What Happens to Tattoo Inks over a Long Period of Time?

A study was performed on how the skin of mice removes inks from tattoos. Both mice and humans have ‘clean-up cells’ called macrophages. Human macrophages work more slowly than mouse macrophages and appear to ‘hold on’ to tattoo ink for a much longer period of time.

https://www.sciencenews.org/article/inked-mice-hint-how-tattoos-persist-people