Causes of longitudinal melanonychia

The band may be tan, brown, or black and can affect one nail or several. Repeated injury, nail biting, picking, or pressure can stimulate pigment. Inflammation, infection, and some medicines can also alter nail colour. A clinician looks at the band’s width, colour pattern, borders, location, and whether it begins in the nail fold or changes as the nail grows. Skin tone and age are relevant context, but they do not replace an examination.

A line that moves outward with nail growth may behave differently from pigment that widens or changes near the nail base. A photograph can help document progression, but it cannot establish the cause.

Do not scrape, file, or cover the band while trying to remove it. Protect the nail from pressure and note when you first saw the change, whether an injury preceded it, and whether other nails are involved. Bring a medicine list and clear photographs. A dermatologist may monitor the nail or recommend nail surgery when direct sampling is needed; the choice depends on the examination.

Arrange a dermatology assessment for a new band on one nail, a line that is widening or becoming uneven, pigment extending onto nearby skin, nail splitting, bleeding, pain, or a persistent change without a clear injury. Prompt review helps distinguish harmless pigment from conditions needing treatment.

Ask what features make the band reassuring or concerning, whether monitoring is suitable, how often it should be photographed or reviewed, and what nail surgery would involve if sampling is advised. Mention trauma, nail habits, medicines, and changes in other nails.