Laser Tattoo Removal

Etiology

Tattoos may occur for various reasons, including traumatic implantation of debris within the skin, a blast injury, iatrogenic pigment impregnation into soft tissue, and dental amalgam tattooing. However, the most common source of a tattoo is elective placement with a needle or tattoo gun.[7] Determining the etiology of the tattoo in question, as the mechanism of pigment implantation, will provide a clue regarding its histological depth and inform the plan for removing it, which is essential. Traumatic tattoos caused by explosions, such as with fireworks or gunpowder, can result in combustible material being embedded in the skin; great care should be taken in these circumstances since the application of the laser can ignite these particles and result in small explosions that endanger the patient and the laser operator.

While not as potentially dangerous as traumatic tattoos, elective tattoos may also provide surprises for the patient and the laser operator; many inks used in tattooing are combinations of multiple pigments, some more responsive to laser treatments than others. In these cases, treating the tattoo may cause it to change colors or only lighten slightly rather than fading to a noticeable extent. Some inks contain ferric oxide or titanium dioxide, which may undergo chemical reduction if heated by a laser, thus paradoxically darkening a treated tattoo.[8]

Epidemiology

Over the years, tattoos have become increasingly popular. According to a 2016 Harris Poll, 3 in 10 adults in the United States have at least 1 tattoo, compared to 2 in 10 adults in 2012, and a 2023 Pew Research survey (Pew survey) saw a further increase to 32%, with 22% of Americans having more than 1 tattoo. The Pew study reported that 38% of women and 27% of men in the United States have tattoos, with over half of women in the 18 to 49 age group having at least 1. In general, younger people are more likely to have tattoos, with over 40% of Americans in the 18 to 49 age group reporting 1 or more tattoos, but only 13% in those aged 65 and older.

Tattoos are most common in the Black population, with a 39% prevalence, and least common among those in the Asian population, with a 14% prevalence. Hispanic and White individuals are in the middle, with prevalences of 35% and 32%, respectively. There appear to be other demographic correlations with tattoos; 24% of college graduates and 21% of those with a graduate degree have tattoos, but 37% of individuals who did not complete college have tattoos. Tattooing is more common among lower-income adults (43%) and less common among high earners (21%). Tattoos are more common in individuals who do not consider themselves religious (41%) than those who do (29%). Lastly, 31% of heterosexual individuals in the United States have at least one tattoo, while 51% of gay, lesbian, and bisexual Americans do, with 68% of homosexual women reporting tattoos.

Individuals who smoke cigarettes are twice as likely to have tattoos than people who do not, and people who have reported having a history of alcohol or drug abuse are also twice as likely to have tattoos as those without such a history. On the other hand, there are no discernable relationships between liberal and conservative political views, urban versus suburban or rural living, and having served in the armed services or not with the presence of tattoos. Perhaps most importantly, 24% of individuals with tattoos regret the decision. Rates of regret are highest in Hispanic individuals (30%) and those without a college degree (25%). Eleven percent of individuals with tattoos have had or plan to undergo tattoo removal. Over 52,000 tattoo removal procedures were performed in the United States in 2018 alone.

Pathophysiology

Amateur tattoos are more superficially in the papillary dermis, whereas professional tattoos are located deeper in the reticular dermis. This fact often makes the removal of amateur tattoos easier than professional tattoos. Professional tattoos are also likely to be more elaborate, with multiple different pigments that may complicate removal by laser. While immune system action on tattoo particles begins the moment the pigment is placed into the skin, the comparatively large size of the ink particles, up to 970 nm, makes processing by white blood cells very challenging.[9]

Laser tattoo removal breaks down the pigment particles through photothermal (heat) and photomechanical (shockwave due to thermal expansion) effects. The resulting smaller particles can then be eliminated via phagocytosis by macrophages.[10] In some cases, however, macrophages may initiate an immune response that leads to a hypersensitivity reaction manifesting as erythema, edema, pruritus, urticaria, or even anaphylaxis.[11]

History and Physical

A thorough history is important to gather information about the tattoo to be treated and the patient receiving the treatment. Important points regarding the tattoo include its age and whether it is a "cover-up" layer or a "double" tattoo. Older tattoos have already undergone some degradation due to ultraviolet light exposure and may require fewer treatments to remove. Double tattoos, on the other hand, have more pigment deposited in the dermis, which means that an unexpectedly large proportion of the energy may be absorbed by the laser's chromophore, potentially resulting in burns and scarring. Tattoos that have been treated previously but have changed color or darkened may require more treatments than might otherwise be expected and may not be able to be removed completely.

Concerning the patient's medical history, it is important to know whether or not the patient has had prior tattoo removal and, if so, whether there were any complications. Additionally, any history of wound-healing difficulties, hypertrophic scarring, or keloids should be elicited. If there is a history of herpes simplex outbreaks, particularly in the context of facial tattoo removal, prophylactic antiviral medications should be provided.[12] Lastly, a medication history should be taken.[13][14]

The physical examination should note each of the different colors of the tattoo, as more intricate and colorful tattoos—particularly those with orange, yellow, and white pigments (often found in pink and light blue inks)—are more difficult to remove. Identifying the colors that are present will inform the selection of the appropriate laser. Determining the age of the tattoo and how faded it is will also provide some prognostic information about the number of treatments likely to be required for removal. Most important, however, is noting the patient's skin color. Typically recorded using the Fitzpatrick scale, the amount of pigmentation in the patient's skin will determine the risk of post-treatment dyspigmentation and, therefore, which laser is likely to be safest (see Table. Fitzpatrick Skin Types, Table) as darker skin is more prone to hypo- or hyperpigmentation after exposure to laser energy.[15]

Evaluation

Patients should be counseled that tattoo removal takes anywhere from 4 to 15 treatments depending on the age, color, quality, and mechanism of tattoo placement. Also, discuss the importance of sun avoidance pre- and post-treatment due to the risk of dyspigmentation. Photographs and written informed consent should be obtained initially, before every session, and after the treatment. The risks of the procedure should be discussed, which can include the following:

• Pain
• Bleeding
• Infection
• Loss of or damage to vision
• Damage to surrounding anatomy
• Need for additional procedures
• Hyperpigmentation
• Hypopigmentation
• Burning
• Blistering
• Scarring
• Skin texture change
• Unpredictable treatment response
• Color change within the tattoo, including paradoxical darkening
• Dissatisfaction with the outcome

While it is only an estimate, the Kirby Desai scale provides a means of estimating the number of treatments that will be required to clear the tattoo. The scale assigns points for the tattoo's location, with the head and neck being optimal and the distal extremity more challenging, the coloration, with black ink only being preferable to multicolored tattoos, the amount of ink, with superficial, amateur tattoos most favorable, and the amount of scarring and ink layering present, with less being better in both categories.[16]

Treatment / Management

The patient’s skin should be prepped with alcohol or chlorhexidine. Due to the fire risk, alcohol should be completely dry before beginning the procedure. Because laser treatments tend to be painful, the area in question may be anesthetized preoperatively with topical anesthetic cream (2.5% lidocaine-2.5% prilocaine or similar) or injection with a local anesthetic agent (2% lidocaine, 1% bupivacaine or similar) to produce either a regional block or anesthesia of the tattoo itself. If a topical anesthetic is used, it should be placed under an occlusive dressing for 45 to 60 minutes and then completely removed before starting treatment.

Before using the laser, it is critical to follow certain precautions. Everyone must wear safety glasses or goggles rated for the laser wavelength during treatment. Depending on where the tattoo is located, the patient may wear an identical pair of glasses or goggles to those the healthcare team members are using, or if the tattoo is near the eyes, metal eye shields or corneal protectors may be more practical. If there are windows in the treatment room, they should be shuttered to prevent the laser light from escaping and causing an injury via direct eye exposure or reflection of the laser light. The laser most dangerous to the human eye is the neodymium-doped yttrium-aluminum-garnet (Nd:YAG) laser because its long wavelength and affinity for melanin make it capable of reaching through the eye, all the way back to the melanocytes within the retina. Ideally, laser-safe masks should be worn by the healthcare team members to prevent inhalation of aerosolized epithelial particles as well.

For the first session, a "test patch" may be performed. This involves firing the laser at a single, small spot on the tattoo to determine how it responds to treatment at specific settings; test patches are most commonly employed when the patient has dark skin, a history of exuberant scarring, or if there is a concern that treating the tattoo with the laser will result in paradoxical color change.[17] A full treatment may be scheduled if the test patch does not exhibit any undesirable developments after 2 to 4 weeks.

The machines used for laser tattoo removal typically default to recommended settings for starting treatment, and these settings can generally be used very safely, if not always very effectively, due to their conservative fluences. Fluence is the energy density deposited by the laser into the tissue in 1 pulse, measured in J/cm². The fluence must be frequently increased above the default setting to produce a clinically significant effect. As the tattoo lightens with subsequent treatments, the fluence may need to be increased because of the lower availability of chromophores to absorb the laser energy. For QS lasers, such as the ruby and Nd:YAG lasers, fluences of 4 to 8 J/cm² and 6 to 12 J/cm² may be appropriate, but picosecond lasers will typically require lower fluence levels to achieve the same effect, such as 1 to 2 J/cm² for the picosecond alexandrite laser.[18][19]

With ruby, alexandrite, Nd:YAG, and frequency-doubled Nd:YAG (also known as potassium-titanyl-phosphate [KTP] because of the additional crystal used) lasers available for tattoo removal, selecting the most appropriate one for an individual patient's tattoo colors and skin pigmentation may be challenging. The alexandrite and ruby lasers emit deep, red-colored beams (755 nm and 694 nm, respectively), while the KTP laser is green (532 nm), and the Nd:YAG laser operates in the near infra-red range (1064 nm). As a general rule, tattoos are not treated effectively with lasers that produce light of the same color as the ink because that is the color reflected most efficiently by the pigment; for example, a ruby laser is liable to have little impact on a red tattoo, but treatment with a KTP laser would likely be successful. The ruby laser is best for blue, green, and purple pigments, the alexandrite for blue and green, the Nd:YAG for blue and green, and the KTP laser for red, yellow, brown, and orange. Because black pigment absorbs a broad spectrum of light wavelengths, the ruby, alexandrite, and 1064 nm Nd:YAG lasers can be effective for removing black tattoos, or even for tattoos that have undergone paradoxical darkening, although these tattoos may not clear completely even with a great many treatments (see Table. Type of Lasers for Tattoo Removal, Table).[20][21][22]

When firing the laser, the spots should overlap by 10% to 20%, and the most practical spot size for the tattoo being treated should be used. Larger spot sizes not only permit faster treatment of the tattoo but also reduce the relative amount of energy lost to diffraction within the skin, which occurs predominantly around the perimeter of the spot, hence the need for overlapping.[23][24] Cooling with cold air blown across the tattoo or periodic application of cold packs to the treated area will reduce patient discomfort and swelling.

Appropriate settings on the laser will result in immediate "frosting" of the tattoo during treatment, which represents the formation of gas bubbles in the skin; the lowest fluence that produces this reaction should be used to reduce thermal injury to the skin (see Image. Q-switched Alexandrite Laser). The white discoloration will typically clear within 20 minutes, permitting observation of any color change within the tattoo. Titrating laser settings to this clinical endpoint, as the extent of tattoo pigment reduction is not clinically apparent initially, and additional lightening will occur over the ensuing weeks as the degraded pigment particles are phagocytosed and cleared, is essential. If pinpoint bleeding or tissue spatter occurs, the fluence should be lowered immediately, as these are signs of excessive energy delivery.

Typically, laser sessions are repeated every 6 to 8 weeks, as tolerated, until the tattoo is completely cleared, no further progress is being made, or the patient elects to discontinue treatment. To expedite tattoo clearance, however, some protocols permit multiple treatment passes to be made in the same session. In 2012, Kossida et al developed the "R20" method, which involves repeating the treatment up to 4 times at 20-minute intervals, thereby allowing the frosting to clear between passes.[25] The "R0" method, described the following year by Reddy et al, permits multiple passes without waiting periods between them via the use of topical perfluorodecalin to clear the gas bubbles in the tissue twice as rapidly as when they are allowed to clear spontaneously (see Image. R0 Protocol With Q-switched Nd:YAG Laser).[26]

In contrast to the ruby, alexandrite, KTP, and Nd:YAG lasers, which are considered non-ablative, some authors advocate the use of fractionated ablative lasers, such as carbon dioxide and erbium-doped yttrium-aluminum-garnet (Er:YAG) lasers, to remove superficial pigment, like traumatic and amateur tattoos, either alone or in combination with non-ablative lasers.[27][28] Ablative lasers vaporize the epidermis and superficial dermis by targeting water as their chromophore, thereby permitting the pigment particles to be cleared during the healing process. Ablative lasers have also shown promise for treating refractory tattoos, such as those with light-colored ink or those that have undergone paradoxical darkening.[29] These lasers are typically avoided for treating patients with dark skin, however, particularly if energy is delivered with a continuous wave rather than via a fractionated system.(B3)

Differential Diagnosis

Numerous lasers are available to remove different colors of tattoo ink, but other nonselective tattoo removal methods are also available. Ablative options, such as carbon dioxide and Er:YAG lasers, can be used for superficial or recalcitrant tattoos. Dermabrasion, either manual or with powered instrumentation, may be used similarly to ablative lasers. At the same time, liquid nitrogen and chemical peeling agents, such as trichloroacetic acid, are less precisely applied and are therefore less commonly employed. Tattoos may also be excised surgically, although doing so exchanges a tattoo for a scar, and excising large sections of skin to remove more extensive tattoos is often not feasible.

Prognosis

The efficacy of laser tattoo removal depends on several factors—most importantly, the color of the ink, the color of the patient's skin, and the wavelength and pulse duration of the laser being used. Carbon-based black tattoos in fair-skinned individuals treated with QS ruby, QS alexandrite, or QS Nd:YAG lasers have more than a 90% chance of clearance and a low incidence of complications.[30] For darker-skinned patients, the QS Nd:YAG laser is the modality of choice, although the QS alexandrite laser is also safe and effective.[31][32] 

The ruby laser, on the other hand, poses a higher risk of hypopigmentation in these patients.[33] Newer technologies, such as picosecond lasers, are likely even safer for darker-skinned patients (Fitzpatrick type IV-VI) and seem to be both more effective and more comfortable than QS lasers for pain during and after treatment (see Image. Picosecond Alexandrite Tattoo Removal Results).[34][35][36] Overall, rates of complete tattoo clearance are in the 50% range (see Image. Tattoo Removal, Before and After).[31][35]

Complications

The most likely complication of laser tattoo removal is a requirement for more treatments than originally anticipated or unsatisfactory clearing of the tattoo, which may include residual pigment, a change in color or darkening, or a persistent outline of the artwork. Long-term or permanent skin changes may also occur, including alterations in texture and color. Hyperpigmentation is more common than hypopigmentation, although hypopigmentation is more likely to be permanent. Hyperpigmentation is treated with topical bleaching agents, such as 4% hydroquinone cream, while hypopigmentation may be treated with steroids to reduce the causative inflammation or with exposure to blue or ultraviolet light to stimulate melanin production.[37] Poor wound healing, such as blistering, infection, and scarring may occur, as can infection, although this is not common. If the settings employed are too aggressive, burning, skin sloughing, and scarring may result.