This Is What Really Happens Underneath Your Fingernails If You Don't Clean Them

The gunk under your fingernails will typically be gray in color. If it turns green, however, it can signal bacteria (via Women's Health). Nevertheless, bacteria isn't an uncommon finding under the nails. In a 2017 study of 20 students, which was published in the International Journal of Current Microbiology and Applied Sciences, every single one had bacteria underneath their nails, from pseudomonas to staphylococcus to bacillus. Not one student had bacteria-free fingernails.

"Pseudomonas ... is commonly found on nails and produces a green pigment that nail technicians often refer to as 'the greenies,'" dermatologist Dana Stern told Women's Health. Iron compounds cause the trademark green color, and the infection tends to occur in moist environments, making nails an ideal location (via Nails).

It's particularly prevalent with artificial nails, for a couple of reasons. Not only do false nails have little openings in which bacteria can thrive, but they're longer too, according to Stern. This makes it far easier to attract the bacteria in the first place. As we saw from the study of students, attracting bacteria is unavoidable, but you can at least address the problem before it gets too serious.