People get tattoos for various reasons, on various parts of their bodies and in varying sizes. According to the U.S. Food & Drug Administration (FDA) that cited a 2015 Harris Poll, almost 30 percent of all people in the country have at least one tattoo, but new research suggests there might be inherent risks involved in getting this particular form of body art.

More often than not, people tend to check out the work of the specific tattoo artist they are considering, as well as the hygiene practices of the establishment where they plan to get inked. And usually, the safety checks and concerns stop there.

An FDA advisory suggests the ink used in tattoos could be harmful as well, and that it isn’t easy to tell good ink from bad ink.

“While you can get serious infections from unhygienic practices and equipment that isn’t sterile, infections can also result from ink that was contaminated with bacteria or mold," reads the FDA advisory report. "Using non-sterile water to dilute the pigments (ingredients that add color) is a common culprit, although not the only one."

Researchers from Germany and France used the European Synchrotron Radiation Facility (ESRF) to study how tattoo ink travels inside the body, and found that “various organic and inorganic pigments and toxic element impurities” make their way to lymph nodes of the body in the form of nanoparticles. Lymph nodes are part of the lymph system — an important component of the body’s immune system.

“When someone wants to get a tattoo, they are often very careful in choosing a parlor where they use sterile needles that haven’t been used previously. No one checks the chemical composition of the colors, but our study shows that maybe they should,” Hiram Castillo-Michel from ESRF, one of the authors of the study on the topic, said in a statement Tuesday.

Other than organic color pigments, tattoo inks also contain a number of preservatives and contaminants that include chromium, cobalt, manganese and nickel, and others. Carbon black is the most common ink pigment, and is organic in nature, but titanium dioxide — the second-most common pigment which is white — can delay healing of the skin and cause swelling and itching.

These particles make their way to the lymph nodes at the nano scale, a fact that was brought to light for the first time by the study. Previously, it was thought the particles traveled inside the body only at micro scales, and the bigger size meant they were not thought to reach the lymph nodes.

“The lymph nodes become tinted with the color of the tattoo. It is the response of the body to clean the site of entrance of the tattoo. What we didn’t know is that they do it in a nano form, which implies that they may not have the same behavior as the particles at a micro level. And that is the problem: we don’t know how nanoparticles react,” Bernhard Hesse, one of the study’s two lead authors and a visiting scientist at ESRF, said in the statement.

The scientists used skin and lymphatic tissues from human cadavers to conduct their research. The open-access study, titled “Synchrotron-based ν-XRF mapping and μ-FTIR microscopy enable to look into the fate and effects of tattoo pigments in human skin,” appeared online Tuesday in the journal Scientific Reports.