A new study in mice reveals that tattoo ink can lead to chronic inflammation in lymph nodes, potentially altering immune responses for life. Human samples show similar effects years after tattooing. Researchers urge more investigation into health risks.
Scientists have uncovered evidence that tattooing injects ink deep into the body, triggering prolonged immune system changes. In a study published in PNAS, researchers led by Santiago González at the University of Lugano in Switzerland tattooed mice with standard commercial inks in black, red, and green on a 25-square-millimetre patch of skin on their hind feet.
Imaging showed the ink traveling via lymphatic vessels to nearby lymph nodes within minutes. There, immune cells called macrophages absorbed the ink, causing acute inflammation. This led to a cycle: the macrophages died, released the ink, and new ones took it up, sustaining chronic inflammation. Two months post-tattooing, inflammatory markers in the nodes were up to five times higher than normal.
The inflammation impacted vaccine responses. When vaccines were injected into the tattooed skin, mice showed a weaker antibody response to a covid-19 mRNA vaccine—likely because ink-filled macrophages processed it less effectively—but a stronger response to an influenza vaccine, possibly due to recruited immune cells. "It may really depend on the type of vaccine," González said.
Human lymph node biopsies from tattooed individuals, taken up to two years after, contained visible ink in macrophages, indicating lifelong retention. "You can eliminate the ink from the skin, but you can’t eliminate it from the lymph nodes," González noted. He warned that long-term inflammation could exhaust the immune system, raising risks of infections or cancers.
With 30 to 40 percent of people in Europe and the US having tattoos, experts like Christel Nielsen at Lund University see links to higher melanoma risks, calling this "a substantial advancement." However, Michael Giulbudagian at the German Federal Institute for Risk Assessment cautions that mouse results may not fully translate to humans due to skin differences, stressing further research.