Got inked? One in four Swedes has a tattoo, and among young women they are even more common. But what exactly has been injected into your skin? We spoke to researchers who know more.
Photo: Åsa Bongnell-Höjer
Text: Annika Lund, first published in Medical Science, issue 3, 2026
There are differing estimates of how common tattoos are. According to the latest environmental health survey from Sweden’s Public Health Agency, one in four Swedes has decorated their skin, and tattoos are now more common among women: 28 per cent of women and 21 per cent of men say they have been tattooed. Among both sexes, tattoos are more common in younger age groups. Small, single-colour designs dominate, while large, colourful tattoos are most common among younger men. The vast majority experience no problems from their tattoos.
For some people, however, tattoos lead to prolonged skin problems. In the Public Health Agency survey, 4.7 per cent reported skin problems due to their tattoo. Some struggle with troublesome contact allergies, where the ink causes intense itching. There are other complications too, which we will return to later in the article.
But let us start at the beginning. How does tattooing actually work? Why does the ink remain in the skin? Or does it?
A tattoo machine makes tens of thousands of needle punctures per minute and is continuously supplied with ink. The aim is to place pigment particles in the dermis, the middle layer of the skin, around one to two millimetres below the surface. If the ink is deposited too superficially, it disappears as the skin renews itself. If it is deposited too deeply, the design can become blurred.
When the ink reaches the dermis, the body’s immune system reacts, particularly macrophages, the immune system’s “big eaters”. They engulf the pigment particles but are unable to break them down in the same way they would normally break down bacteria. The pigments are highly stable and remain inside the immune cells.
When those cells eventually die, the pigments are released locally, where new macrophages engulf them. The result is a slow, local cycle in which the ink is transferred from one immune cell to another. French researchers demonstrated this in a mouse study published in 2018. It was the first time anyone had managed to explain why a tattoo remains visible despite the constant turnover of cells, explains Nanna Fyhrquist , an immunology researcher at the Institute of Environmental Medicine at Karolinska Institutet.
“Most pigment particles remain within macrophages, passing from one generation of cells to the next,” she says.
Pigments reach the lymph nodes
But the “big eaters” are affected by being filled with pigment. This was shown in a Swiss study from 2025 in which researchers examined mice whose hind paw pads had been covered with tattoos. In a human, the tattooed area would correspond to roughly the size of a palm.
The researchers were able to follow several immunological reactions in real time. Within ten minutes, pigment particles had reached lymph nodes near the mouse’s “knee”, where a clear immune response was triggered.
A large proportion of the ink remained there. This is in line with earlier post-mortem studies in humans showing that nearby lymph nodes take up tattoo pigments.
However, in this mouse study the researchers saw that some of the pigment travelled further through the system. It reached lymph nodes in the abdomen.
“It is important to know where the pigments end up. Do they remain in the first lymph nodes, or can they move on through the body? In this mouse study, some pigments travelled further, but we do not know whether the same happens in humans,” says Nanna Fyhrquist.
The Swiss study showed that macrophages in the tattooed area were almost crammed full of pigment particles. This was expected, as that is what makes a tattoo permanent. However, the researchers were also able to show that this affected how well the immune cells functioned.
When the mice received an mRNA vaccine against COVID-19, they produced weaker antibody responses than control mice that had not been tattooed. But when they were given an influenza vaccine based on a different vaccine technology, they instead produced stronger antibody responses.
This suggests that tattooing affects the way the immune system responds, at least in mice.
But does any of this matter? Do altered vaccine responses in mice, the transport of pigment particles to lymph nodes and their onward movement through the lymphatic system have any relevance for someone who wants to mark a milestone in life? To engrave something that reflects deep emotions into their skin? Or simply to feel good?
Researchers simply do not know, says Nanna Fyhrquist.
“I do not want to be a doom-monger and frighten someone who really wants a tattoo. But as an immunology researcher I cannot ignore the fact that the mice’s immune systems were affected. At the same time, these are animal studies and we do not know whether the findings also apply to humans,” she says.
What does the word tattoo mean?
The word tattoo comes from the Polynesian word tatau, meaning roughly “to strike” or “to tap”. The word entered English during the eighteenth century following James Cook’s voyages in the Pacific, and from English it was subsequently adopted into other languages.
Many tattoo inks undoubtedly contain substances that may be harmful to health. Black ink often contains carbon black, a carbon-based pigment commonly used to protect the rubber in car tyres from UV radiation. Older tattoo inks were often metal-based, with cadmium producing yellow, orange and red shades, chromium green, mercury red and cobalt blue.
Metal-based inks, however, often have duller tones. Over the past few decades, inks containing azo pigments have come to dominate because they produce bright and vivid colours. When azo pigments break down, carcinogenic substances may be formed. Tattoo inks also contain solvents, binders, preservatives and sometimes other additives.
The colours are not pre-approved
As with all toxic substances, however, the dose matters. Since 2022, the EU’s REACH chemicals legislation has restricted the levels of toxic substances in tattoo inks. Particular attention is paid to substances that may be carcinogenic, affect fertility or cause allergies.
There is, however, no system of pre-market approval. No authority approves tattoo inks before they are sold.
“No, because these chemicals were not designed to be used in the skin, or indeed anywhere in the body,” says Ina Anveden Berglind, consultant dermatologist at the Centre for Occupational and Environmental Medicine in Stockholm and affiliated researcher at the Institute of Environmental Medicine at Karolinska Institutet.
The Swedish Medical Products Agency is the regulatory authority for tattoo inks. During 2024, tattoo studios in around one hundred municipalities were inspected. A total of 445 tattoo inks were reviewed during these inspections.
More than half failed to meet REACH labelling requirements. In many cases, the ingredient list itself was inadequate.
“When the labelling contains such serious shortcomings, even a highly reputable tattoo studio cannot guarantee that the ink actually complies with the regulations,” says Ina Anveden Berglind.
There has long been concern that tattoos might increase the risk of cancer, particularly lymphoma and skin cancer. In Sweden, researchers have sent questionnaires asking about factors such as the size and colour of any tattoos to people with lymphoma and various types of skin cancer identified through the national cancer registry. Matched control participants without corresponding cancer diagnoses received the same questions.
The Swedish studies found statistical associations. People who had developed lymphoma or melanoma were somewhat more likely to be tattooed than the controls. No corresponding association was observed for squamous cell carcinoma. The studies attracted considerable attention, particularly the one on lymphoma.
But how should they be interpreted?
With great caution, says Maria Feychting , Professor of Epidemiology at the Institute of Environmental Medicine at Karolinska Institutet.
“There are still relatively few studies in this field, and they have produced uncertain results,” she says.
Uncertain cancer findings
One source of uncertainty highlighted by Maria Feychting is the low response rate. Only just over half of those who had had cancer responded to the questionnaire, and among the controls the proportion was even lower. This applied to both the lymphoma and melanoma studies. In some cases, a long time had passed between the tattoo and completion of the questionnaire, which may have led to inaccurate recollections of factors such as sun-exposure habits.
Nor was a clear dose-response relationship observed. Large tattoos were not associated with a higher cancer risk. In the lymphoma study, the cancer risk was highest during the years immediately following tattooing, which is unexpected given that cancer takes time to develop. In the melanoma study, most tumours occurred outside the tattooed area.
A review of seven earlier studies, including the Swedish ones, was recently published. According to the review, there is currently no convincing evidence that tattoos increase the risk of skin cancer or lymphoma.
“We are surrounded by many carcinogenic substances, and they are present in tattoo inks too. That does not necessarily mean that tattoos increase the risk of cancer. We need more robust studies before we can provide clear answers,” says Maria Feychting.
Such studies are already under way.
What is already certain is that tattoos can cause infections and skin reactions. As for infections, the message can be brief: the risk is low if you go to a reputable tattoo studio with good hygiene standards.
Skin reactions, however, can become a prolonged affair. Unfortunately, they cannot be prevented simply by choosing your tattoo artist carefully.
“People respond differently to the various substances found in tattoo inks,” says Ina Anveden Berglind.
In general, the risk of long-term skin problems appears to increase with the size of the tattoo. Available figures show that 12 per cent of people with large tattoos, covering an area greater than five palms, experience skin problems, compared with 2 per cent of those with smaller designs.
Red ink comes with warning
Red ink comes with its own warning flag. Red tattoos are more likely to cause problems in strong sunlight, known as phototoxic reactions. In one study, more than one in five tattooed individuals reported sun-triggered reactions in which the tattoo would almost immediately begin to itch, become red, swell or hurt.
“These problems can be managed by covering the tattoo with clothing, but if it is located on the hands, neck or similar exposed areas, that becomes more difficult. It is also not much fun always having to wear long trousers in the sun if the tattoo is on your legs,” says Ina Anveden Berglind.
Another long-term skin problem is contact allergy, an allergy to one of the substances in the tattoo ink. It can cause utterly unbearable itching, severe enough to make the tattoo difficult to live with. This is particularly troublesome because contact allergy is lifelong, while the tattoo is permanent.
“Sometimes there is no alternative but to remove the tattoo surgically. If it covers a large area, the area may need to be covered with skin grafts afterwards,” says Ina Anveden Berglind.
The most common method of tattoo removal is laser treatment. In cases of contact allergy, however, it may do more harm than good.
When the laser hits the tattoo, the pigment particles are broken down into smaller fragments. This makes it easier for the immune system to remove them, causing the tattoo gradually to fade.
“But the particles are only removed from the skin, not from the body. We want to avoid spreading pigment particles that can trigger contact-allergic reactions to the rest of the body,” says Ina Anveden Berglind.
Steroid injections into the itchy area may provide relief, although the treatment usually needs to be repeated. In the best cases, a more lasting effect may be achieved with a JAK inhibitor cream. According to a relatively recent study, this immunosuppressive medicine, which is used to treat hand eczema, completely relieved two patients of their itching.
“The substances introduced into the body when you get a tattoo are not harmless. I think people should consider their tattoo very carefully and be aware that the risk of skin problems increases if the designs are large, colourful or contain red ink. At the same time, I do not lose sleep over the risks of tattoos, and the desire to decorate our bodies appears to be deeply rooted, since we have been doing it for thousands of years,” says Ina Anveden Berglind.
Note: Much of this article is drawn from the report Tatueringar och Hälsa (in Swedish) published by the Institute of Environmental Medicine at Karolinska Institutet.
Puzzling tattoos
The world’s oldest securely identified tattoos belong to Ötzi, the approximately 5,300-year-old mummified man discovered in the Alps in 1991. Ötzi has 61 tattoos consisting of lines or crosses on areas including his back, wrist (pictured) and calves. They were created by rubbing finely ground charcoal into small cuts in the skin. Researchers have debated the purpose of the tattoos, with one theory suggesting that they may have served a medicinal function. This is supported, among other things, by the fact that several of them are located close to areas where Ötzi showed signs of wear and injury.
Source: South Tyrol Museum of Archaeology.
