Tattoos Do Odd Things to the Immune System

When you stick ink-filled needles into your skin, your body’s defenders respond accordingly. Scientists aren’t sure if that’s good or bad for you.
By Katherine J. Wu | The Atlantic |

THE ATLANTIC - In 2018, I paid a man a couple hundred dollars to repeatedly jam several needles into the skin of my right wrist. I felt as if I were being attacked by a microscopic cavalry of crabs. Into every jab went black ink, eventually forming the shape of double quotation marks. It was my first tattoo, and likely not my last.

In the thousands of years that tattoos have been around, not much has changed. The practice still involves carving wounds into permanent, inked-in shapes that we find aesthetically pleasing. But much of tattooing remains mysterious: Scientists still aren’t sure what makes certain tattoos fade fast, why others stick around when they’re supposed to disappear, or how they react to light. One of the strangest and least-studied enigmas, though, is how tattoos survive at all. Our immune system is constantly doing its darndest to destroy them—and understanding why it fails could clue us in to one of our bodies’ most important functions, even when we leave the skin blank.

When a tattoo is stamped onto skin, the body considers it an assault. The skin is the immune system’s “first barrier,” and is heavily stocked with fast-acting defensive cells that can leap into action when it’s breached, says Juliet Morrison, a virologist at UC Riverside. Those cells’ prime directive is to suss out anything foreign and destroy it so the healing process can begin.



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