We don’t know if the ink reaches the kidney, liver or lungs.

A recent study of the Lund University, in Sweden, found an increased risk of lymphoma in people who were tattooed. The team, led by doctor Christel Nielsen, included all patients with this type of hematological cancer, detected between 2007 and 2017, reflected in the Swedish National Cancer Registry. Nielsen is an epidemiologist and her career has focused on how chemicals in today’s world affect health, and regarding tattoos, she believes that very little is still known. Therefore, she has proposed to change it. While the research she has conducted is still early, she believes she has a great future ahead of her.

—What substances do the inks used in tattoos contain?

—Basically, they are mixtures of different chemicals. We know many of them from before, from other uses. Depending on the color, the components vary. In general, we have heavy metals, such as arsenic, chromium or cobalt, in all inks. The black ones contain polycyclic aromatic hydrocarbons (PAHs); and the most colorful inks contain azo derivatives, many of which are banned in the European Union, because when exposed to the sun, laser, or a heat source, they degrade into aromatic amines, which are potentially carcinogenic.

—How is it possible that these substances are present in the ink? Especially in the European Union, which is characterized by very strict security controls.

—Yes, totally. We have European legislation since 2022, with which they tried to establish a series of limits on the concentrations of many of these chemicals, but beyond this, I do not have an answer to your question. That’s partly why I started the investigation, because it seems very strange to me that we didn’t have anything. Some countries had legislated on their own in this regard. Personally, one of the reasons that may explain this situation is that this issue has been overlooked, because many of these chemicals are used in the world of cosmetics or makeup, for example, but the use in tattoos, which are injected in the body, it has been ignored.

—What was the initial idea that made you start the investigation?

—My specialty is environmental epidemiology, so I research chemicals in our environment and how they affect our health. I may have one or two tattoos (laughs). So, out of curiosity, I decided to look at what science said about its effect. I was amazed when I saw that there were almost no studies on the matter. When I started to get into the matter, I realized that a lot of attention had been paid, on a general level, to the substances present in the ink. So, we knew that there could be certain toxic components in them; Other studies had concluded that the pigment could migrate from the skin to the lymph nodes. In fact, it has been seen that it could be a fairly large part that moves from the skin and goes to another part of the body. So my curiosity focused on whether all of this could lead to an increased risk of disease.

—Once we get a tattoo, what happens to our body?

—The pigment is introduced into the lowest layer of the skin, where the blood vessels and lymphatic vessels are. So, basically, we put these external particles in, and the organism perceives it as an intruder, as something that should not be there. So the immune system is activated. That is, when someone gets a tattoo there is an immune response, for example, the skin turns red. And during this process, there are specific cells of the immune system that take that pigment and take it to the lymph nodes to fight against them. It is even possible that they lead to other parts of the body, but we don’t know yet.

—In other words, it is an assault.

—Yes, totally. Like a virus. That is, you have something in your body that shouldn’t be there and your immune system tries to eliminate it.

—Many of us have tattoos. If we stop to think about it, this practice doesn’t make much sense, right?

-Clear. I am very Swedish and I thought that, if you can go to a studio and get a tattoo by paying for it, it would have to be something safe, because in Sweden everything is very safe, of course. That’s what I thought.

—What were the conclusions of your investigation?

—What we saw is that participants who had tattoos had a greater than 20% risk of developing lymphoma compared to those who did not have them. But it is true that this is the first study that has been done on a large scale, so it is too early to draw firm conclusions about whether a tattoo could cause cancer. We need more research. Although I think the results will follow this direction.

—In the study they pointed out that the effect increased, in a group of patients, in the two years following getting a tattoo, and in another group of people, in a time greater than a decade. Why this time jump?

—S. I think it makes sense if we understand how a cancerous tumor develops. Because we can have a process that starts it, but lymphoma, for example, is an entity that takes many years to develop, between 10 and 15. We were surprised to see the statistics of that group of people in which the growth was two years or less. We believe that it could have been due to two factors: either that the person already had the cancerous process underway, or that the tattoo acted as a trigger. These are hypotheses.

—Did you see if the size of the tattoo increased the risk?

—No, we didn’t see that size mattered. In fact, it wasn’t what she expected. She expected that the bigger it was, the more ink and therefore the more toxic it would be. But we couldn’t confirm it. It is also true that we only studied the effect on lymphoma. It is possible that, since the lymph nodes are small, they are only capable of taking up a certain amount and the rest is distributed to another part of the body or discarded by the body. We do not know. It is also true that not being able to establish the difference between a small tattoo and a large one could be due to the methodology of the study, because people were not able to distinguish what is one and what is another.

—It says that the ink could be distributed or it could be eliminated. This is like saying that it is unknown what happens with it in our body.

—Yes, totally. We do not know. It’s hard to believe and even insulting. Why hasn’t anyone stopped to study this before? It makes me angry to think that so many people are tattooed and we hardly know anything about it.

—Red ink is the one to which the most health reactions are attributed. Is there anything special?

—Yes, it is very related to allergic reactions, for example. As I said, there is a lot that we don’t know. That is, we do not know if it is due to the specific chemicals in the ink or the fact that we have particles of it in our body, which stay there, and can activate our immune system. We tried to look at the effect color by color, but we didn’t see a big difference. It is also true that this could be explained because almost all of us have black tattoos, and fewer have other colors.

—Where do you think you will continue this line of research?

—First of all, I think we need more similar studies to see if the results are repeated in different populations or countries. But I also think it is necessary to see what happens in other types of cancer, because we do not know if the ink reaches the kidney, the liver or the lungs. And then, I think it would also be interesting that, if we see that it has an effect on cancer, it could mean that the immune system is altered and could be a trigger, in turn, of autoimmune diseases.

—Are you planning to follow her yourself?

—S. And I am very excited that postdoctoral researchers are becoming more and more interested. We have a chemist who is going to focus on the chemicals in the inks, and another colleague who will focus on how much is wasted. To do this we are going to collaborate with a tattoo studio in Lund, which will put us in contact with their clients to draw blood before and after the tattoo.