Here’s something you probably haven’t given much thought to: Why do tattoos last forever?
這也許是你很少會思考的問題:為什么紋身能夠永久留在皮膚上呢?
The answer is more interesting than you might think, which is that your body thinks it is under attack when someone draws on it.
這個問題的答案也許比你想象的更有趣——你的身體在紋身過程中會認為它受到了襲擊。
It’s actually very difficult for anything to stay on the skin, The Independent reports. We shed about 40,000 skin cells per hour, or around a million per day. Anything drawn onto the skin — by a pen, for example — gradually flakes or gets washed off.
So how do tattoos avoid shedding? The answer is pretty simple — the gun (or other tool used to create the art) pushes the ink through the outer layer of the skin and into the dermis, which is a deeper layer of skin that doesn’t flake off. It’s composed of collagen fibers, nerves, blood glands, and more.
Every time a needle penetrates, it causes a wound. This alerts the body to begin the inflammatory process, which sends immune system cells that try to start repairing the skin — and while this sounds like a bad thing, it’s actually what makes the tattoo last.
The cells try to “eat” the ink and transfer it away from the dermis, but there is more ink than they can break down, so the artwork stays. This is also a window in how laser removal works — the laser breaks down the ink, allowing the cells, called macrophages, to transfer the ink away.