One in four Swedes already adorns their bodies with tattoos, and this habit is even more common among young women. According to a recent survey by the Swedish Public Health Agency, 28% of women and 21% of men admitted to having at least one tattoo. While most people live with them peacefully, nearly five percent (4.7%) experience skin problems that can become a real headache over time. We’ve explored what exactly gets under the skin, where pigment particles go, and whether you should fear what you’re permanently applying to your body.
How Pigment Stays in the Dermis
A tattoo machine makes tens of thousands of punctures per minute and continuously supplies ink. The artist’s task is to deposit pigment particles into the middle layer of the skin, the dermis, about one to two millimeters below the surface. If the injection is too shallow, the design will simply wash away with the regenerating epidermis, and if it’s too deep, the outline will bleed and blur. When particles end up in the dermis, the immune system reacts: macrophages, the so-called “big eaters” of the immune system, engulf the pigment but cannot process it like bacteria. The dyes are too stable, so they remain inside the cells. When a macrophage dies, the pigment is released, and new cells pick it up. This initiates a slow local cycle of pigment transfer from one cell generation to the next. French researchers first vividly demonstrated this mechanism in a 2018 study on mice. “Most pigment particles remain within macrophages, passing from one cell generation to another,” explains Nanna Fjordqvist, an immunologist at the Institute of Environmental Medicine at the Karolinska Institute.
Pigment Reaches Lymph Nodes
However, the pigment-laden macrophages themselves begin to function differently. In a 2025 Swiss study, scientists tattooed the hind paw pads of mice—roughly the size of a palm by human standards—and observed immune reactions in real-time. Within ten minutes, pigment particles reached the nearest lymph nodes, triggering a noticeable immune response. A significant portion of the ink settled there, consistent with post-mortem observations in humans. However, some pigment traveled further, reaching the abdominal lymph nodes. “It’s important to understand where pigments ultimately settle. Do they stay in the first lymph nodes or continue to move through the body? In this mouse study, some particles moved further, but whether this applies to humans—we don’t know yet,” says Fjordqvist.
Particularly interesting is how tattoos affect vaccine responses. Mice with tattoos, after receiving an mRNA COVID-19 vaccine, developed a weaker antibody response than control animals. However, they responded more strongly to a different technology influenza vaccine. The conclusion: tattoos, at least in rodents, alter how the immune system responds to external stimuli.
What’s Inside Tattoo Ink and Why It’s Not Approved in Advance
The word “tattoo” itself comes from the Polynesian word “tatau,” meaning “to strike” or “to beat.” It was introduced into English by James Cook after his voyages in the Pacific Ocean in the 18th century, and from there, it spread to other languages. The composition of modern inks is not reassuring: black pigment often contains carbon black—the same material that protects car tires from UV radiation. Older inks were metal-based: cadmium provided yellow and orange hues, chromium green, mercury red, and cobalt blue. But metallic pigments are dull, so in recent decades, azo pigments with bright colors have dominated the market. The problem is that azo dyes can break down into carcinogenic substances. Plus, there are solvents, binders, preservatives, and other additives.
Since 2022, the EU has had the REACH regulation, which limits the level of toxic substances in tattoo inks, especially carcinogens, allergens, and substances affecting fertility. However, there is no system for pre-market approval of inks—no authority checks them before they reach the studio. “These chemicals were not originally designed for application to the skin or anywhere in the body,” emphasizes Ina Anveden Berglind, a dermatologist at the Center for Occupational and Environmental Medicine in Stockholm and a researcher at the Karolinska Institute. In 2024, the Swedish Medical Products Agency inspected studios in about a hundred municipalities and examined 445 tattoo inks. More than half did not comply with REACH labeling requirements, and in many cases, the ingredient list itself was incomplete. “When the labeling is so incomplete, even the most reputable studio cannot guarantee that the ink meets the standards,” notes Berglind.
Tattoos and Cancer Risk: What the Data Says
There has long been concern that tattoos increase the risk of lymphoma and skin cancer. Swedish scientists sent questionnaires to individuals in the national cancer registry with lymphoma and various types of skin cancer, as well as comparable control groups without a diagnosis. A statistical link was found: people with lymphoma or melanoma had tattoos slightly more often than control participants. No link was found for squamous cell carcinoma. However, this data needs to be interpreted with caution, according to Maria Feychting, a professor of epidemiology at the Karolinska Institute. The low response rate, the long period between tattooing and the questionnaire, and the lack of dose-dependency—large tattoos did not carry an increased risk. In the lymphoma study, the peak risk occurred in the years immediately after tattooing, which is unusual for a disease that develops over years. In the melanoma study, most tumors were located outside the tattooed area. A recent review of seven studies, including Swedish ones, concluded that there is no convincing evidence yet linking tattoos to skin cancer or lymphoma. “We are surrounded by carcinogenic substances, and they are also present in tattoo inks. But this doesn’t necessarily mean an increased cancer risk. We need more robust studies,” says Feychting. Such work is already underway.
What is Definitely Known About Skin Problems
Infections are a matter of studio hygiene, and the risk is low in a reputable establishment. However, skin reactions can be long-lasting, and choosing an artist is not a panacea. “People react differently to different substances in the ink,” reminds Berglind. The risk of long-term problems increases with tattoo size:
| Tattoo Size | Proportion with Skin Problems |
|---|---|
| Large (more than five palms) | 12% |
| Small | 2% |
Red pigment is a separate issue. Red tattoos are more likely to cause phototoxic reactions in the sun: itching, redness, swelling, and pain. In one study, over a fifth of tattooed individuals reported such reactions. If the tattoo is on the arms, neck, or legs, it’s difficult to hide it from the sun. Another bane is contact allergy to a component of the ink. The itching can be unbearable, and unlike the tattoo itself, the allergy doesn’t resolve on its own and is usually lifelong. Sometimes, the only solution is surgical removal, and for large areas, skin grafting. Laser removal can be harmful in cases of contact allergy: the laser breaks down the pigment into smaller particles that the immune system can more easily remove, but these particles can spread throughout the body and worsen the allergy. Steroid injections (often repeated) can help, or in the best cases, a cream with a JAK inhibitor—in a recent study, such treatment completely relieved itching in two patients.
“The substances that enter the body with a tattoo are not harmless. I would advise very careful consideration of tattoos and to remember that the risk of problems is higher with large, colored, and red designs. At the same time, I don’t lose sleep over tattoo risks: the desire to decorate the body is deeply ingrained in us; we’ve been doing it for thousands of years,” concludes Berglind.
A Millennia-Old Habit
The oldest reliably identified tattoos belong to Ötzi, a mummified man approximately 5,300 years old, found in the Alps in 1991. He had 61 tattoos on his body in the form of lines and crosses on his back, wrists, and calves, made by rubbing finely ground charcoal into skin incisions. Scientists still debate the purpose of these designs: one theory links them to a therapeutic function, especially since several tattoos are located near areas where Ötzi showed signs of wear and tear and injury. Thus, the practice of introducing pigment into the skin is not a recent decade-long fad but a practice that has accompanied humanity since deep antiquity. The only question is how well we understand what we are carrying under our skin.