If you live in the US and are planning on getting a tattoo any time soon, we’ve got some potentially unwelcome news. Many common commercial tattoo inks have either different ingredients than those listed on the label or additional substances that are not listed at all, according to a new paper published in the journal Analytical Chemistry. And there are other scientific studies suggesting that some of those ingredients could have adverse health effects, either in the form of allergic reactions or skin or other cancers.
“Our goal is to empower artists and their clients,” said co-author John Swierk, a chemist at Binghamton University. “Tattoo artists are serious professionals who have dedicated their lives to this craft, and they want the best possible outcomes for their clients. We’re trying to highlight that there are some deficiencies in manufacturing and labeling.”
Typical tattoo ink contains one or more pigments (which give the ink its color) within a “carrier package” to help deliver the pigments into the skin. The pigments are the same as those used in paints and textiles. They can be either small bits of solids or discrete molecules, such as titanium dioxide or iron oxide (for white or rust-brown colors, respectively). As for the carrier packages, most ink manufacturers use grain or rubbing alcohol, sometimes with a bit of witch hazel added to the mix to help the skin heal after the tattooing process. There may also be other additives to adjust the viscosity and keep pigment particles suspended in the carrier package.
Swierk was initially interested in tattoos as tools for medical diagnostics. This shifted to an interest in tattoo laser removal, specifically how laser light causes tattoos to fade—i.e., break down chemically—which in turn inspired him to learn more about the chemical composition of tattoo inks, which is also not well understood. Even the tattoo artists Swierk’s team interviewed knew very little about the chemical composition of their favorite inks.
Thus the online project What’s In My Ink was born. According to the project’s mission statement:
In modern times, tattooing is often associated with being young and reckless. However the truth is that tattooing is an ancient art having been around for roughly 5000 years. Within the last decade, the frequency of Americans getting a tattoo has increased by 9 percent with 30 percent of Americans now having a tattoo. Despite the vast history of tattooing, and the increased frequency of tattoos in modern society, tattoo inks are generally not regulated by the government, nor does the government have any specific knowledge about the molecular composition of most tattoo inks.
Swierk et al. use various methods, including Raman spectroscopy, nuclear magnetic resonance spectroscopy, and electron microscopy, to analyze a broad range of commonly used tattoo inks. This enables them to identify specific pigments and other ingredients in the various inks. They presented preliminary results at a 2022 meeting of the American Chemical Society. They found that many ingredients didn’t appear on the manufacturers’ labels, such as one ink that contained ethanol even though it was not listed on the label. And 23 of the inks analyzed by that point showed evidence of an azo-containing dye. Such pigments are usually inert, but exposure to bacteria or UV light can cause them to degrade into a nitrogen-based compound that could potentially cause cancer.
This new paper incorporates that early data (now peer-reviewed) and expands upon it. The team has now identified 45 out of 54 inks (90 percent) with major labeling discrepancies, including different pigments than those listed or unlisted additives. Allergic reactions to the pigments, especially red inks, have already been documented. For instance, a 2020 study found a connection between contact dermatitis and how tattoos degrade over time. But additives can also have adverse effects. More than half of the tested inks contained unlisted polyethylene glycol—repeated exposure could cause organ damage—and 15 of the inks contained a potential allergen called propylene glycol.
The study has some limitations, notably the exclusion of many other manufacturers of tattoo inks, although the sampling of nine manufacturers “run[s] the gamut from extremely large manufacturers to small producers,” the authors noted, adding that “there is a reasonable cause for concern that labeling issues are likely to extend to other inks not included in this study.” Also, Swierk et al.’s study focused on concentrations of 2,000 parts per million, compared to a range of 2 ppm required by European regulations. The authors suggest that there could be even more unlabeled substances in tattoo inks at lower concentrations than the ones they’ve identified thus far. The next phase of the project will be to analyze blue and green inks sold in Europe.
The European Commission has recently begun to crack down on harmful chemicals in tattoo ink, including two widely used blue and green pigments (Pigment Blue 15 and Pigment Green 7), claiming they are often of low purity and can contain hazardous substances. In the US, manufacturers of tattoo inks have historically not been required to disclose the ingredients, and even when they did, there was no real oversight of whether those disclosures were correct. That is beginning to change with the passage by Congress of the Modernization of Cosmetics Regulation Act (MoCRA) in late 2022. The law enabled the FDA to regulate tattoo inks for the first time, including monitoring accuracy in labeling tattoo inks. The regulations are less strict than those adopted by the European Union, but they’re a start.
“We’re hoping the manufacturers take this as an opportunity to reevaluate their processes and that artists and clients take this as an opportunity to push for better labeling and manufacturing,” Swierk said. “The FDA is still figuring out what that is going to look like, and we think this study will influence the discussions around MoCRA. This is also the first study to explicitly look at inks sold in the United States and is probably the most comprehensive because it looks at the pigments, which nominally stay in the skin, and the carrier package, which is what the pigment is suspended in.”
DOI: Analytical Chemistry, 2024. 10.1021/acs.analchem.3c05687 (About DOIs).