Why Are Tattoos Permanent?
Ink is not quite permanent, but close to it. Tattoos can be removed through a few different methods, the best being the recently developed laser technology that heats the ink selectively so that it is absorbed in the body. Still, a course of laser treatments take time – months to more than a year. On their own, tattoos fade slowly over time. Yet the design remains clearly recognizable, though perhaps unattractive, after decades.
The slow fade raises an interesting question. If the cells of our skin are replaced regularly, why do tattoos persist indefinitely?
The cells in the epidermis, the outer skin layers, constantly replace themselves. This process is called exfoliation. The deeper layers of skin, the dermis, do not turnover and replace themselves. A foreign substance, i.e. tattoo ink, that is implanted in the dermis will remain for a very long time.
Foreign substances in the dermis are normally scooped up by white blood cells which carry them away. But tattoo pigment is made of particles that are too large to be ingested by white bloods cells.
Tattoo-removing lasers work by pulverizing ink into microfine particles. The ink particles are then small enough to be taken in by white blood cells and carried away.