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.

Keywords:   mold     nail diseases     pseudomonas  

Required Reading

Under the Microscope: Pseudomonas

March 7, 2012

Familiar to nail techs because it can turn clients’ nails green, pseudomonas is a common bacteria that thrives in many environments.

A Day in the Life of a Nail Doctor

August 19, 2011

A New York City-based dermatologist specializing in nails, Dr. Dana Stern takes us on a tour of her day — complete with melanomas, onycholysis, paronychia, and more.  

What Is Pseudomonas?

March 1, 2009

Oh, that dreaded feeling that comes over a tech when she picks up a client’s hand and spots her green nemesis.


February 1, 2005

Having a nail infection is never fun, but luckily pseudomonas bacteria is one nail disease that can be eliminated fairly easily. Find out what causes the “greenies” and how you can ensure your clients won’t have ever have to deal with this ugly disorder.

Green Monsters

November 1, 1997

Fungal infections of the nails are to nail salons what Elvis sightings are to the National Enquirer — rumored to be everywhere but with no documented proof.

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