For years, this symptom was simply dismissed as “algae,”

and it was widely believed within the profession that although nail technicians cannot eliminate the discoloration, it is certainly not infectious and that artificial nail products can safely be applied over such nails. This assumption wasn’t even questioned when returning clients presented with even more nails covered in unsightly green or grayish-green spots.

It’s time to take a closer look at the origins of these not just cosmetically unattractive but, in worse cases, infectious green spots.

What Causes Green Nail Syndrome?

The most common cause of green surface infection on the natural nail plate is the bacterium Pseudomonas aeruginosa.

Where can we encounter this bacterium?

Practically anywhere. It can be found on humans, animals, plants, and even in soil. It thrives in moist environments, such as baths, washing machines, and dishwashers. It appears in high concentrations in hospitality venues, swimming pools, and healthcare facilities. Despite this, very few people seek medical treatment for the infection, as it typically appears on the nails of otherwise healthy individuals. The symptom is also widespread among those who wear artificial nails, yet few seek medical help for the infection, even though the bacterium is far from harmless. In severe cases, it can cause blindness if it gets into the eyes, and it can also cause pneumonia, urinary tract, or even internal genital infections.

How Can We Detect the Presence of the Bacterium on Nails?

During diagnosis, visual inspection clearly reveals bright green, lettuce green, darker green, or, in acute cases, greenish-brown spots. Typically, these are odorless, but if a green nail plate has an unusual smell, it may indicate a secondary fungal infection. This symptom can occur on nails that have never had artificial enhancements, though this is less common. Today, the phenomenon has grown into a serious and concerning problem among wearers of artificial nails, where the aforementioned bacterial infection has become increasingly prevalent. Elderly or chronically ill individuals, especially those hospitalized, are particularly susceptible, but it can also affect healthy people not undergoing any medical treatment.

Scientific articles note that susceptibility and contact with the bacterium are sufficient for infection—such as touching the faucet in a public restroom. Even water splashing back from a sink can carry bacteria. A useful tip is to always carry a skin disinfectant and use it after every public restroom visit. Medical facility restrooms, institutions, gas stations, stadiums, and public baths are particularly risky in this regard.

How Can the Infectious Bacterium Get Under a Sealed Artificial Nail?

There are mainly two scenarios.

• First, water containing the bacterium gets under a lifted artificial nail. Since the pathogen is nearly everywhere, it only needs suitable conditions to multiply. This bacterium loves temperatures between 36–40°C and moisture; it does not need light to thrive. Nail lifting has always been a significant risk for artificial nail wearers, so as professionals, we must focus on preventing lifting or, if it occurs, reconstructing it immediately. It’s always simpler and better to replace a lifted nail than to deal with a bacterial infection and risk our reputation. In this scenario, the nail technician is almost always responsible for the concerning condition. To prevent this, it’s advisable to inform every client (preferably with a signed statement) that if they suspect or notice lifting, they should immediately contact their nail technician. Not only P. aeruginosa but many other bacteria and fungi can proliferate under a lifted nail.
• The second scenario is when, during a refill or new application on an apparently well-sealed nail, a green spot appears on the natural nail plate. In this case, the argument that anything could have penetrated between the natural nail and the artificial nail is invalid.

So how did the bacterium start multiplying on a surface that was supposedly dry and disinfected?

It could only be present if it was already on the client’s hand/nail upon arrival, and inadequate disinfection failed to eliminate it. Alternatively, contaminated tools could have introduced it onto the keratin layer.

How Can We Prevent Bacterial Infection During Nail Enhancement?

With more thorough and careful disinfection than ever before. This should always start with washing hands with disinfectant liquid soap and a nail brush. Skipping this is a significant risk before starting any hand or nail service. Mechanical contaminants must be thoroughly removed from skin folds according to proper handwashing protocols.

When Should We Wash Hands with Disinfectant Soap and When Is Hand Sanitizer Sufficient?

Handwashing with soap is a mechanical cleaning process, rubbing the liquid soap on the hands for 0.5–1 minute to cover all areas, including nail beds, fingertips, and thumbs, then rinsing under running water and drying with a disposable paper towel. However, this does not sufficiently reduce the number of pathogens, even with extended washing time. When turning off non-lever taps or touching water droplets colonized by water-loving bacteria (like Pseudomonas aeruginosa), hands can be recontaminated. Therefore, after handwashing, always rub a broad-spectrum hand sanitizer into the skin. This is expected from both the client and the technician.Disinfectant handwashing is an essential first step before any service. Additionally, repeat the two-step disinfection (handwashing + sanitizer) whenever the client touches their bag, pocket (preferably avoid this), or leaves for the restroom. Wet areas should be disinfected daily, as they are high-risk zones for P. aeruginosa.

Is Everyone at Risk?

Fortunately, not everyone is at risk. Since P. aeruginosa is not part of the normal skin flora, infection of intact nails is rare. Most pathogens settle on or infect damaged nails, but unfortunately, natural nail plate injuries are not uncommon in the nail industry. Stress fractures from a wrong move or choosing an unsuitable nail length for one’s lifestyle can also cause problems.

Any treatment, procedure, or beauty service involving direct contact with the skin or nail surface must begin with a thorough disinfection protocol, considering all circumstances. During the service, clients should avoid touching other skin areas, their nose, ears, or scalp. Before disinfection, take care of any activities that could expose you to new sources of infection during the service.

What If a Client Comes from Another Technician and a Green Spot Is Found After Product Removal?

Any symptom deviating from a healthy state is a sign of disease and is a contraindication for nail enhancement, gel polish, or any hand or nail service. So, yes, Pseudomonas aeruginosa infection is also a contraindication. Filing (which only spreads the pathogen) or using acidic primers, as some do, will not solve the problem. The nail technician cannot cure or eliminate the infection. A specialist will prescribe antibiotic treatment, which cannot be replaced by home disinfectants. Nail technicians are not doctors and should not perform such treatments.

Conduct thorough preventive, two-step disinfection, inform clients about proper artificial nail care, and advise them to seek repairs immediately if they notice lifting. Do not file the natural nail plate too thin, as this increases the risk of lifting. Modern prep techniques should avoid capillary bleeding and other nail injuries. Following these guidelines can almost entirely eliminate the risk of green nail syndrome caused by Pseudomonas aeruginosa.

Summary

Green nail syndrome is an increasingly common issue in the nail industry, but with proper attention, adherence to hygiene rules, and client education, it can be largely prevented. If a green spot does appear, do not attempt home treatment or apply new products over it—consult a dermatologist for professional care. Nail health is our shared responsibility—because beauty can only be lasting and safe on a healthy foundation.