What should you know about horizontal melanonychia?

Melanonychia occurs when pigment is produced or deposited in the nail unit. A horizontal band differs from the more familiar lengthwise band and may follow a temporary change in nail growth, local irritation, inflammation, medication exposure, or pigment activity. A single nail, several nails, the colour, and the band’s edges all provide useful context.

A dark nail mark is a symptom, not a diagnosis. A clinician compares it with your skin and other nails and asks about injury, illness, medicines, and how it has changed. General information about Discoloured Nails may help you describe the finding.

Photograph the nail beside a ruler or familiar object, record the date, and repeat the image periodically without altering the nail. Avoid biting, filing deeply, or applying camouflage products if the band is changing. Bring a list of medicines and note any recent injury, rash, or illness. If direct examination leaves uncertainty, the clinician may discuss monitoring or Nail Surgery for a sample or treatment.

Book a dermatology review for a new or evolving band, especially if it becomes broader, darker, irregular, painful, or associated with nail splitting, lifting, or bleeding. Seek earlier care when the surrounding skin also changes or the mark does not move outward as the nail grows. Urgent assessment is sensible after major trauma with severe pain, numbness, or a distorted fingertip.

What features of this band help distinguish pigment from blood or another nail change? Should we photograph and monitor it, and over what interval? Would a nail sample be useful? If surgery is discussed, what part of the nail unit would be examined and how would recovery be managed?