The ink within your Tattoo tends to be made of compounds from heavy metals, such as lead, copper, and manganese. Some red inks even contain mercury.
The metals in the ink is what gives your tattoos their permanency, but some inks have been known to cause allergic reactions like eczema or scarring.
When the needle inserts this ink into your skin, the body's immune system recognises these particles as foreign intruders. This is when an army of white blood cells are dispatched, attempting to 'eat' the ink particles, which only the tiniest pieces of ink particles are eaten and off they go to the liver, and pooped out.. Pretty cool huh?