Here's what really happens when you remove a tattoo with lasers

Laser tattoo removal might look simpler than getting inked, but it's actually a really complicated process that shouldn't be relied on as a casual solution to a permanent problem.

Here's how it works.

Tattoo inks tend to be made of compounds from heavy metals. According to this Smarter Every Day video, tattoo inks often contain metals like lead, copper, and manganese. Some red inks even contain mercury.

The metals in the ink is what gives tattoos their permanency, but some inks have been known to cause allergic reactions like eczema or substantial scarring.

From the moment a needle deposits ink deep in the skin, the immune system recognizes the these particles as foreign intruders, dispatching armies of white blood cells to engulf them. The white blood cells then escort small ink particles to the liver, where they are processed and excreted.

But many of the ink particles are much larger than white blood cells, which is why new tattoos fade over time, but won't completely disappear naturally.

You can see the size difference in the gif below. The black splotches are ink particles, which dwarf the blood cells swimming around them.

Even over time, as the white blood cells eat away at the ink particles, most are still too large for the white blood cells to grab onto and remove from the skin.

Patrick Lappert, a plastic surgeon who also does tattoo removal, tells Smarter Every Day that a white blood cell trying to engulf an ink particle would be like a human "taking a bite out of an elephant."

That's why they're permanent. To erase a tattoo, you need lasers to break up the ink particles.

Tattoo removal lasers, also called Q-switch lasers or ultra-short pulse lasers, are extremely hot, operate in a very narrow frequency, and are very, very fast. The tattoo removal laser in the video, called the PicoLaser, works on a scale of picoseconds, or a trillionth of a second.

This speed and heat is crucial to cracking the ink particles apart.

To break up an ink particle, you need to heat it to make it expand due to thermal expansion, but the zap has to be quick enough so that half of the particle remains cool. The opposing cool and hot forces then rip the ink particle apart.

This process, called photothermolysis, is also used in laser hair removal.

Once the lasers break the ink particles apart into bite-sized chunks, the white blood cells can absorb them for transportation to the liver.

Now this may sound relatively easy, but the expensive process of tattoo removal often takes several rounds of treatments and can leave scarring. Darker pigments are eliminated more easily while lighter and more reflective inks are less responsive to the lasers.

It's also quite painful, often more so than getting a tattoo in the first place. The lasers heat the ink particles to thousands of degrees, but it happens so rapidly and specifically directed toward the ink that the laser doesn't burn the tissue - the energy instead collapses into a shockwave. The shockwave vibrates through the skin and causes the upper layer of skin to lift up and appear white, or to "frost." Though painful, this effect usually lasts just a few seconds.

For some, the appeal of tattoos might be hard to deny. But when it comes to tattoo removal, it might be better to choose wisely and be sure about what you want before diving in front of the needle.

Watch the whole Smarter Every Day video about tattoo removal.