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Tattoos were once limited to the likes of sailors and circus performers, but they have since become mainstream. College students might pick a favorite design over spring break, while older adults might choose one to honor a romantic partner, a child, or a hobby. Many people love their tattoos, but some come to regret them. Relationships can sour, a design may lose its appeal, or an obvious tattoo may become a professional liability. For former gang members, tattoo removal can be life changing. For others, it can be an immense relief.

So, how does laser tattoo removal work?

First, let’s take a look at how tattoos are actually made. To create a tattoo, ink is injected into the inner layer of skin, called the dermis. While the outer layer of skin (the epidermis) is constantly shedding cells and replacing them with new cells, the dermis is quite stable. When the ink is first injected, the immune system recognizes the material as foreign and tries to remove it. However, most of the ink granules are too large for your immune cells to engulf, so they stay in place. Tattoos will fade over time as the ink granules break down, but they are designed to be permanent.

Tattoo inks, which are classified as cosmetics, are not regulated by the U.S. Food and Drug Administration and often contain heavy metals and other toxic ingredients. As tattoos have become more popular, a wider variety of ink colors have become available—including red, orange, yellow, light blue, and fluorescent options.

These new colors can behave unpredictably over time and in response to laser treatment. According to Seminars in Plastic Surgery, some inks contain zinc or titanium oxides, which turn black or gray in response to laser treatment. These tattoos can often still be removed, but they require more treatments. In contrast, black or dark blue tattoos made with conventional India ink tend to be much easier to remove with lasers. Brown and green tattoo inks also respond well to laser treatment, according to StatPearls.

Lasers were invented in 1960 and can deliver a narrow beam of concentrated light at a specific wavelength. For example, “ruby” lasers deliver red light with a wavelength of 695 nanometers. When tattoo inks absorb laser energy, they can heat and shatter into pieces that are small enough for immune cells to remove. The trick is not to damage too much of the surrounding tissue in the process.

So, how does laser tattoo removal work? In general, black materials absorb all colors of light, white materials reflect all colors of light, and red materials reflect red light and absorb other colors. Therefore, a ruby laser can be effective for heating and destroying black tattoo ink on a light-colored background, but a ruby laser would not be a good choice for destroying red tattoo ink. The skin’s natural pigment (melanin) can also absorb laser light, so laser tattoo removal is more challenging for people with darker skin. Highly pigmented skin is more likely to absorb laser energy and be damaged, which also leaves less laser energy to destroy the tattoo ink.

In 1968, a ruby laser was used to remove dark-colored tattoos from light-skinned human volunteers, according to the Journal of Surgical Research. Depending on the amount of laser energy used, the laser treatment could significantly reduce the amount of tattoo pigment, but it could also produce skin damage similar to second- and third-degree burns. This study used “Q-switched” lasers, which deliver 10- to 20-nanosecond pulses of laser energy. A nanosecond is one-billionth of a second, or 10-9 seconds. Earlier studies using millisecond-long pulses of laser energy resulted in more severe tissue damage. A millisecond is one-thousandth of a second, or 10-3 seconds. The newest lasers deliver picosecond-long pulses of light, which seem to offer even better results. A picosecond is 10-12 seconds, or one-trillionth of a second.

Experiments on tattooed rats are currently being used to find optimal treatment conditions, as the Medical Science Monitor reports.

In 1983, a ground-breaking study in Science detailed how to use laser technology to remove specific biomedical targets without affecting the surrounding tissue. This concept of “photothermolysis” allowed scientists to target tattoo pigments at specific wavelengths.

Now, we use Q-switched lasers at 532 nm and 1064 nm to remove blue and black pigment in darker skin types, since these wavelengths are not well absorbed by melanin. The 532-nm laser is also effective against red, orange, yellow, and brown pigment in lighter skin types. Lasers of 694 nm and 755 nm are used for black, blue, and green pigment in lighter skin types.

The same concept of photothermolysis (and often the same lasers) are used to treat spider veins, moles, birthmarks, sun spots, freckles, and tattoos.

While laser tattoo removal has come a long way and is continuing to advance, good results are not guaranteed. Multicolored tattoos—especially in darker skin types—can still pose a challenge. Laser tattoo removal is also a long process that is not covered by insurance. Lasers can only affect the outermost layer of pigment, and the immune system needs six to eight weeks to clear away the fractured ink particles before the next treatment session. Many clients require six to 10 sessions before they are ready to stop, with some clients needing 20 or more. Thus, the process can easily take over a year.

Tattoos can also be removed with surgery, which often leaves a significant scar for all but the smallest of tattoos. However, this is often the best option for people who have developed an allergic reaction to a tattoo, or whose tattoo involves an area that was directly impacted by fireworks or explosives (which may leave flammable fragments). For someone who hates their tattoo but is not opposed to a different tattoo in the same location, there are many talented tattoo artists who love to turn old tattoos into new treasures.

Are you interested in all things related to technology? We are, too. Check out Northrop Grumman career opportunities to see how you can participate in this fascinating time of discovery.

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