Melanonychia and nail biting: what to know

Biting and picking can repeatedly traumatise the nail plate, cuticle and skin beneath it. This may cause tenderness, ridges, small areas of bleeding or pigment changes as the nail grows. Bacteria can enter damaged skin, leading to inflammation around the nail.

Trauma is only one possible explanation for melanonychia. A band that remains in one nail, widens, becomes uneven or reaches the surrounding skin should be examined rather than labelled as a biting injury. The timing of the mark and its movement with nail growth are useful clues.

Keep nails short with a smooth file, moisturise the cuticles and cover broken skin with a clean dressing. Notice when biting occurs, such as during stress or concentration, and use a replacement habit like holding a small object. Avoid cutting or pushing back the cuticle while the area is irritated.

Photograph the nail regularly in consistent light and record whether the band moves toward the tip. If stopping the behaviour is difficult, a clinician or therapist can help identify triggers and build a gradual plan. Do not scrape or dig beneath the nail to remove pigment.

Seek dermatology advice for a persistent or changing band, pigment extending onto nearby skin, or a mark that appears without a clear injury. Get prompt help for increasing pain, warmth, swelling, pus, fever, bleeding or nail separation.

Ask whether the appearance fits trauma, infection or another nail condition, and whether photographs are enough for monitoring. If the band is concerning, ask whether nail surgery or sampling is needed and how to protect the nail afterward.