Tattoos have developed a varied form of expression across the world, but the science behind their everlasting-presence is even more fascinating. Ink flows down the needles when they pierce the epidermis. Once the ink is inside the skin, the body’s immune system can’t ingest it, leaving the tattoo to stay. Or the more science-y answer is this:
The reason tattoo ink stays in skin forever has to do with the immune system.
When you get a tattoo, the ink flows down the tattooing needle into the middle layer of your skin, called the dermis.
That creates a wound, which your body tries to heal by sending macrophages (a type of white blood cell) to the area.
The macrophages swallow the ink in an effort to take the foreign particle away from the wound.
But the pigment in the ink is too large for the macrophages to remove, so the macrophages — with the ink inside — end up stuck in the dermis.