Tattoos look permanent because the ink settles into the skin. New research in PNAS shows the real story is stranger. Much of that pigment does not stay in the dermis. It travels into the lymphatic system then lodges in the lymph nodes and can quietly reshape how the immune system deals with vaccines.
A team from the Institute for Research in Biomedicine in Switzerland traced what happens in the body after tattooing. They tattooed mice and watched the drainage routes in real time. The pigment left the skin within minutes and moved through lymphatic vessels into the nearest lymph node. The pigment did not pass through harmlessly. Instead it triggered a months long inflammatory response that researchers described as persistent and immune altering.
Macrophages are the immune system’s frontline vacuum cleaners. They swallow invaders and debris and in this case tattoo pigments. The study found that macrophages capture most of the ink that reaches the lymph nodes. They then pass in large numbers. Many break apart. Others form oversized giant cells packed with pigment.
The team used electron microscopy to show ruptured membranes and blebbing and other hallmarks of cell breakdown. This raised a question. What does the immune system do when many of its own cells pass in a lymph node filled with a foreign material it cannot remove?
The draining lymph nodes swelled. Immune cells flooded the site. Pro inflammatory cytokines climbed and remained elevated up to two months after tattooing. The inflammation did not resolve quickly. The pigments did not disappear either. They accumulated and spread further into downstream lymph nodes.
Human biopsy samples from tattooed patients showed the same pattern. Pigment was embedded in macrophages and giant cells long after the tattoo healed.
The team then tested two vaccines in tattooed mice which included an mRNA COVID 19 injection and a UV inactivated influenza vaccine.
The results were not uniform.
The antibody response to the mRNA COVID 19 vaccine was weaker. The researchers found lower expression of the spike protein in macrophages inside pigment laden lymph nodes. The ink appeared to interfere with the machinery the mRNA vaccine relies on.
The opposite happened with the UV inactivated influenza vaccine. The antibody response was stronger. That vaccine type depends more on presenting whole virus particles to immune cells. The heightened inflammatory environment may have amplified the reaction.
This difference matters. It means tattoo ink does not universally weaken or strengthen immunity. It modulates it based on the biology of each vaccine platform.
Nearly one in five people have tattoos worldwide and more than one in three in the United States. Until now very few studies have examined what tattoo ink actually does once it enters the body. Regulation of pigments remains limited even though many contain industrial grade colorants originally designed for plastics or paints.
This research is not a call to panic. It is a call to understand that tattoo ink is biologically active and persistent. It does not sit still. It interacts with immune cells and can influence the key immune hubs responsible for filtering threats.
Future studies will need to determine what this means for human vaccination in real life. For now the evidence is clear. Tattooing is not simply cosmetic. It leaves a lasting immune footprint.
References
Capucetti A, Falivene J, Pizzichetti C, et al. Tattoo ink induces inflammation in the draining lymph node and alters the immune response to vaccination. Proceedings of the National Academy of Sciences. 2025. 122(48): e2510392122. doi:10.1073/pnas.2510392122