LONDON: Tattoos last forever – because the human body thinks it is under attack when someone draws on it.
The body’s complex processes, that keep our skin free from infection, are the same ones that allow ink to live forever in our skin.
It should be very difficult for anything to stay in the skin: humans shed about 40 000 skin cells per hour, or about 1 million per day. Anything drawn on to the skin would gradually flake or get washed off.
But tattoos are done using guns to punch through the outer layer of skin and into the dermis, which is the deeper layer of skin that doesn’t flake off. They do that by pushing in small needles over and over, quickly, pushing the ink deep into the fibres and nerves of the dermis.
Pushing so far into the skin is essentially a wound, and the body reacts as you’d expect it to. The immune system reacts to what it considers to be an attack by sending cells to the wound to start repairing the skin – that process might sound traumatic, but it’s actually what allows tattoos to stick around for so long.
The cells, known as macrophages, travel to the site of the wound and start eating up the ink that has been deposited there. Other cells and parts of the skin, such as fibroblasts, suck up the tattoo ink.
But they can’t do anything with it, and so it stays stuck in that layer, visible through the skin. Some of the ink will go into the upper layer of the skin and that will then be shed as normal. That’s why the process of getting a tattoo also includes time to let your skin heal, with the body taking two to four weeks to initially heal.
The body also keeps fighting the foreign ink throughout its owner’s life. That means that tattoos will gradually fade over time, a process that is also sped up by other things like light from the sun.
But the body can also be helped to get rid of the apparently permanent ink. Tattoos can be destroyed by lasers that reach deep into the skin, breaking the bits of ink into smaller particles that can be carried away more easily by those macrophages. – The Independent