Tattoo pigments do not remain confined to the skin but migrate through the body and accumulate in lymph nodes, influencing immune system function. This was shown in a mouse study published in the journal Proceedings of the National Academy of Sciences (PNAS).

The work challenges the notion of tattoos as a purely local intervention. Researchers demonstrated that insoluble ink particles, once introduced into the skin, enter the lymphatic system and are retained in lymph nodes, where they interact with immune cells.

The experiments were conducted on mice: black, red, and green tattoos were applied to the animals’ paw pads. Using highly sensitive microscopy, scientists traced the movement of the pigments and found that some particles reached the nearest lymph nodes within the first few hours. There, they were engulfed by macrophages—cells that play a key role in initiating immune responses.

Within 24 hours after tattooing, the number of macrophages in the lymph nodes dropped sharply, indicating that some of these cells died after contact with the ink. At the same time, the pigments themselves remained in the lymph nodes for at least two months. Their impact on immunity proved to be complex and situation-dependent.

When an mRNA COVID-19 vaccine was administered into a tattooed area, the immune response—antibody production—was weakened. By contrast, when an inactivated influenza vaccine was used, the local inflammation associated with macrophage death actually enhanced the immune response.

The authors emphasize that it is still too early to directly extrapolate these results to humans. However, they advise against administering vaccinations directly into tattooed areas and recommend greater caution overall, as the long-term effects of tattoo pigments on the immune system remain poorly understood.