Tattoo ink VS Cosmetic tattoo Pigment
The difference between tattoo ink and cosmetic tattoo pigment :
ink is made with a lot bigger molecules and the body can not brake it down. That's why it last forever!
Where the pigments are made with a lot smaller molecules and your body is able to brake it down, and that's why it fades in years.
The problem is as we get older the skin changes. But tatoo ink still stays in the same place. so it Could end up with dropping brows.
here is the Microscope image of tattoo ink and white blood cells. which are a lot bigger and white blood cells are not able to break them.