ZME readers, think twice before getting a tattoo.

Here’s a great idea for a tattoo: 沒有意義

Speaking of which, have you ever wondered what makes tattoos permanently engraved on the skin? Most people would answer it’s because the ink goes so deep inside your skin that it can’t get out. This isn’t the real reason why tattoos are permanent, though. Basically, from the first piece of the needle, your tattoo and your body’s immune system are locked in a tug that never stops. The secret to a permanent tattoo is, in fact, a permanent inflammation.

When a tattoo needle punctures the skin, it rips through the epidermis, the outer layer of skin, and spills ink in the dermis, the inner layer of skin which is flooded with blood vessels and nerves. With each penetration, the immune system is alerted there’s a wound going on and immune system cells are sent to the site. Some of these are macrophages which gobble up the ink in an attempt to clean the area. What’s left of the ink becomes absorbed by skin cells called fibroblasts. Most of the fibroblasts and macrophages alike become suspended in the dermis where they’re locked permanently. The dye in both cells shows through the body which is why you can see your tattoo in the first place.

For a more detailed and entertaining view, check out this TED talk embedded below: