Your Tattoo is INSIDE Your Immune System. Literally

Your Tattoo is INSIDE Your Immune System. Literally

The Incredible Drama Unfolding Under Your Skin

When you get a new tattoo, you’re not just decorating the surface of your skin – you’re kicking off an incredible drama deep within your body’s immune system. With each tasteful piece of body art, you set off a chain reaction involving millions of cells, grand sacrifices, and your immune system stepping in to protect you from yourself.

Let’s take a closer look at what’s really happening under your skin when you get a tattoo.

The Conveyor Belt of Death

Your skin has a huge job to do – it’s your largest organ and has the most direct contact with the outside world. Trillions of microbes, dirt, insects, and other potential threats can’t be allowed to get inside you. But at the same time, your skin is constantly being damaged as you move through the world.

Your body has a clever solution to this problem – your skin is essentially a “conveyor belt of death.” The part of your skin that you can see is actually made up of dead cells. The living, active part of your skin cells begins around one millimeter deep, in what’s known as the “skin industrial complex.”

More: You Are The Center of The Universe (Literally)

Stem cells in this deeper layer are constantly cloning themselves and producing new skin cells. These new cells begin a journey from the inside to the outside of your skin. As they mature, they interlock with each other and produce special structures called Lamellar bodies that squirt out fat to create a waterproof barrier. Then, the cells dry out and kill themselves, merging together into inseparable lumps.

This wall of dead cells is constantly being pushed upwards by new cells moving up from below. In fact, you shed around 200 million dead skin cells every hour, along with any dirt or bacteria that’s stuck to them. This conveyor belt of death is an effective way to protect your body, but it also means that getting a tattoo on the surface of your skin would be pretty much useless – the ink would just get shed along with the dead cells.

To get a tattoo that lasts, we need to go deeper.

The Immune System Strikes Back

Below the conveyor belt of death lies the dermis – a layer full of structural tissue, tiny blood vessels, sensory cells, hair roots, sweat glands, and of course, loads of immune cells guarding your flesh.

This is where the real action happens when you get a tattoo. Imagine the scene – half a dozen “monoliths” the size of skyscrapers (the tattoo needles) slam through the fifty layers of dead cells and deep into the dermis, ripping huge holes into the skin. This violent process kills tens of thousands of cells right away, tearing them to pieces or damaging them beyond repair.

Luckily, your tattoo artist has taken the proper precautions and disinfected their tools and your skin. But even with the best sterilization, you can never get rid of 100% of bacteria, and some survivors make it into your flesh.

Your immune system is not amused. All the death and destruction wakes up hundreds of thousands of macrophages – specialized immune cells in your dermis that rush in to defend you. They immediately start killing any bacteria, releasing chemicals to call for reinforcements, and ordering your blood vessels to open up and swell your dermis with fluid.

But the real problem isn’t just the wounds and invading bacteria – it’s the tidal wave of chemicals that floods your tissue. Tattoo ink can be made from hundreds of different substances, some of which may even be toxic or carcinogenic. Most inks contain heavy metals like lead, nickel, or chromium dissolved in distilled water.

This creates a chaotic battlefield – a mix of dead cell parts, panicked bacteria, blood, bodily fluids, platelets trying to close wounds, more and more immune cells rushing in, and of course, the flood of tattoo ink.

The Immune System’s Impossible Task

On the microscopic scale of your cells, the clumps of tattoo ink particles are absolutely massive – if you were the size of a cell, they’d range from the size of big dogs to small office buildings. Your immune system’s main job is to identify what is not “you” and smash it until it’s dead. The macrophages are desperately trying to do that with the tattoo ink.

Like tiny octopuses, they extend arm-like structures and begin pulling the ink particles inside. Usually, when a macrophage has eaten an enemy, it showers it in acid to dissolve it. But this doesn’t work with the tattoo ink. They try and try, but the ink particles don’t react in any way.

And this is just for the particles small enough to be devoured. The larger chunks are surrounded by thousands of your skin’s structural cells and macrophages, all nomming on them and bathing them in acid and attack chemicals, trying to destroy and kill them. But the ink still doesn’t budge.

Finally, your immune system has to concede defeat. It will not win this fight – so it does the next best thing: it doesn’t lose. Your cells don’t know how dangerous these metal and chemical ink particles are, but they can at least not let them spread around. So they just stay in place, vacuuming up as many ink particles as they can fit into their bodies and surrounding the larger ones, trapping them in the only “prison” they can build: themselves.

Bit by bit, the ink inside thousands of tiny wounds moves inside millions of your immune cells, which then freeze in place forever.

Your Tattoo is Now Part of Your Immune System

On the outside, you don’t notice any of this incredible drama unfolding. Your new tattoo looks fresh and the colors are vibrant. Your skin is irritated, swollen, and painful. But as the wounds heal and the tiny holes close up, the conveyor belt of death does its job, shedding the dead, ink-filled cells and replacing them with fresh, clean ones.

Your tattoo becomes a little less vibrant over time, as the ink is no longer sitting on the surface of your skin, but rather trapped deep inside it. But what you’re really seeing is millions of your macrophages, sitting patiently in your dermis and holding the ink in place, protecting your body from these foreign particles.

Your immune system is the reason your tattoo is forever.

Nothing Lasts Forever (Except Your Tattoo)

Of course, even this arrangement isn’t permanent. Over time, your macrophages will get old and die, and new ones will come in to gobble up the ink and keep it in place. But sometimes, a tiny bit of ink escapes. Most of it gets recaptured and locked back in, but not always in the exact same place.

This is why tattoos tend to fade and become less sharp and crisp at the edges over time – some of the ink has escaped the original tattoo and spread around. In fact, a small amount of tattoo ink often ends up escaping the tattoo entirely, riding fluids flowing from your tissue and spreading throughout your body.

This is another reason why it’s important for tattoo ink to be as non-toxic as possible – you don’t want these particles spreading poison around your body.

Your immune system also kind of doesn’t want you to remove tattoos. To do that, the ink is usually blasted with lasers, which heat up the particles until they break into smaller chunks. This process cooks your brave macrophages in the process. With each round of laser removal, more of the tattoo is broken down and carried away by fluids. But also, every time, new macrophages rush in to lock the remaining ink in place.

So if you’re thinking about getting a tattoo, or removing one, it’s worth considering the incredible struggle going on inside your skin and the sacrifice of your macrophage buddies. They’re working hard to keep that ink in place, just for you.

Appreciate Your Immune System

While tattoos may not be a huge deal for your body if applied correctly, it’s fascinating to understand the drama unfolding beneath the surface. Your immune system is working hard to protect you, even from the things you choose to put in your skin.

To really appreciate your amazing immune system, you have to know about it first. And the same goes for understanding anything going on in our universe. That’s why we’ve created a series of interactive lessons with our friends at Brilliant.org to help you take your scientific knowledge to the next level.

These lessons let you further explore the topics covered in our most popular videos, from rabies and mammalian metabolism to climate science and supernovae. Brilliant has thousands of lessons to choose from, and each one is interactive, like a one-on-one version of a Kurzgesagt video.

Brilliant’s latest course, “How LLMs Work,” takes you under the hood of real language models. It demystifies technologies like ChatGPT, with interactive lessons on everything from how models build vocabulary to how they choose their next word. You’ll learn how to tune LLMs to produce output with exactly the tonality you desire, whether it’s poetry or a cover letter. And you’ll understand why training is really everything, by comparing models trained on Taylor Swift lyrics and the legal speech of Big Tech’s Terms and Conditions.

This isn’t just another course – it’s an immersive AI workshop, allowing you to experience and harness the mechanics of today’s most advanced tools.

To get hands-on with Kurzgesagt lessons and explore everything Brilliant has to offer, you can start your free, 30-day trial by signing up at Brilliant.org/nutshell. There’s even an extra perk for Kurzgesagt viewers – the first 200 people to use the link get 20% off an annual membership once their trial ends.

We love seeing how the gears interlock with our research, and Brilliant gives you the tools to understand how everything fits together. So dive in, and let’s explore the incredible world beneath your skin – and beyond.