When explaining tattoo removal, the first thing we need to look at is not “How many sessions will it take?” but “Where is the ink located inside the skin?”

From the outside, a tattoo may look like a drawing placed on top of the skin.

But in reality, the ink particles are not simply sitting on the skin surface. They are embedded deeper inside the dermis.

That is why laser tattoo removal is not a procedure that peels off the outer skin surface.

It is closer to a process where laser energy breaks the ink particles trapped inside the skin into smaller fragments, and then the body slowly clears those fragments over time.

To put it simply, the laser does not erase the ink like rubbing it away with an eraser. Instead, it breaks larger ink particles into smaller pieces so the body can process them more easily.

Today, I’ll explain how laser tattoo removal works, why picosecond lasers are often mentioned in tattoo removal, and what has been reported in actual research, in a way that is easier to understand. :)

If you look at the image above, tattoo ink is not only located in the epidermis. It sits like dark particles inside the dermis.

From the body’s perspective, these ink particles are foreign materials.

However, when the particles are too large or remain stably embedded inside the dermis, the body cannot easily clear them, so they can stay for a long time.

This is why tattoos can remain visible for years or even decades.

The laser delivers strong energy to these ink particles within a very short period of time, and the ink particles receive an instant shock, breaking into smaller fragments.

After that, immune cells such as macrophages gradually process those smaller fragments, and over time, the tattoo color slowly fades.

So tattoo removal is not completed on the day of the procedure.

The laser breaks the ink quickly, but the body needs time to clear the broken particles.

The reason we leave several weeks between tattoo removal sessions is not only to let the skin rest.

It is also to allow time for skin recovery and for the fragmented ink to be processed by the body.

In tattoo removal, you often hear about nanosecond lasers and picosecond lasers. The key difference is how long the laser energy stays in the skin.

Nanosecond lasers use short pulses measured in nanoseconds, while picosecond lasers use even shorter pulses measured in picoseconds.

This may sound complicated, but here is an easier way to understand it.

If a nanosecond laser breaks ink particles into relatively larger fragments, a picosecond laser uses a shorter and stronger shock to break the ink into even finer fragments.

Of course, in actual skin, both thermal effects and mechanical shock effects occur together.

However, when explaining picosecond lasers in tattoo removal, the concept of the photomechanical effect is important. This means breaking pigment particles into smaller pieces through mechanical shock.

The finer the ink particles become, the easier they may be for the body to process.

In a study by Lee et al., the authors also explained that a 755 nm picosecond alexandrite laser may help selectively target pigment particles while reducing damage to the surrounding skin tissue.

This paper was published as a Brief Communication in Annals of Dermatology.

What makes this paper interesting is that it does not only include before-and-after photos. It also includes electron microscopy images.

If you look at the electron microscopy image above, it shows how pigment particles changed when comparing a picosecond laser and a nanosecond laser.

According to the paper, when treated with the 755 nm picosecond alexandrite laser, intracellular particles disappeared or were broken into smaller fragments, while surrounding cell damage was relatively minimal.

On the other hand, when treated with the 1064 nm nanosecond Nd:YAG laser, the number and size of particles decreased, but some changes suggesting cell damage, such as partial cell wall damage and vacuole formation, were observed.

This part is important when explaining the principle of tattoo removal.

Tattoo removal is not simply about burning the skin with a strong laser.

The ink particles need to be broken down sufficiently, while damage to the surrounding skin should be minimized as much as possible.

That is why tattoo removal is not just about laser strength. It is a process of continuously adjusting wavelength, pulse duration, energy, spot size, treatment intervals, and skin response.

What makes this paper interesting is that it does not only include before-and-after photos. It also includes electron microscopy images.

If you look at the electron microscopy image above, it shows how pigment particles changed when comparing a picosecond laser and a nanosecond laser.

According to the paper, when treated with the 755 nm picosecond alexandrite laser, intracellular particles disappeared or were broken into smaller fragments, while surrounding cell damage was relatively minimal.

On the other hand, when treated with the 1064 nm nanosecond Nd:YAG laser, the number and size of particles decreased, but some changes suggesting cell damage, such as partial cell wall damage and vacuole formation, were observed.

This part is important when explaining the principle of tattoo removal.

Tattoo removal is not simply about burning the skin with a strong laser.

The ink particles need to be broken down sufficiently, while damage to the surrounding skin should be minimized as much as possible.

That is why tattoo removal is not just about laser strength. It is a process of continuously adjusting wavelength, pulse duration, energy, spot size, treatment intervals, and skin response.

The difficulty of tattoo removal is not only about color.

It also matters how deeply the ink was placed, how dense the ink is, whether the tattoo was done once or layered multiple times, and whether it includes a cover-up.

A tattoo with shallow and light ink may respond relatively quickly.

On the other hand, tattoos with deep and dense ink are difficult to break down sufficiently in one session. Also, tattoos are not always placed evenly in a single layer; the depth can vary depending on the area.

Some parts may be shallow, some may be deep, and some areas may have clumped ink.

That is why tattoo removal is not a procedure where the same setting is simply repeated every time.

We need to observe the initial response, see how the skin recovers, check how much the color has faded, and evaluate the remaining tone before adjusting the wavelength, energy, and treatment interval again.

So, what did the actual study show?

In the study by Lee et al., tattoo removal using a 755 nm picosecond alexandrite laser was reported in six Korean patients with Fitzpatrick skin type IV.

The tattoos included black or red tattoos, and treatments were performed at one-month intervals using a 755 nm picosecond alexandrite laser.

The study evaluated tattoo clearance using photographs and graded the degree of removal from 0 to 3.

A score of 0 meant 0–25% clearance, 1 meant 25–50% clearance, 2 meant 50–75% clearance, and 3 meant 75–100% clearance.

If you look at the before-and-after photos above, the tattoo ink appears dark before treatment, and the color becomes lighter after treatment.

The paper reported that after 1 to 5 sessions of picosecond laser treatment, more than 75% clearance was observed in almost all treated tattoos.

The paper also mentioned that conventional nanosecond laser tattoo removal is known to require an average of around 8 to 9 sessions, while this study suggested that picosecond lasers may achieve a similar removal effect with fewer sessions.

However, this point needs to be interpreted carefully.

This was not a large-scale clinical trial. It was a small report involving six Korean patients, published in the Brief Communication format.

So we should not say, based on this single paper, that “all tattoos disappear within 1 to 5 sessions.”

A more accurate interpretation is that this paper reports tattoo removal outcomes using a 755 nm picosecond alexandrite laser in Asian skin.

There is another important point as well.

In this paper, all patients experienced temporary erythema and crusting, and three out of six patients had post-inflammatory hypopigmentation remaining three months after the final treatment.

This is very important.

Fading the tattoo is important, but controlling the treatment so that the skin does not become lighter, darker, or scarred is often even more important.

That is why tattoo removal should be understood as a procedure that gradually reduces ink while minimizing skin damage, rather than simply trying to remove it as quickly as possible.