Green nail syndrome (GNS) is an infection of the nails that leads to a greenish discoloration of nails, also known as chloronychia. The green discoloration varies from blue-green to dark green to bluish-grey. Since the discoloration is underneath the nail, it will not disappear with washing or scrubbing. The condition is usually confined to one or two nails and can involve fingernails or toenails. The nail is usually not painful; however the skin around the nail, including the cuticle, may be swollen, tender, or red.
Green nail syndrome is caused by bacteria called Pseudomonas aeruginosa.
When it grows, it produces hallmark green pigments called pyocyanin and pyoverdin. These same pigments impart the green color of chloronychia.
Two major risk factors predispose to GNS. The first risk factor is when a nail becomes abnormally lifted off the nail bed; this is also known as onycholysis. When the nail is detached from the nail bed, the waterproof seal formed by the skin on the nail is lost. This creates a subungual space that collects dirt and debris and may allow an entry point for P. aeruginosa. Trauma to the area under the nail contributes to onycholysis.
The second important risk factor is a damp environment. Dry skin is rarely colonized or infected by P. aeruginosa. Nails repeatedly immersed in water are susceptible. It should also be noted that wearing tight-fitting shoes for a prolonged time, especially while exercising, is associated with GNS. .
Green nail syndrome responds well to treatment. Therapy consists of cutting the detached portion of the nail, keeping nails dry, and avoiding trauma to the area. Topical antibiotics, such as bacitracin or polymyxin B, applied two to four times per day will cure most patients if continued for one to four months. Alternatively, chlorine bleach, diluted 1:4 with water, is effective in suppressing growth of P. aeruginosa when applied topically to affected nails. Vinegar (acetic acid) has been reported to be useful in this regard as well.