As tattoos become increasingly mainstream, particularly among young adults, new research raises questions about their long-term effects on the immune system. 

A new study has found that tattoo ink doesn’t just stay in the skin; it quickly travels to the lymph nodes, where it can trigger persistent inflammation, kill immune cells, and even alter the body’s response to vaccines.

With more than 30 percent of Americans — and an even greater percentage of younger people — now sporting at least one tattoo, the findings highlight a significant public health question about the safety of substances injected into the body.

The study, published in the journal Proceedings of the National Academy of Sciences, used mice to track what happens to tattoo ink after it’s injected into the skin.

Researchers discovered that pigments from black, red, and green inks drained into nearby lymph nodes within minutes and continued to accumulate for up to two months. The buildup led to chronic inflammation and the death of macrophages, which are crucial immune cells responsible for clearing foreign substances.

“In this work, we have demonstrated that macrophages exposed to different ink concentrations undergo apoptotic cell death with all the tested inks,” the researchers wrote.

Most notably, the presence of ink in the lymphatic system had a direct impact on vaccine effectiveness. The study found that the antibody response to an mRNA COVID-19 vaccine was significantly weaker when the shot was administered in the same tattooed area. In contrast, the inflammation caused by the ink appeared to boost the response to a traditional influenza vaccine.

While these experiments were conducted in mice, the researchers noted that the way ink accumulates in lymph nodes mirrors what has been observed in humans. The study’s authors from the Università della Svizzera italiana in Bellinzona emphasized the need for more stringent regulation of tattoo inks, which currently face far less oversight than pharmaceuticals.

“This work represents the most extensive study to date regarding the effect of tattoo ink on the immune response and raises serious health concerns associated with the tattooing practice,” the researchers wrote. “Our work underscores the need for further research to inform public health policies and regulatory frameworks regarding the safety of tattoo inks.”

The new research adds to a growing body of evidence suggesting potential health risks associated with tattoos. A 2024 Swedish study involving nearly 12,000 people found that tattooed individuals had a 21-percent higher risk of developing malignant lymphoma compared to those without tattoos.

Similarly, a Danish study published in January linked large tattoos to a more than two-fold increased risk of both skin cancer and lymphoma.