Some researchers are concerned that tattooing brings health risks

Olga Kolbakova / Alamy

Tattoo ink collects in lymph nodes and interferes with the immune system, causing potentially lifelong changes to the body’s disease-fighting mechanisms.

That is the conclusion of a study in mice, in which tattooed animals showed chronic inflammation in their lymph nodes – which were pigmented with the ink – and had altered antibody responses to vaccines. Human lymph nodes from tattooed individuals had similar inflammation and colouring, even years after people received their tattoos.

The findings suggest tattoos might be associated with higher disease risks and that additional research is needed, says Santiago González at the University of Lugano in Switzerland.

“When you’re tattooing, you’re actually injecting ink into your body,” he says. “It’s not just a cosmetic effect that’s associated with the skin; there are effects on the immune system as well. The problem is that, in the long term, inflammation ends up exhausting the immune system and then you have a higher chance of getting infections or some types of cancers. So there are a lot of open questions that need further study.”

Tattooing has become a global trend. Between 30 and 40 per cent of people in Europe and the US have at least one tattoo. González isn’t among them, although he appreciates tattoos as an art form. “I think that, aesthetically, they are beautiful,” he says. But scientists have relatively little information about long-term health effects of the tattooing process, especially in terms of how tattoos affect the immune system.

González says he and his colleagues were working on an unrelated research project on inflammation in mice when they realised that the animals developed “crazy inflammatory reactions” after being given small tattoos for identification. Intrigued, they decided to investigate further.

The researchers used standard commercial inks in black, red and green to tattoo a 25-square-millimetre patch of skin on the hind feet of dozens of mice. With specialised imaging equipment, they watched the ink travel along the lymphatic vessels inside the leg up to the nearby lymph nodes almost immediately, often within minutes.

There, the team saw that macrophages – immune cells that clean up debris, pathogens and dead cells – captured the ink, tinting the nodes and provoking acute inflammation. Within about 24 hours, those macrophages died, releasing the ink, which then got captured by other macrophages. Those, too, would die and release ink, which would get taken up by yet other macrophages – creating a cycle of prominent, chronic inflammation that lasted well after the tattoo site itself had healed.