In the medical and scientific world it’s known as pseudomonas. In the salon, it’s more commonly referred to as “greenies.” Whatever the name, it’s an unsightly bacterial infection that makes clients and nail techs see green — literally.
Pseudomonas bacterial infection can occur between the natural nail plate and the nail bed, or between an artificial nail coating and the natural nail plate. Some people mistakenly categorize pseudomonas as a mold, but in reality mold is not a human pathogen.
For years, the term “mold” has been used in the nail industry to describe what are most likely pseudomonas bacteria. The green color visible on the nail that’s often mistaken for mold is a byproduct of the infection and is caused primarily by iron compounds.
This type of bacteria is commonly associated with nails, but it can also settle into other parts of the body, including the eyes. It is common in the environment and sometimes even found in hot tubs, says Phoebe Rich, a clinical associate professor of dermatology at the Oregon Health Sciences University in Portland, Ore.
The risk of pseudomonas can be increased by moisture entrapment. Before a nail infection can occur the surface of the nail plate must be contaminated with bacteria. Once a nail enhancement enters the picture bacteria can become trapped between the natural and artificial nail and grow. Covering the nail plate with an enhancement creates a nearly oxygen-free environment in which these bacteria thrive. They produce a dark green substance — the green color you see visible on the nail.
Pseudomonas can form if the bacteria were on the nail plate and were not thoroughly removed before a coating was applied on the nail, or if bacteria somehow got between the nail plate and the product after the client left the salon.