look red-purple at first and then brown or black. Pigment, infection, medication effects, and a growth beneath the nail can also alter colour, so the shape and movement of the mark matter.

A bruised nail can present after stubbing the toe, sport, or repeated pressure from tight footwear. The dark patch sits beneath the nail plate and should gradually move toward the tip as a new nail grows from the base. It may be tender soon after injury.

A brown or black lengthwise band may be normal pigment, especially when similar stable bands affect several nails. However, nail melanoma can present as a new or widening dark band, pigment spreading onto nearby skin, nail splitting, lifting, or a bump. It may cause no pain.

Remove nail polish and photograph the whole nail, its base, and surrounding skin in clear light. Record any injury, shoe pressure, medicine changes, and whether other nails have similar marks. Watch whether an apparent bruise advances toward the free edge rather than remaining fixed at the base.

Wear roomy shoes, keep the nail trimmed straight across, and avoid drilling or piercing it yourself. A clinician may release fresh trapped blood when pressure pain is severe and the injury is suitable. Nail surgery or a biopsy is reserved for findings that require drainage, diagnosis, or removal.

Arrange prompt dermatology review for a new dark band without a clear injury, a mark that widens or has irregular colours, pigment on the cuticle or nearby skin, nail splitting or lifting, a lump, bleeding, or a spot that stays near the nail base as the nail grows.

Seek urgent care after a major toe injury if pain is intense, the toe looks bent, bleeding will not stop, or walking is difficult. Fever, pus, spreading redness, or increasing warmth can indicate infection and also warrants timely medical care.

Ask whether the colour is in the nail plate, under it, or in the nail-producing tissue; whether its pattern fits blood or pigment; and whether photographs are enough to monitor it. If a biopsy is proposed, ask which part will be sampled, how the nail will be protected, and what recovery involves.