Pigment (Specific)

Carbon black

It is the basis of black pigments. Although it is a carbon powder and a simple substance, there are problems with particle size and PAHs (polycyclic aromatic hydrocarbons) when using it for permanent makeup.

Hearing about carbon powder, many medical professionals may think, “How about using medicinal charcoal?” Medicinal Carbon is listed in the Japanese Pharmacopoeia and is used for the purpose of absorbing drugs remaining in the gastrointestinal tract by being taken internally during drug intoxication.

However, there is the problem of particle size.

Although there are no restrictions on the particle size of medicinal charcoal, it is activated carbon considering its purpose. Activated carbon is a mass of carbon having a structure that has many pores and allows drugs to be incorporated therein, so it must have a certain size. The particle size is about 10 µm at the smallest. This size is rough and not suitable for fine line drawing of permanent makeup.

Therefore, instead of medicinal charcoal, it is necessary to look for carbon with a finer particle size. A diameter of about 10 nm is suitable for the purpose.

It is possible to search for a material with a small particle size from raw materials that are generally distributed, but if the amount is small, it is also possible to make by yourself. In fact, overseas medical papers sometimes describe the self-made method.

The method is to light oil or a candle and hold it over a metal plate to create soot. This is collected to make fine carbon powder, and it is often described in medical papers that color the cornea, which has become blind and cloudy, black with permanent makeup. It would be nice to know for reference how to make fine carbon powder.

Figure 6

 Making dyes for permanent makeup from soot. Created each time during surgery. Reproduction of the photograph in “Simple and novel technique of using lampblack soot as a corneal tattoo for disfiguring corneal opacities. Indian J Ophthalmol. Reprinted from 2021 Dec;69(12):3748-3751”

 Next is the problem of PAHs (polycyclic aromatic hydrocarbons). Let's get into the background of this issue.

PAHs is a generic term, and some of the compounds contained in PAHs are carcinogenic. PAHs are substances that are produced when organic matter is incompletely burned and are widely present in the natural world. However, there is a strong belief in Germany that industrial products, especially those that can be licked or chewed by infants, need to be strictly regulated. Since 2008, when receiving the GS mark (Germany's product safety certification), measurement of the content of typical carcinogenic PAHs has been required, and standard values ​​have been set.

After that, in 2022, the EU established regulations on pigments for permanent makeup, nine substances, i.e., naphthalene, benzo[a]pyrene, benzo[e]pyrene, benzo[a]anthracene, benzo[b]fluoranthene, Benzo[j]fluoranthene, Benzo[k]fluoranthene, Chrysene, Dibenzo[a,h]anthracene. are specified, and each content is required to be 0,00005% (by weight) or less　（Official Journal of the European Union, 15.12.2020, L423/15）.

 Figure 7

 PAHs for which regulation values ​​have been established as dyes for permanent makeup in the EU

There are various methods for producing carbon black, but PAHs may be contained as impurities in the above-mentioned production method that involves incomplete burning of a candle flame. Therefore, if carbon black is used in products to be exported to the EU as “permanent makeup pigments”, it is necessary to check the above PAH content.

By the way, I introduced a medical literature describing a method of making carbon black from soot. This is legal if doctors make their own for treatment, and if they try to commercialize it and sell it in the EU, they will have to measure PAHs.

In Japan, there are no regulations on permanent makeup pigments, so no matter how high the concentration of PAHs are contained in a product that uses carbon black as a raw material, it is not  illegal to sell it as a pigment for permanent makeup. But on the contrary, it is precisely because it is such an unregulated country that permanent makeup has been positioned as a medical practice, and we medical practitioners need to wisely select the pigments to be used.

Iron oxide

Iron oxide has various colors depending on its oxidation number, for example, iron(III) oxide-hydroxide (FeHO2) is yellow, iron(III) oxide (Fe2O3) is red, and so on. Since it exhibits a color tone, it is useful for producing a color.

Iron oxide is non-allergenic and non-carcinogenic. The only problem would be the MRI scan.

There are two points to note in MRI examinations. One is the problem of image artifacts (Tattooing of eyelids: magnetic resonance imaging artifacts Ophthalmic Surg. 1986 Sep;17(9):550-3, Mascara and eyelining tattoos: MRI artifacts Ann Ophthalmol. 1989 Apr;21(4) :129-31), and another is the risk of burns.

Image artifacts are diagnostic and are not clinically significant because they remain anatomically superficial. It is enough to know as knowledge.

Figure8

An MRI image of permanent makeup pigment containing iron oxide applied externally to one eyebrow and eyeline. Artifacts are missing black like the red arrows.

 The second is the risk of burns. The reason why burns can occur is due to “Faraday's Law of Electromagnetic Induction”. Eddy currents are generated when a magnet is brought close to a conductor. Electric current produces heat and damages tissue. Since some iron oxides are conductors, eddy currents may occur under the strong magnetic field of MRI.

Figure 9

 Image of Faraday's Law of Electromagnetic Induction

 Imagining from Faraday's law, it seems intuitively that ring-shaped tattoos are more likely to cause burns. If the upper and lower eyelines are connected in a ring shape, it may be safer to keep your eyes closed during the MRI examination.

Figure: 10

A copy of an image in a medical paper that first reported burns during an MRI examination. When a patient with a tattoo on his abdomen underwent an MRI, “the patient developed a sudden burning pain in the left lower quadrant of the abdomen at the site of a decorative tattoo. No scan was made, and no radiofrequency pulse was generated. The patient was removed from the suite, and the pain decreased immediately and was gone after 15 minutes. Swelling and erythema of the skin  around the tattoo site resolved in 12 hours, with no evident permanent sequela.” Multiple rings are included as tattoo shapes. After that, the tattoo site was excised at the patient's request, and  when the magnet was brought close to the skin piece, the skin piece was attracted. It is likely that many magnetic substances such as iron oxide were contained in the pigment. (MRI interaction with tattoo pigments: case report, pathophysiology, and management Plast Reconstr Surg. 1997 May;99(6):1717-20)

Most reports of MRI burns are first-degree burns, such as a burning sensation or redness that disappears in a few hours, but there are rare reports of second-degree burns (e.g., Tattoo-induced skin burn during MR imaging AJR Am J Roentgenol. 2000 Jun;174(6):1795). There have been no reports of third-degree burns. In the first place, normal burns progress from the surface of the body to the deep part by the heat source from the outside, so there are classifications from 1st degree to 3rd degree depending on the depth of damage from the epidermis → dermis → subcutaneous tissue, but in the case of heat generation due to electromagnetic induction, burns occur around the implanted pigment, so the classification itself is useless. Pigment is usually in the upper layer of the dermis, so in that sense, even redness that disappears in a few hours can be said to be a second-degree burn.

Although it deals with tattoos in general, there is a paper that collects reports of patients with tattoos undergoing MRI and having burns in the past (Tattoo complications and magnetic resonance imaging: a comprehensive review of the literature Acta Radiol. 2020 Dec;61(12):1695-1700). There were 17 cases, and the depth of the burns was described as 1st degree in 2 cases and 2nd degree in 1 case, and none of the cases left sequelae. In terms of site, there were 5 cases of eyelids, and eyelines were considered to cause many troubles during MRI examinations. However, the symptoms were mild, such as burning sensation and swelling, erythema, and tingling. The area around the eyes may be because it is a sensitive area.

In conclusion, it can be said that the risk of burns does not preclude MRI examinations even in patients with permanent makeup or tattoos. If the patient feels discomfort during the scan, it would be good to temporarily stop the scan and rescan while cooling down with ice pack.

Titanium oxide

Titanium oxide is white, and if it is added to black pigment, it becomes gray, and if it is mixed with red and yellow pigment, it becomes a color close to skin color. It is often added to pigments for permanent makeup to produce gradations and mild tones, but they have two major problems.

One is paradoxical darkening. It is a phenomenon in which permanent makeup and tattoo areas turn black when irradiated with laser light. There are many doctors who have experienced that when they tried to remove traces of old permanent makeup and spots near the eyebrows with a laser which turned black instead, aren’t they?

In fact, iron oxide also causes paradoxical darkening, but unlike iron oxide, titanium oxide is originally white, so the change is large. This makes it more problematic.

As a treatment when paradoxical darkening occurs, if it is a small area, it is better to transpire it with a carbon dioxide laser and remove it like removing a mole.

Blackening is obvious immediately after irradiation, so when laser irradiation is applied to the vicinity of permanent makeup, you should first try to irradiate one spot as a test to check it, and if it turns black, scraping off that part immediately with a carbon dioxide gas laser can avoid complicating the problem.

If black discoloration occurs over a wide area, the laser treatment can be repeated in the same manner as removing a black tattoo.

Figure 11

Example of paradoxical darkening. It is speculated that the physician tried to remove the old permanent makeup on the outer corner of the eyebrow with a laser. Reproduction of a figure in “Treatment of Cosmetic Tattoos: A Review and Case Analysis Dermatol Surg. 2018 Dec;44(12):1565-1570.”

Figure 12

A case where when a seborrheic keratoma was irradiated with an alexandrite laser, the area that had previously been covered with skin-colored cosmetic tattoo for camouflage turned black. After that, it was treated with a carbon dioxide laser (Carbon Dioxide Laser Correction of an Occult Camouflage Tattoo Unintentionally Darkened by Q-Switched Laser Exposure. Dermatol Surg. 2015 Sep;41(9):1091-3).

Figure 13

An example of blackening only the edge of a lip tattoo when irradiated with a Q-YAG laser (532 nm) for the purpose of removing a tattoo. Good results were obtained as in (c) by subsequently irradiating the laser with a wavelength of 1064 nm three times (Q-switched Nd:YAG laser for cosmetic tattoo removal Dermatol Ther. 2019 Sep;32(5):e13042.)

 Another problem with titanium oxide is its photocatalytic activity. Although it is a laboratory level, photocytotoxicity has been confirmed by adding titanium dioxide to fibroblasts and irradiating ultraviolet and visible light.　（Photocytotoxicity in human dermal fibroblasts elicited by permanent makeup inks containing titanium dioxide J Cosmet Sci. 2011 Nov-Dec;62(6):535-47).

 Photo-induced granuloma may occur in permanent makeup sites. There is a paper that considers the possibility that titanium dioxide acts as a photocatalyst and generates hydroxyl radicals from other azo dyes, etc., which may cause photo allergy (Photoinduced granulomatous reaction of cosmetically tattooed lips J Cosmet Dermatol. 2020 Dec;19(12):3423-3425).

From the viewpoint of avoiding the risk of allergic reaction, attention should be paid to pigments containing titanium oxide.

Azo dye

 Azo dye is a general term for organic compounds in which two organic groups are linked by an azo group R-N=N-R'. It does not exist in nature and is synthesized artificially.

 Although there are various dyes in the world, about 4000 of the 7000 registered dyes are said to be azo dyes. Most of the prints on our everyday clothes are made with azo dyes.

 It is often added to permanent makeup pigments because of its vivid and diverse colors, but there are some problems. These are the carcinogenicity problem, the allergy problem, and the color fading problem.

 These three problems are basically the same. This is because azo dyes are chemically changed or decomposed by an enzyme (azo reductase) or light. Have you ever been annoyed by the experience that even if the permanent makeup looks beautiful right after the treatment, it will turn green or red within a few years? This is because the azo dye contained in the dye chemically changed and faded.

 In such cases, when non-medical personnel performed the treatment, azo dyes were added based on the simple idea that, for example, if the color changed to green, the complementary color reddish purple should be touched up. However, in the era of medical permanent makeup, that alone is not enough.

 For example, acid red 114, a red azo dye, is converted to 3,3'-Dimethylbenzidine, which is carcinogenic, by reductive decomposition. About 5% of azo dyes are said to produce carcinogens by such decomposition.

Another problem is allergies. There have been many cases in which patients suspected of having an allergic reaction to tattoo pigments were patch-tested with the pigments, but the results were negative and the cause could not be identified　（Patch test study of 90 patients with tattoo reactions: negative outcome of allergy patch test to baseline batteries and culprit inks suggests allergen(s) are generated in the skin through haptenization Contact Dermatitis. 2014 Nov;71(5):255-63）.

 Even if the substance before decomposition is not carcinogenic, the substance after decomposition is carcinogenic. In the same way, even if an azo pigment before decomposition does not cause an allergy, an allergy may be established to the substance after the decomposition.

 For substances such as azo pigments that are metabolized and changed in the body, even if a patch test is performed in advance as a countermeasure against allergies and a negative result is confirmed, there is no sense of security.

 Azo dyes are commonly used as cosmetic materials, and some manufacturers claim their safety on the grounds that they are approved by the FDA in the United States. However, it is in a state where it adheres to the skin surface and is not decomposed, that is, in a usage that is assumed to be washed off in a short time. Intradermal injections and long-term indwelling can lead to nasty complications when allergies are caused by products degraded by enzymes or light.

 This is just my opinion, but I think that pigments containing titanium oxide or azo pigments are not suitable for permanent makeup. Don't forget the essence of medical permanent makeup because you are too particular about bright colors and subtle tones.