There is an open secret among tattoo artists, dermatologists, and the small group of researchers studying the effects of tattoo ink: Red ink causes the most problems.
These problems include rashes—itchy, sometimes painful, and occasionally disfiguring—and pseudolymphomas—benign swellings around lymph nodes that resemble cancers of the lymph system. Both rashes and pseudolymphomas are symptoms of an allergic reaction. While these problems are not unique to red ink, red is the most likely culprit. One student from the Heersink School of Medicine launched a mission to understand why.
Doctors are more likely to see tattoo complications now than ever before. Thirty percent of Americans have at least one tattoo, up from 21 percent in 2012, according to a 2019 poll. A separate study in 2017 estimated the range of post-tattoo complications at anywhere from 2 percent to 30 percent; in that paper’s review of patient cases in Finland, 75 percent of allergic reactions were against the red color.
Until the mid-20th century, the reason for red’s ravages was clear: Red tattoo inks often contained mercury. But as the adverse effects of mercury and other metals became widely known, tattoo artists avoided these inks and manufacturers turned to alternative formulas. Today, manufacturers have largely switched to inks colored by organic compounds instead of compounds including heavy metals, and recent studies have found low concentrations of mercury in commercial inks. But red ink is still the most likely color to cause skin problems.
Tiffany Mayo, M.D., associate professor and director of the UAB Department of Dermatology Clinical Research Unit, discussed this puzzle during a student lecture in 2022. Her description and slides immediately caught the attention of then-third-year medical student Matthew Kiszla, the son of an artist and an artist himself who had cheekily listed a book that he and his mother illustrated among the publications on his medical school application.
“I am a very visual person,” Kiszla said, and even though he does not have any tattoos himself, “that attracts me to tattoos and also to dermatology, with its vivid, dramatic rashes.” Plus, Kiszla was an undergraduate chemistry major. The chemical mystery Mayo described was irresistible, he said—“I just had to know why.”
Kiszla’s interest became a passion to understand the effects of tattoo inks on human health and to advocate for increased attention to safety. In February 2023, Kiszla, Mayo, and another professor in the Department of Dermatology, Craig Elmets, M.D., synthesized results from nine recent studies of tattoo inks worldwide in a review article published in the journal Chemosphere. “Unsafe levels of restricted elements”—including chromium, cadmium, barium, arsenic, and zinc—“continue to be detected across studies, warranting further investigation under a regulatory lens,” they wrote.
“Although the United States is the world’s foremost producer of tattoo inks, they are virtually unregulated at a national level,” Kiszla said. “Tattoo inks can be formulated with a wide range of pigments, preservatives, solvents, and other contaminants, which have been associated with rashes that range from transient to disfiguring.”
And there may be other, hidden effects as well. “The potential systemic implications are unknown,” Kiszla said. “While researchers have found that ink can travel from its site of injection via the lymphatic system and be collected into lymph nodes, they have yet to determine whether this concentration of toxins poses any increased risk.”
Kiszla says Europe, the world’s second-largest market for tattoo ink manufacturers, leads the way in terms of research and regulation.
A series of resolutions introduced in Europe starting in 2003 set maximum allowed concentrations for tattoo ink ingredients; in 2022, these guidelines became binding on all members of the European Union. Nearly all research on the chemical makeup of tattoo inks has been done at European universities, Kiszla notes. In their Chemosphere paper, Kiszla, Mayo, and Elmets compared these new European regulations with the concentrations of metals found in tattoo inks as reported in published studies.
Kiszla then turned his attention to organic inks. He wrote a paper on azo dyes with Lauren Kole, M.D., an assistant professor in the UAB Department of Dermatology—who, like Kiszla, holds an undergraduate degree in chemistry. Organic azo dyes are the new standard for tattoo inks as the industry has shifted from metal-based inks. “Warm tones—yellow, orange, and red—have a high concentration of these azo structures,” Kiszla said.
Kiszla said the fact that red inks still cause the most adverse reactions, as they did in the days of mercury, could be a coincidence but there is not yet enough data to be sure. “Ultimately, I hope the studies support the development of safer tattoo inks,” Kiszla said. “My goal is not to impinge on artistic expression but to make body art as safe as possible and as well understood as possible.”
- Matt Windsor