What should you know about diffuse melanonychia?

Melanonychia describes pigment in the nail plate. Diffuse melanonychia may involve several nails and can appear as an even wash of colour or as multiple bands. Melanin production can increase naturally, especially in people with darker skin tones, and can also change with repeated friction, nail injury, inflammation around the nail, or some medicines. Certain medical conditions can affect several nails as well. A clinician may examine the nail surface and the skin around it, ask when the colour began, review medicines, and look at other nails and skin findings.

The appearance alone cannot identify the cause. A dark nail can also reflect blood beneath the nail, infection, or another nail disorder. Diffuse colour across several nails is a different pattern from a newly appearing, irregular band confined to one nail, but both deserve context-based assessment when the change is unexplained. Do not scrape, bleach, or repeatedly file the nail to remove the colour; those actions can injure the nail and make its pattern harder to judge.

Photograph the nails in good light and note which nails are involved, whether the colour reaches the cuticle, and whether the pattern is changing. Arrange a dermatology appointment for unexplained diffuse pigmentation, particularly if it started after a new medicine or follows nail inflammation. Bring a list of prescription medicines, supplements, and recent nail trauma. A dermatologist may use magnification and, when the appearance remains uncertain, may discuss testing or a nail biopsy. Treatment depends on the cause rather than the colour itself; a suspected medicine should not be stopped without advice from the prescriber.

Seek a prompt dermatology review if pigmentation is new, rapidly changing, becoming darker or wider, or developing uneven edges. Arrange assessment sooner if colour extends onto the surrounding skin, the nail splits or lifts, or there is pain, swelling, bleeding, a nodule, or persistent tenderness. These signs do not establish a diagnosis, but they should not be watched indefinitely. If several nails changed after a clear medication change or a period of repeated trauma, mention that timing when booking.

Useful questions include: Which nails and features are you assessing? Could friction, inflammation, infection, or a medicine explain this pattern? Should I monitor it with photographs, and over what interval? Would testing or a biopsy add useful information? What nail care should I avoid while the cause is being clarified?