What should you know about dark stripes on nails?

Dark stripes on nails can have several causes, so a new or changing stripe should be examined rather than treated based on appearance alone. A clinician may look at the stripe, the surrounding skin, and other nails, then decide whether monitoring or testing is appropriate.

A stripe may reflect pigment produced in the nail, a mark left after trauma, or material beneath a thickened nail. Nail fungus can cause discoloration and thickening, while nail psoriasis can create surface changes and altered color. A single narrow band, a broadening band, pigment extending onto nearby skin, or a stripe that appears without a clear injury deserves closer attention. The appearance alone cannot identify the cause.

Take a clear photograph in good light and note when the stripe appeared, whether it is changing, and whether the nail is painful or lifting. Avoid scraping, drilling, or covering the nail until it has been assessed. Keep nails trimmed without cutting into the surrounding skin, and mention medicines, recent injuries, salon treatments, or repeated pressure to the toe or finger. If infection is suspected, treatment may require confirmation before an oral antifungal treatment is considered.

Arrange a dermatology assessment promptly for a stripe that is new, widening, uneven, changing in color, or associated with pigment on the skin beside the nail. Seek earlier care if the nail bleeds, becomes tender without an injury, separates, or develops a persistent lump. Sudden severe pain, marked swelling, or spreading redness warrants urgent medical attention.

Ask what features support the suspected cause, whether the stripe should be photographed and monitored, and whether the nail needs a closer examination or a sample. You can also ask how to protect the nail while waiting and what change should trigger a faster review.