Tattoos are becoming more common. According to a 2023 Pew Research Center survey, about 1 in 3 American adults has at least one. This is especially true for people under 50 and women. This increasingly popular form of self-expression may come with some health risks, though, according to a new study.

Researchers at the University of Southern Denmark (SDU) recently investigated whether people with tattoos have a higher rate of skin cancer and lymphoma, as prior research has suggested this may be the case. The team says that tattoo ink can enter the bloodstream and accumulate in lymph nodes, a key part of our immune systems. The concern is that this accumulation could lead to chronic inflammation that may promote abnormal cell growth.

Henrik Frederiksen, study co-author and clinical professor at SDU, explains, “We can see that ink particles accumulate in the lymph nodes, and we suspect that the body perceives them as foreign substances. This may mean that the immune system is constantly trying to respond to the ink, and we do not yet know whether this persistent strain could weaken the function of the lymph nodes or have other health consequences. Studying this link is challenging because cancer can take years to develop. This means that exposure in youth may not lead to illness until decades later, making it difficult to measure a direct effect.”

To study the possible link, Frederiksen and the rest of the team used data from twin studies, including the Danish Twin Tattoo survey, and figures from the Danish Cancer Registry. In all, the data on thousands of twins were included.

According to the study’s findings, published in the journal BMC Public Health, there was a higher risk of skin cancer in those with tattoos, along with a nearly three times higher risk of lymphoma in twins with large tattoos, defined as those bigger than the palm of a hand.

The researchers say using data from twins is a good way to investigate whether certain factors influence cancer development, as the siblings would have had largely the same genetic and environmental exposures.

The team says the study suggests there’s a higher risk of lymphoma and skin cancer in people with tattoos. Going forward, they recommend studies into how tattoo ink may cause cancer and how ink impacts lymph nodes, especially over long periods. Research into impacts of different colors of tattoo ink could also yield results.

Signe Bedsted Clemmensen, the study’s first author and assistant professor of biostatistics at SDU, says, “In our study, we do not see a clear link between cancer occurrence and specific ink colors, but this does not mean that color is irrelevant. We know from other studies that ink can contain potentially harmful substances, and for example, red ink more often causes allergic reactions. This is an area we would like to explore further.”