Why does green nail syndrome cause discoloured nails?

Green Nail Syndrome is associated with growth of bacteria in a moist, poorly ventilated space. A nail that has separated slightly from its bed, been injured, or been repeatedly exposed to water can create that space. The bacteria may produce blue-green pigments, so the nail can look green, yellow-green, or darker as the pigment accumulates. The visible colour is within or beneath the nail plate, rather than simply on its surface.

The affected nail may also feel loose or develop an unusual odour, but some people notice colour change alone. Other nail problems can also alter colour, so examination helps distinguish this condition from a fungal infection, trauma, staining, or another nail disorder.

Keep the nail clean and as dry as practical, and dry carefully after washing. Avoid picking, scraping, or covering the discoloured area with artificial nails or polish while it is being assessed. Trim only loose edges carefully; do not pull attached nail from the bed. A clinician may recommend a topical or other treatment after examining the nail, and the altered colour may remain until the affected nail grows out.

Arrange an assessment if the colour change persists, spreads, follows nail separation, or affects several nails. Seek prompt care for increasing pain, warmth, swelling, pus, bleeding, or redness extending into the surrounding skin. People with diabetes, reduced immunity, or poor circulation should arrange medical advice early for a changing nail.

Ask whether the nail needs testing to separate bacterial pigment from fungal disease, whether any loose portion should be trimmed, and how to protect the nail from repeated moisture or injury while it grows.