The Dangerous Effect of Tattoos on the Immune System

A groundbreaking study by a Swiss the research group led by Prof. Santiago F. González, published today in the prestigious journal Proceedings of the National Academy of Sciences (PNAS), raises new questions about the safety of tattoos. The study by the Institute for Research in Biomedicine, affiliated with USI, was conducted together with 12 international groups, who examined the toxicity of tattoo inks, focusing on the three most commonly used colors: black, red and green. One of the key findings is that tattoo ink not only remains in the skin but also accumulates in the immune system, where it stays associated with its cells for years. Moreover, the ink induces cell death and triggers a chronic inflammatory reaction that disrupts the normal function of the body’s defense system. This study opens the door to further research into the potential link between tattoos and health problems such as cancer or autoimmune diseases.

The researchers discovered that once a tattoo is made, the ink rapidly travels through the lymphatic system and, within hours, accumulates in large quantities in the lymph nodes — key organs of the body’s defense system. Inside these nodes, immune cells called macrophages actively capture all types of pigment. This ink uptake triggers an inflammatory response with two phases: an acute phase lasting about two days after tattooing, followed by a chronic phase that can persist for years. The chronic phase is particularly concerning because it weakens the immune system, potentially increasing the susceptibility to infections and cancer. The study also showed that macrophages cannot break down the ink like they would other pathogens, wich causes them to die, especially with red and black inks, suggesting these colors may be more toxic. As a result, ink remains trapped in the lymph nodes in a continuous cycle of capture and cell death, gradually affecting the immune system’s defensive capacity.

Finally, the research explored a question raised during the COVID-19 pandemic: could receiving a vaccine in a tattooed arm affect vaccine efficacy? The study found that tattooed mice produced significantly lower levels of antibodies after vaccination. This effect is likely due to the impaired function of immune cells that remain associated with tattoo ink for long periods. Similarly, human immune cells previously exposed to ink also showed a weakened response to vaccination.

These findings raise concerns about tattoo safety and highlight important questions: how might chronic inflammation caused by ink affect other diseases, such as cancer or autoimmune disorders? Further research will be essential to expand our knowledge in this area and to propose safer procedures for this increasingly common practice.