How Do Tattoos Work?
New research suggests that our bodies might have an intriguing way of handling tattoos—and the findings could eventually help us get better at removing them.
I love this article written by Rachel Feltman of Popular Science.
If you ask most people how tattoos work, they're likely to get it a little bit wrong. The most pervasive oversimplification is that tattoo needles inject ink into the skin, deep enough that it stays put. In fact, tattoo needles are more like the nib of a fountain pen than a syringe; the ink isn't shot down through the needle, but suspended at the end of it when an artist dips the tool into a well. Then, when the tip of the needle pierces a hole in the recipient's skin (both the epidermis and the dermis beneath it), capillary action—the same force that makes liquid creep up the sides of a straw—draws the ink down into the dermis.
That’s how the ink gets into your skin. But why does it stay there?
Scientists have known for a while that tattoos are made possible not by ink-saturated skin cells, but by immune cells called macrophages. These white blood cells exist to gobble up foreign and cellular debris, and they come rushing whenever you're wounded. So it's not surprising that they show up when a needle keeps stabbing you and your skin keeps sucking up ink. The macrophages chow down, and their cellular membranes keep your tattoo ink nice and cozy for years to come.
In other words, your tattoo isn’t just the remnant of a battle between your proclivity for body art and your immune system. It’s a war that never stops.
Of course, tattoos aren't actually forever. They do fade away in time. Sunlight is anecdotally known to leach the color out of tattoos, but the study authors think macrophage turnover they discovered could also play a role.
The team thinks their results could eventually lead to more effective tattoo removal, though the exact mechanisms are still a little vague. Laser removal works by blasting those macrophages full of ink into smaller chunks, such that the lymphatic system drains them away like it does all the tiny bits of waste in your body. But it takes several sessions to clear everything away, and some tattoos only fade instead of disappearing. The researchers argue that this could be due to new macrophages swooping in to protect you from the larger of the remaining ink chunks, inadvertently protecting those ink chunks from you. If the tattoo removal process involved temporarily killing off or removing macrophages in the area with the use of certain antibodies, they say, the whole thing could theoretically be taken care of more quickly.
