Tattoos are more popular than ever. In many places, it is more common to have tattoos than it is to not have them. While most people love their tattoos, they almost certainly will not love the fact that a new paper published in the journal BMC Public Health shows that those tattoos dramatically increase their risk of skin cancer.

The study was conducted by researchers at the University of Southern Denmark and Finland’s University of Helsinki. They looked at medical data from more than 2600 twins and compared the health of a twin who had tattoos with one who did not. This is a great way to conduct a study like this because other factors including genetics, environment, and more will typically be very similar between the two people.

What they found was that the tattooed twin was about 1.62 times more likely to develop skin cancer than the one who had not been inked. When they look at those in the study with larger tattoos (those larger than their hand), the risks were even more dramatic. Those who had bigger tattoos had a three times higher risk than those with no tattoos at all.

The study did not look into why those with tattoos had such elevated risks of cancer, but they did discuss some theories that they had in a press release from the school. In it, they wrote:

“When tattoo ink penetrates the skin, some of it is absorbed into the lymph nodes. The researchers are particularly concerned that tattoo ink may trigger chronic inflammation in the lymph nodes, which over time could lead to abnormal cell growth and an increased risk of cancer.”

The school’s hematologist and clinical professor, Henrik Frederiksen, believes that it may be that the body sees the tattoo ink as a foreign body that it needs to attack and expel. He explains:

“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.”

This is not the first study to be done that shows an elevated risk of cancer associated with tattoos. And, given the popularity of tattoos themselves, it likely won’t be the last. The Denmark-based team has already said that they plan on looking at the molecular level to see how tattoo ink is treated within the lymph nodes in the body to see whether that could be a link to the increased cancer risks.

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