(CNN) — A Swedish study has found a potential link between tattoos and a type of cancer called malignant lymphoma, but it ultimately calls for more research on the topic, and cancer experts say the possible link is overblown.
The researchers, from Lund University, said they wanted to do the study because so little is known about the long-term health effects of tattooing, despite its continuing popularity.
In the US alone, nearly a third of people have at least one tattoo, a 2023 Pew Research Center survey found.
The study, published in the most recent edition of the journal eClinicalMedicine, involved nearly 12,000 people in Sweden.
From population registries, researchers identified everyone diagnosed with malignant lymphoma between 2007 and 2017 – nearly 3,000 people – and matched them with a group of the same age and gender mix who didn’t have cancer.
Malignant lymphoma is cancer of the lymphatic system, the part of the body that helps fight off germs and disease.
Known risk factors include a weakened immune system caused by illness or immune disorders like AIDS, infections such as Epstein-Barr, age and a family history of the disease.
Some exposure to chemicals like pesticides and herbicides can also increase the risk of lymphoma, in addition to secondhand smoke.
In 2021, the study authors sent questionnaires to the people they had identified, asking about certain lifestyle factors that may increase the risk of this kind of cancer and about whether they had any tattoos.
Even after the researchers factored in things that are known to affect cancer risk like smoking and age, they found that the risk of malignant lymphoma was 21% higher among those who had at least one tattoo.
The finding is only an association, not a direct link, but the study authors emphasised that more research will be needed to flesh out this conclusion.
To the researchers’ surprise, they found no evidence to suggest that the risk increased as the person’s skin was covered in more tattoos.
“We do not yet know why this was the case. One can only speculate that a tattoo, regardless of size, triggers a low-grade inflammation in the body, which in turn can trigger cancer,” said co-author Christel Nielsen, an associate professor in the Division of Occupational and Environmental Medicine at Lund University, in a news release. “The picture is thus more complex than we initially thought.”
The study was not set up to determine what the link between cancer and tattoos may be, if any, but experts are sceptical.
The conclusion is “really overstated,” said Dr. Timothy Rebbeck, an epidemiologist at Dana-Farber Cancer Institute and professor at the Harvard T.H. Chan School of Public Health who was not involved with the research.
“If I were writing that paper, if I were the editor, I would have said the conclusion is, there is no evidence for a strong association,” he said.
The data is solid, he said, but the main risk factors for lymphomas are not found in tattooing.
“I would say the message here should be, we really didn’t learn a lot about whether tattoos are associated with cancer with this, and if I had to make a conclusion, I would say the data suggests there is no association,” Rebbeck said, noting that a smaller 2023 study on a connection between tattooing and lymphomas or hematologic cancer also found no increased risk.
The 21% estimate of added risk comes from the models in the new study, but it is not statistically significant, he said.
Dr. Catherine Diefenbach, director of the Clinical Lymphoma Program at the NYU Langone Health Perlmutter Cancer Center, said some things about the study don’t add up.
“What doesn’t make sense to me is why there’s no correlation with the size of the tattoo. It doesn’t really make sense to me that if there is an immune or toxic response, that the bigger tattoo didn’t have any impact at all on the association,” she said. “There are a lot of questions I have from this study.”
Diefenbach said she’s never been asked about a connection between tattooing and cancer, but she has seen news reports about the new research.
“I think people are getting very nervous about something that is an early study that has to be validated,” she said.
The study authors speculate that if tattoos do increase the risk of a malignant lymphoma, one reason may be because of a problem with the ink itself. Tattoo ink can often have chemicals that are considered carcinogens, including metals and polycyclic aromatic hydrocarbons.
Earlier studies have shown that the ink can sometimes travel through the body, and tiny particles can get stuck in the lymph nodes, which could lead to health problems.
Another study found that tattoo ink could slightly alter parts of blood cells that communicate with others, but it is unclear whether that has an effect on health.
Even infections are rare after tattooing, studies show. In 2023, the US Food and Drug Administration issued draft guidance to the makers of tattoo ink and its distributors to help them recognise when ink may be contaminated after the agency received reports about contaminated inks and some companies recalled those inks.
The FDA will log and investigate complaints against the industry, but it doesn’t regulate the practice or the inks used in tattooing because it’s considered a cosmetic procedure.
Nielsen said her group will look into whether tattoos are associated with other types of cancer or inflammatory diseases such as arthritis, lupus, high blood pressure and heart disease.
Rebbeck notes that these types of research can be tricky for the public to interpret.
He helps run cancerfactfinder.org, which aims to help people understand what does and does not cause cancer. Some have asked about tattoos, but the research doesn’t really show a connection, he says.
“I would say we really don’t know very much, but there’s no strong evidence that having a tattoo is going to cause cancer,” Rebbeck said.
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