When a nail changes color, many people immediately suspect a fungal infection. This altered nail color, medically termed chromonychia, can signal various underlying issues. While certain colors are hallmarks of true fungal infections, the vibrant green hue that sometimes appears on a nail plate is a distinct condition with a different origin. Understanding the precise cause behind a discolored nail is the first step toward effective treatment.
The Truth About Green Nail Discoloration
Green discoloration on a nail is typically not a fungal infection, but rather a bacterial one known as Chloronychia, or Green Nail Syndrome. This condition is overwhelmingly caused by the opportunistic bacterium Pseudomonas aeruginosa. This organism thrives in persistently moist and warm environments, such as under artificial nails or in a nail plate separated from the nail bed (onycholysis).
The striking green color, ranging from blue-green to nearly black, comes from pigments the bacteria produce as metabolic byproducts. Pseudomonas aeruginosa secretes two primary pigments: pyocyanin (blue-green) and pyoverdin (greenish-yellow fluorescence). These pigments accumulate in the keratinous layers of the nail, creating the characteristic discoloration.
The condition often affects only one or two nails. It is frequently associated with individuals whose hands are submerged in water for long periods, such as healthcare workers or cleaners.
Colors of True Nail Fungus (Onychomycosis)
Discoloration caused by a true nail fungus (onychomycosis) presents with a different spectrum of colors and physical changes than a bacterial infection. Onychomycosis is primarily caused by dermatophytes, such as Trichophyton rubrum, though molds and yeasts like Candida can also be responsible. These fungi feed on keratin, leading to progressive destruction of the nail structure.
The typical presentation involves a color change that is usually white, yellow, or brownish, often starting at the tip of the nail. In rare cases, certain molds can cause a black discoloration. Fungal infections also cause noticeable physical changes, including significant thickening of the nail plate and a brittle texture.
This thickening, known as hyperkeratosis, occurs as the nail bed reacts to the fungal invasion. It produces excess keratin debris under the nail, which may cause the nail to crumble at the edges.
Treatment Approaches for Discolored Nails
The method for clearing a discolored nail depends entirely on correctly identifying the organism responsible, as treatments for bacteria and fungi are distinct. For Green Nail Syndrome (Pseudomonas aeruginosa), the primary focus is eliminating the moist environment and applying a targeted topical agent. Treatment often involves trimming the detached nail portion and applying topical antiseptics or specific antibacterial solutions, such as ciprofloxacin drops or diluted acetic acid (vinegar).
Conversely, treating onychomycosis requires long-term antifungal therapy, often after a laboratory culture or biopsy confirms the fungal species. Topical antifungal lacquers may be used for mild infections, but they struggle to penetrate the thickened nail plate.
More severe or persistent fungal cases frequently require systemic oral antifungal medications, such as terbinafine, which must be taken for several months. Using an antifungal treatment on a bacterial infection will not resolve the discoloration, emphasizing the importance of accurate diagnosis before initiating any treatment plan.