Research indicates that tattoo ink can accumulate in lymph nodes, potentially disrupting the immune system and leading to permanent alterations in the body’s disease defense mechanisms.

This conclusion arises from a study involving mice, which revealed chronic inflammation in the lymph nodes of tattooed animals—nodes that were stained with ink—and modified antibody responses to vaccinations. Similarly, studies have shown inflammation and discoloration in the lymph nodes of individuals with tattoos, persisting for years after the tattoo was applied.

The findings suggest that tattoos could increase disease risk and highlight the necessity for further investigation. Santiago González from the University of Lugano, Switzerland, asserts, “When you get a tattoo, you are essentially injecting ink into your body. This affects not only the skin’s appearance but also the immune system. Chronic inflammation, over time, can deplete the immune system, increasing susceptibility to infections and certain cancers—many questions remain that require additional research.”

Tattoos are becoming increasingly popular worldwide, with approximately 30 to 40 percent of individuals in Europe and the United States sporting at least one tattoo. Though Gonzalez does not have a tattoo, he admires them as an art form, stating, “I think they’re visually appealing.” Nonetheless, the long-term health implications of tattooing—particularly concerning the immune system—are still not well understood.

Gonzalez noted that he and his team were conducting an unrelated investigation into inflammation in mice when they observed a “crazy inflammatory response” after applying small identifying tattoos. Curious, they decided to delve deeper.

The team utilized standard commercial inks in black, red, and green to mark 25 square millimeter patches on the hind legs of several mice. With specialized imaging technologies, they tracked the ink traveling through lymph vessels towards nearby lymph nodes almost immediately, often within minutes.

In these nodes, the researchers found that macrophages (immune cells that eliminate debris, pathogens, and dead cells) absorbed the ink, turned the nodes discolored, and initiated acute inflammation. Within approximately 24 hours, these macrophages would perish and release the ink, which would then be taken up by other macrophages, creating a continuous cycle of chronic inflammation that outlasted the healing of the tattoo site.

After two months, during which the tattoos remained, the mice still exhibited inflammatory markers in their lymph nodes that were up to five times higher than typical, Gonzalez reported.

To comprehend how this inflammation affected immune functioning, the researchers administered a vaccine directly into the tattooed skin. Notably, the tattooed mice demonstrated a markedly weaker antibody response to the COVID-19 mRNA vaccine compared to control mice, while showing a stronger response to the influenza vaccine.

Further analysis revealed that the lymph node macrophages from tattooed mice were filled with ink and struggled to capture the COVID-19 vaccine. For mRNA vaccines to be effective, they must be processed by macrophages. Conversely, the protein-based influenza vaccines triggered an enhanced antibody response, likely due to an increase in immune cells drawn to the tattoo site. “The response may vary based on the type of vaccine,” Gonzalez explained.

Lastly, the researchers investigated a limited number of lymph node biopsies from individuals who had tattoos near their lymph nodes. Two years post-tattoo application, the lymph nodes retained visible pigment, housed within the same type of macrophages observed in the mouse research. “Their lymph nodes were entirely filled with ink,” noted Gonzalez.

Crucially, he emphasized that even if individuals undergo tattoo removal, the ink is likely to persist in the lymph nodes for a lifetime. “You can eliminate ink from your skin, but the ink in your lymph nodes remains,” he stated.

The research findings illuminate the long-suspected link between tattoos and immune response. Christel Nielsen at Lund University, Sweden, indicated that her team had recently published findings that suggest individuals with tattoos have a heightened melanoma risk. She believes that the findings from Gonzalez’s team may be explained by increased inflammation in lymph nodes. “This study provides compelling proof that this is indeed the case,” she remarked, calling it a significant advancement in our understanding of the relationship between tattoos and disease.

For Michael Jurbdazian, this study conducted at the German Federal Institute for Risk Assessment in Berlin paints a clearer picture of how tattoo pigments interact with the immune system. However, he notes that results from mouse studies might not precisely mirror human outcomes, especially considering the differences between human and mouse skin. “The correlation with human health, particularly once healing is complete, necessitates more investigation,” he stated.