Can Tattoos Cause Cancer? Researchers Investigate a Potential Link

Metallica’s lead vocalist James Hetfield often lauds Motörhead’s Lemmy Kilmister as one of his biggest inspirations. In 2024, nine years after Kilmister passed away, Hetfield tattooed the ace of spades (the title of one of Motörhead’s most popular tracks) on his right middle finger. But what made Hetfield’s tribute so heartfelt—and eccentric—is the fact that he didn’t just use any tattoo ink but one mixed with a pinch of Kilmister’s ashes.

As morbid as they may sound, cremation tattoos are more common than one might expect. Tattoo parlors, crematoriums, and companies specializing in the production of cremation tattoo inks claim that the practice is safe, or at least that it’s no riskier than conventional tattooing. However, no regulatory body actually governs what can go into tattoo ink and under people’s skin. From human ashes to industrial paint used on cars, just about anything goes.

In 2022, the European Chemicals Agency (ECHA) imposed concentration limits for the thousands of chemicals commonly found in tattoo inks due to concerns over their potential health effects. But in the United States and everywhere else in the world, no such restriction is in place.

In line with ECHA's efforts, some scientists have delved into the potential hazardous effects of tattoos. Over the past several years, a handful of studies have hinted at a potential link between tattoos and certain types of cancer, such as melanoma and lymphoma. Today, most researchers, even those who are involved in this work, note that the link between tattoos and cancer is far from conclusive. However, many believe that it is compelling enough to warrant further investigation. A better understanding of the potential link between tattoos and cancer risk will help people make better informed decisions.

Human Lymph Nodes Retain Potential Carcinogen in Tattoo Ink

In 2019, Signe Clemmensen was a research assistant at Syddansk University when several of her colleagues, who had returned from a conference, asked her, “Did you know that tattoo ink accumulates in the lymph nodes?”

There are hundreds of lymph nodes, which are small bean-shaped organs, throughout the human body. They are teeming with cells that serve as some of the immune system’s first responders. Many lymph nodes are located just under the skin and become visibly swollen when people experience infections.

There had already been a few studies reporting tattoo ink buildup in the lymph nodes, though Clemmensen was not aware of them at the time.^1-3 In one study, researchers investigated the accumulation of black tattoo ink in deceased individuals by sampling tattooed skin as well as the lymph nodes beneath it.¹ They discovered that for most of the sampled individuals, tattoo ink remained in the lymph nodes until death.

In addition to the black pigment, the researchers also found traces of polycyclic aromatic hydrocarbons (PAH) there. This group of chemicals is commonly found in tattoo ink even though the World Health Organization’s International Agency for Research on Cancer (IARC) has flagged some PAHs for their carcinogenic potential.⁴ Benzo[j]fluoranthene, one of the PAHs the researchers found in the tattooed individuals’ lymph nodes, is a possible human carcinogen.

The researchers did not know how much time had passed between when the individuals got their tattoos and when they died, but the study was one of the first indications that tattoo ink’s potentially toxic components could stay in the body for a long time.

“The question is, do they cause any harm there?” said Clemmensen, who upon realizing that little was known on the topic decided to pursue it as a PhD project.

Epidemiological Studies Hint at a Complicated Link Between Tattoos and Cancer

Many substances in tattoo inks are known or suspected carcinogens. In addition to PAHs, heavy metals such as chromium and cadmium, which are carcinogenic to humans, are often present in tattoo inks to produce more vivid colors.⁵ For this reason, Clemmensen thought that the link between tattoos and cancer warranted further investigation.

To this end, Clemmensen and her colleagues conducted a retrospective epidemiological study involving thousands of Danish twins.⁶ In retrospective studies, researchers recruit specific groups of people, for instance, patients with cancer, then look into their past. Clemmensen’s team evaluated the participants’ history of skin cancer or lymphoma as well as tattooing: whether they had tattoos, and if so, what color, how big, and when they got their first one. The study’s results suggested that tattoos were associated with an increased risk of developing both skin cancer and lymphoma—but only if they were larger than palm sized. This trend held true even after the researchers adjusted for the participants’ smoking habits, a behavior known to increase cancer risk. However, other researchers were skeptical.

I think it’s important that people know there’s a biological plausibility, [but] there is still so much unknown.

—Rachel McCarty, International Agency for Research on Cancer

“They merged melanoma and non-melanoma skin cancer, which you never do,” Nicolas Kluger, a dermatologist at the University of Helsinki, wrote in an email. “Furthermore, they did not [inquire] about past sun exposure,” an important risk factor for both melanoma and non-melanoma skin cancers.

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The few other studies investigating the link between tattoos and skin cancer that published around the same time as Clemmensen’s paper seemed to present conflicting evidence. One retrospective study found that tattoos increased the risk of developing melanoma in Swedish individuals, supporting Clemmensen’s finding.⁷ In contrast, a different paper focusing on a population in Utah suggested that having multiple large tattoos might protect people against melanoma.⁸

Some researchers found tattoos’ connection to lymphoma more compelling than to melanoma because findings from these studies were more consistent. Unlike melanoma, lymphoma is also largely independent of behavioral factors like how well people protect their skin from harmful ultraviolet rays, either from natural sunlight or tanning beds. “I’m much more worried about the potential link with lymphomas,” said Jennifer Doherty, an epidemiologist at the University of Utah and author of the melanoma paper.

In a retrospective study, Doherty found evidence that tattoos were associated with a rare type of lymphoma.⁹ Similarly, Christel Nielsen, an epidemiologist at Lund University who led the Swedish melanoma study, discovered that tattoos could raise an individual’s risk of developing lymphoma by about 20 percent.¹⁰ The researchers obtained this number after accounting for factors that are known to increase cancer risk, such as age and smoking.

Nielsen’s work garnered significant attention from both the scientific community and the media—and it was not all positive. In response to Nielsen’s paper, Kluger wrote an opinion piece titled, “A recent study on tattoos and lymphoma does not support a possible association,” in which he pointed out that Nielsen’s results were not statistically significant.¹¹

Milena Foerster, an epidemiologist at the IARC, thought highly of Nielsen’s work, describing it as “one of the most important articles [on the tattoo-cancer connection] that we have so far.” However, Foerster was surprised and puzzled because unlike Clemmensen, Nielsen found that the size of tattoos had no impact on their association with lymphoma. This discovery “challenged the results as a whole,” Foerster said, as well as the researchers’ original hypothesis that the components in the inks were the main reason behind the potential link between tattoos and cancer.

Nielsen agreed that the finding was unexpected. One possible explanation, she speculated, is that tattoos may induce a subtle, long-term inflammatory response in the body, which may in turn cause cancer.

Mouse Study Reveals Tattoo’s Long-Term Immune Effects, Which May Promote Cancer

Immunologist Santiago González from the Institute for Research in Biomedicine in Switzerland and his colleagues recently discovered a link between tattoo ink and chronic inflammation in mice.¹² González didn’t originally set out to make this connection, but he stumbled upon his findings while trying to improve the welfare of his laboratory mice.

To distinguish a mouse from its cage mates, scientists often place ear clips on the animals. But González noticed that the heavy clips seemed to annoy them. “I hate these ear clips,” he said.

When another researcher recommended tattooing, González was eager to try it as a gentler alternative in his upcoming project to investigate the mechanism of action of vaccines. In these types of studies, researchers commonly look at the animals’ lymph nodes. González observed that after tattooing the mice’s feet, their lymph nodes were “super swollen, and they were full of ink, and there was a lot of inflammation,” he said, so the team decided to investigate this further.

In the study, the researchers used mice in a life phase that is equivalent to teenage and early adulthood in humans. They discovered that tattooed mice had a diminished immune response to the Pfizer-BioNTech mRNA COVID-19 vaccine up to two months after they got inked.

But, González said, the effect was very local in that only mice that received the vaccine on the same foot where their tattoo was showed this defective immune response. On the other hand, mice that had the vaccine administered on the opposite foot showed immune responses that were comparable to their non-tattooed counterparts. This suggested that the effect was likely due to tattoo ink’s impact on the mice’s lymph node, as the organ acts locally.

“I was thinking, ‘Wow, I was not really aware that the ink was going to have this effect on the immune system,’” González said.

According to González, tattoos' effects on the immune system could last longer than the two-month interval he and his team investigated in the study. He added that “chronic inflammation is very much connected with cancer,” referring to the widespread idea that inflammatory conditions can promote cancer development and progression.¹³ González also previously linked interleukin-1 alpha, a molecule he found circulating in mice blood months after tattooing, to the spread of melanoma to the lymph nodes.¹⁴ Although González did not directly investigate the link between tattoos and cancer, his findings piqued Nielsen’s interest. González shared that Nielsen recently contacted him, and the two are considering a future collaboration.

“I really appreciated this new study because it clearly demonstrated that [tattoos’ effects] are not transient. I think we’re starting to get the different pieces of the puzzle together,” said Nielsen.

González added, "I think that probably there is a connection [between tattoos and cancer], but there are a lot of open questions that we need to address first.”

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Investigating Tattoo’s Systemic and Long-Term Risks

González thinks that tattoos’ impact on the immune system likely depends on the color of the ink. In his study, he found that black and red tattoo inks were toxic to both mouse and human macrophages, a type of white blood cell that lives in the lymph nodes and plays a key role in activating an immune response. However, cells that were treated with green ink were just as healthy as their counterparts from the control group, which received a saline solution.

“Color makes a difference, and it makes sense because each color is formed by a different composition,” González said. “We need to further evaluate it.”

We need to know the final destination of [tattoo inks] in the body because I don’t think they stop in the lymph nodes.

—Christel Nielsen, Lund University

González also worried that tattoos might have more systemic effects on the body. A previous study had reported the accumulation of tattoo ink in mice liver cells.¹⁵

González said, “Doctors told us that in some patients who were undergoing very massive tattoos, the patients observed some ink in their urine.”

These anecdotes were never published as clinical case reports, so González withheld the physicians’ names and contact information, as well as their patients’. But to him, these accounts indicate that the effects of tattoo inks—at least in the case of very large tattoos—might very well be systemic.

Nielsen agreed, adding, “We need to know the final destination of [tattoo inks] in the body because I don’t think they stop in the lymph nodes.”

While Nielsen seeks a mechanistic explanation for the trends she observed in her retrospective studies, other epidemiological researchers are taking a more forward-looking approach.

To answer whether tattoos could really increase cancer risk more definitively, researchers at the IARC are carrying out prospective studies, which follow people over time, contrasting their retrospective counterparts. All of the epidemiological studies that investigated the link between tattoos and cancer so far were retrospective.^6-10 Prospective studies take a long time—years, sometimes decades—but they do not rely on people’s recollection of the past. Because of this, they are less prone to bias due to the study participants’ inaccurate or incomplete reporting of events.

Foerster currently leads an international effort of prospective studies to investigate the link between tattoos and cancer. Her first, called the Cancer Risk Attributable to the Body Art of Tattooing (CRABAT) study, is based in France, but she is also setting up similar analyses in other parts of the world, including Germany, the United States, and China. For each region, the researchers recruit hundreds of thousands of individuals and perform follow-up assessments every few years.

“We are waiting for cancer cases to occur. It sounds a bit morbid,” said Foerster.

The researchers do not know yet when their studies will be complete, but Foerster shared that they already have some important takeaways by analyzing the CRABAT study participants’ profiles.¹⁶ For example, getting tattoos often co-occur with other behaviors such as smoking and drinking alcohol, as well as sociodemographic factors that commonly associate with higher cancer risk such as lower education, income, and access to healthcare. Foerster noted that past studies failed to consider most of these factors, likely because it is challenging to do so from a retrospective framework.

“We definitely need to take [these] into account in our future work,” she said.

For Tattoo Seekers, Researchers Advise Awareness

As the association between tattoos and cancer remains tentative, researchers must “strike the balance between making sure people are informed without scaring people unnecessarily,” said Rachel McCarty, an epidemiologist at the IARC. McCarty previously led the retrospective work in Utah as a graduate student in Doherty’s group and now works with Foerster on the team’s prospective studies as a postdoctoral researcher.^8-9 “I think it’s important that people know there’s a biological plausibility, [but] there is still so much unknown,” she added.

Nielsen shared that she received many emails from the public—among these, the most frequent question was, “Should I remove my tattoo?” McCarty has received this same question. Both researchers advise strongly against this because lasers, the most common method of tattoo removal, could break down tattoo chemicals into even more toxic substances; these include known and potential carcinogens such as o-toluidine and 3,3′-dichlorobenzidine, respectively.^17-22 “If the tattoo-cancer hypothesis holds any water, removal is theoretically one of the worst things that you could do,” McCarty said. Many researchers also warn that UV may break down tattoo ink components in a similar manner. Findings from a couple of studies in an in vitro human skin model and mice suggest that some tattoo inks may protect cells from UV or delay skin cancer development, respectively.^23,24 However, scientists advise people to protect their tattoo-covered body parts the same way they would their untattooed skin, for example, by applying sunscreen before going outdoors.

For now, most researchers agree that there is not yet enough evidence to definitively link tattoos to cancer, but Clemmensen advised people to be careful anyway. In addition to informing the public about what researchers have found so far, she also said that “it is important to tell people how little we know.”