Tattoo Ink Products and Pigments 2018–2019 Upfront the New EU-REACH Regulation: Danish Golden Benchmark Study of 108 Studios and 39,687 Clients Tattooed with Inks from 109,720 Ink Bottles

The safety of tattooing related to tattoo inks is from the regulatory view highly complex and undergoes rapid changes in Europe and globally. A historical change has taken place in all 27 member states of EU because of the decision to regulate particulate and widely insoluble tattoo pigments under the established EU-REACH system for chemical substances. REACH is a system primarily for specific chemical substances of convenient solubility used in industrial production to safeguard employees, now for the first time applied to a class of composite end-user products, the tattoo ink stock products, used on clients by tattooists and directly and deliberately deposited in the skin by needle injection.

Safety of tattoo ink stock products rely on the chemical purity of supplies of the pigment raw material from the bulk industry, production of ink stock product by industrial tattoo ink manufacturers, sales and distribution channels on different continents involving local suppliers and the final storage and use in studios on clients. Final step is safe handling of used inks and inks beyond expiry as chemical waste.

In the past the legal framework on tattooing and inks was very loose, inconsistent, and scattered thus with no European or global harmony. The declared aim of the recent development in tattoo ink legislation in Europe is to restrict potential mutagenic, carcinogenic, and reproduction-toxic ink ingredients; microbial contamination and sterility not addressed. The regulatory process has been reviewed by the German Federal Institute for Risk Assessment [1]. Huge knowledge gaps in science remains and the new regulation is bound to be widely based on assumption and political decision [2, 3]. The safety of inks on use in studios involves different aspects beyond the chemical composition of ink products such as the handling, storage, technique of injection, and the interaction with clients; a seamless strategy with all risk issues covered is logic [4].

The many risk elements of tattooing already were analyzed and penciled in legal, toxicological, chemical, production, business, and medical contexts [5‒10]. Prevention of disease is the supreme endpoint. Microbiological contaminants, allergens, photosensitizers, and pigments causing granuloma and sarcoidosis are important in view in the documented clinical spectrum of adverse events related to tattoos [11‒22]. The epidemiology of clinical adverse reactions has been studied by questionnaire in German speaking countries followed by a survey of the literature [23, 24]. A broad range of acute and chronic problems was reported. Long-term events may according to Danish studies be mild and chronically intermittent complaints, often irritant in nature and dominated by photosensitivity reported in 1/5 [25‒30]. Mild complaints were noted in about 40% of the tattooed population, but only 2–3% of tattooed individuals had contacted a medical clinic or a doctor. A study from New York Central Park found 10.3% self-reported adverse tattoo reactions, 6% reported as chronic [30]. Chronic reactions diagnosed in clinics are dominated by allergies especially in red tattoos followed granulomatous sarcoid reactions in black tattoos. The allergens or the haptens are not identified albeit chemical analysis of biopsies from allergic tattoos suggested Pigment Red 22, 170 and 210 as potential candidates [31]. Patch test with suspected culprit tattoo inks is negative, and metal reactions to nickel and chromate not increased relative to non-tattooed [32]. History with lag time counted in months or years between tattoo and clinically manifest tattoo allergy indicates that the allergen is a hapten formed in skin over time from breakdown chemicals, predominantly in red tattoos from azo-pigments.

However, bacterial infection in the healing phase of the new tattoo clearly remains the most frequent medical complication [14, 23, 24]. 6% and 3% of infections could be attributed to the tattoo ink or to the studio, respectively [15]. 10% of new ink bottles were shown to be contaminated with pathogenic bacteria, independent of labelled sterility [13]. Infections often are treated by general practitioners. Invasive infection with sepsis remains the main reason of death from tattooing and the foremost threat to the client. Hygiene practices are vigorously implemented in the studios supported by a recent EU CEN standard [33].

Tattoo ink products are international and move across continents and borders. More than 90% of inks used in Europe are manufactured in USA [6, 8]. Inks are industrial products made with no formal Good Manufacturing Practice (GMP) standard albeit the established industry spontaneously is moving in that direction [34]. The ink industry is facing a difficult-to-meet challenge in the move from present state to a future of very strict regulation of the chemical content of ink products, a challenge the industry cannot meet [35]. Ink production logically ought to adhere to the standards for sterile production and product documentation required for pharmaceutical injectables.

A nonbinding standard on chemical composition of tattoo inks of the European Council launched in 2003 and revised in 2008, ResAP(2008)1 introduced restrictions on chemical ingredients, impurities and contaminants in tattoo inks regarding mutagenic, carcinogenic, and reproduction-toxic elements and the content of metals [36]. This standard was officially adopted by 10 EU member states, however, in different national modifications. The implementation of ResAP(2008)1, thus, has been geographically scattered and therefore of no measurable influence on client’s safety manifested as disease. The Swiss authority adhering to the 2003 version of the Council resolution in campaigns in 2011 and 2014 with chemical analysis of inks from studios banned 37% and 50% of measured inks because of the content of potential carcinogens or unacceptable preservatives [37, 38].

EU initially attempted to regulate tattoo inks as consumer products; however, regulation of tattoo inks as chemicals under the REACH registration system ended being the decided strategy. The Joint Research Center in Ispra, Italy in four extensive reports made the preparative analytical and descriptive work, seconded by reviews by the European Society of Tattoo and Pigment Research (ESTP) and others [5‒9, 39]. Chemical control remains being hampered by lacking EU standards on analytical methods including nonavailability of a range of high purity laboratory reference substances; moreover, there is little knowledge on biokinetics, and clinical implications related to the many specific tattoo ink particles, chemicals, and impurities applied to human skin by tattooing [3, 4, 6, 8, 39, 40]. The EU chemical agency ECHA in Helsinki, Finland has identified 4,130 restricted substances in the new EU regulation [41]. The new regulation is binding to member states. The regulation introduces no prelaunch approval of tattoo ink products and no positive list. Pigment Blue 15, the only blue pigment in use, is banned with no known substitute. The new scenario marks a dramatic change for the tattoo studios and the ink manufacturing industries in Europe, USA, and Asia.

The pigment raw material bulk industry makes thousands of tons annually for the very broad range of stained items in modern society including paints and dyes. They are neither geared for nor interested in small-scale production of high purity and high-priced pigments for tattoo inks used on human skin. The specialized tattoo ink manufacturers are not equipped for elaborate raw material and production control involving advanced chemical analyses required. Neither are national competent authorities in Europe, with Germany, the Netherlands, Italy, Sweden, and Switzerland as known exceptions, equipped with a battery of validated analytical methods needed for routine surveillance of the chemical ingredients of tattoo inks in use in studios in the respective country.

EU according to Directive 2001/95/EC in 2005 established a notification system exclusively open for authorities’ input, where rapid alerts on consumer products imposing serious risk to the users are collected; the RAPEX system [42, 43]. It includes tattoo ink products along with toys, jewelry, clothes, electrical devices etc. RAPEX is not a clinical hazard-database, and the declaration of “serious risk to humans” may appear misleading. Notifications on tattoo ink risk events since 2005 are a few hundreds and include trivial events such as incorrect labelling. The French National Agency for Medicines and Health Products’ Safety (ANSM) has established a national system for surveillance of tattoo-related adverse events with registration of manifested medical events in tattooed individuals. Customers, tattooists, doctors, and institutions can submit reports on culprit inks, but the registry is not accessible to the public. In USA, the Food and Drug Administration (FDA) for many years uses a surveillance system, the MedWatch, which includes clinical tattoo adverse events reported by the public and by tattooists and medical professionals [44]. The policy is watchful waiting focused on real and significant clinical events coming out of consumer reports. The system successfully identified local outbreaks of tattoo ink infections with Mycobacterium Chelonae [45].

2019 is a year of special opportunity since confounding Covid-19 infections had not yet entered the scene and because Danish tattooists by law were forced to make detailed records on individual clients and the specific tattoo inks products applied. The new law of June 6, 2018 (law effective from January 1, 2019) required that tattooists shall register the brand, color name, distributor/manufacturer, lot/batch number, color index number, date of use and expiry. Registrations shall be kept for 5 years. The client shall after the tattoo session be given printed information about the precise ink used on his request. 2019 is positioned to be the golden benchmark and year nil reference for surveillance in the years to come of the influence of the new EU regulation on the use of tattoo inks directly in studios and directly on clients. Denmark has the potential to become an important index country in the monitoring of the impact of the new EU regulation on tattooing practice in service of the safety and health of tattoo customers.

The focus of this study is to describe large scale the tattoo inks used by tattooists and have the pigments labelled on ink bottles registered including those pigments declared to be unsafe and restricted in future inks according to the new EU regulation. This is a key requisite in future clinical and epidemiological study of tattoo complications including the potential cancer risk and the effect of the regulation hopefully making tattooing safer. Many complications appear after years. The cornerstones of the InkBase system applied are the studio, the ink bottle, and the client, Figure 1. The system operates using a central database and additionally links to the RAPEX and FDA surveillance systems. The database meets Danish regulations of registries and EU requirements on personal data protection. The data entered are those required according to the Danish tattoo law of June 6, 2018. The system is developed by InkBase and Miks Tattoo/Bjørn Severin, Copenhagen, Denmark. Tattooists pay a fee to be connected to the system with access to services. The system is maintained by InkBase/Esben Hammershøy, who is also responsible for the storage of labelled samples for research, under proper and secure conditions. Miks Tattoo is a consolidated studio, family owned for generations and respected. The stock is maintained in cooperation with Bispebjerg University Hospital, the Tattoo Clinic.

All studios have their own secluded database where the data are stored. All users of the system have their own personal login ID and password. No unauthorized access is possible. Newly acquired tattoo ink bottles are registered in the local database in the studio under a unique barcode. Product specifications according to product label are registered with name of manufacturer and distributor, product name, lot/batch no., labeled expiration date and the pigment identified by color index (CI) number(s). The same barcode is used to code information on client identity, date of session(s), anatomical site of the tattoo, etc., into the person’s file. At end of the tattoo session, detailed ink information are printed and given to the client on request as a “passport.” The client log is accessible when the client on some future occasion may requests a new tattoo made with the same ink. Authorities and medical providers can on client’s permission be granted access to the registry. No industry-servicing tattooists including manufacturers and distributers of tattoo ink stock products can obtain access to the database.

In case a client encounters an allergic reaction to a tattoo ink or suffers some other health problem exemplified by bacterial infection during the healing phase or a chronic allergic reaction, the client and the tattooist can retrieve information on the precise ink product used and convey it to the doctor treating the condition. InkBase data can if a specific ink or a specific pigment is the reason for systematic complications upon client’s permission inform other tattooists and the local authority about the problem. The client can, when a studio closes business, contact InkBase customer service. Session and client information are stored for a minimum of 5 years according to law.

InkBase on an every-day basis will survey the use of inks. Alerts raised by the national competent authority or other organs are at any time researched in the database, with information of the studio using problem ink(s). If ink products are formally removed from the market InkBase will with no delay disseminate such message to the studios and assure inks of concerns are not used on clients. EU RAPEX notifications and FDA warnings on tattoo inks are automatically communicated to studios, who can trace clients exposed to such inks. Thus, the system is besides the function as a database also a platform for communication in the interest of safety and protection of tattoo clients.

InkBase will report to the exposed customers, the tattooists, and the national authority if significant clinical problems related to individual tattoo inks are brought to attention. Authorities have no direct access to the InkBase database, and the data are not accessible for public control or policing of individual studios and tattooists. InkBase data are not used for direct or indirect promotion of any commercial products.

InkBase has organized a library of product information sheets provided by manufacturers, and photos of bottles with close-up photos of labels. InkBase has established a physical stock of original ink product samples, which are granted for research on the request of researchers, institutions, and authorities for chemical analysis and assessment of ink-related hazards.

The registration by InkBase has been in operation since March 2018. Data from 108 tattoo studios in different parts of Denmark are presented in Table 1. There are in total about 350 registered studios in Denmark.

Table 2 shows the distribution of pigments in 22,301 ink bottles. Bottles often contain a blend of pigments. Color code by CI number was readable in only 10,833 bottles; suggested allergenic pigments are highlighted [31].

Registered ink manufacturers and ink suppliers/distributors are shown in Tables 3 and 4. The top-50 used tattoo ink brands by number of bottles are shown in online supplementary Table S1 (for all online suppl. material, see https://doi.org/10.1159/000543455). Very many inks are in use. The total number of bottles used was 14,452. Number of bottles is not a direct measure of amount or volume of ink. Black and white inks are mainly sold as 200 mL bottles, red inks, and the more popular main colors as 30 (or 60) mL bottles, and the uncommon colors and special nuances as 15 mL bottles.

The top-50 used tattoo ink products by number of tattoo sessions are shown in online supplementary Table S2. The total number of sessions was 50,604 performed in 39,687 clients.

InkBase among the 108 users of the registration system rated the studios with respect to studios’ estimated compliance with the system. Result is shown in online supplementary Table S3. The assessment of 20 high-performers and 20 low-performers was based on continuity of reporting and number of reports realistically matching the size of the studio and the number of tattooists working in the studies. The data illustrate compliance with the registration system. The data indicated that the activity of studios varied, but the numbers of ink bottles used per client in the three groups, nevertheless, were close. However, the group of low-compliance studios showed a trend to preference of less common inks. The assessment indicated that some studios from time to time missed to register specific clients and the inks used. Poorer compliance also may reflect small enterprise and irregular activity.

EU RAPEX notifications related to specific products and manufacturers, and clients exposed to the products, are shown in Table 5. 126 clients were tattooed with 32 tattoo ink bottles in “bad standing,” identified by product name and batch number, used by different studios. All RAPEX notifications at that time were on content of potential carcinogens above the defined threshold. US FDA during the study period only released one formal warning at the federal level, on an ink contaminated with bacteria; the strain was not mycobacterial. The Danish competent authority in 2011 banned 13 inks identified by brand name, producer, lot/batch number due to high content of potential carcinogens namely aniline and O-anisidine3,3-dichlorbenzidine. 9 banned inks with other batch numbers had come into use again, registered in the InkBase system (Intenze INK: Cherry Bomb, Light Green, Lemon Yellow; Bright Red; Eternal INK: Crimson Red, Dark Red; StarBrite INK: Tribal Black, Crimson Red, Grape Ape). 4 banned inks were gone (StarBrite INK: Rusty Orange; Mom’s Ink: Agent Orange; TATTOO, a low priced poorly labelled ink from Asia: Tattoo Brown, Tattoo Red). Authority had made no follow up of their banding. Ban was associated with batch number; future batches were technically legal. The Danish Authority in 2012 published the results of chemical screening of a broad range of inks on the Danish market, in total 61 inks [46].

The EU regulation bans some pigments and limits others to pigment concentration not exceeding 0.1% in a final stock product, which is much too low for an ink to be colorful in situ in skin. To be suitable inks typically hold pigment in the range 15–30%. The InkBase reported pigments included Pigment Blue 15 (CI 74160) and Pigment Green 36 (CI 74265). Blue has no known substitute ready for tattoo inks, and Pigment Green 36 was the leading green pigment. The Pigment Green labelled CI 17757 (orange pigment) is an obscure blend with orange originating from printing and publishing. The tattoo industry suffers a major problem with suitable inks for blue and green tattoos. Among 13 red inks 4 are bound to the 0.1% limit namely CI 12477, 12315, 12466, and 12390. Among 6 yellow pigments one is limited, CI 11767, and among 4 orange pigments 2, CI 21160 and 21,110. Our record of “old” inks clearly indicates a coming major shift in tattoo ink stock product composition as a necessity in legal practice. The mandatory change of inks is a historical change and a culture shock in the entire industry. The landscape of active manufacturers and suppliers will undergo dramatic change depending on their territory.

In Denmark, the use of inks in studios is controlled by a ministerial chemical agency through regular visits in registered studios. Warnings may be given, and the tattooist and the studio may ultimately be penalized or closed. Other European countries have other control systems. Policing never can be perfect and fraud can be a challenge. A close look on InkBase data already indicates a few studios are presently underreporting despite legal obligation to register inks used om costumer, which does not automatically say or prove illegal inks are used. “Old” inks sold in the rest of the world may still be used and maybe not registered in the InkBase record by the tattooist. However, the tattoo industry has in many ways, driven by the tattooist themselves and exemplified by significant progress in hygienic tattooing, made a significant move in the direction of safe and legal business. It is likely that the new EU regulation will mark a major shift and influence practices; paralleled by improved tattoo safety or not; future to show.

The aim of the new EU regulation of tattoo ink products according to their chemical composition is to improve the safety of tattoo clients. Allergic reactions in red tattoos are among the group chronic tattoo complications the largest segment in the clinic; the tattoo pigment or a chemical breakdown product of the pigment is considered responsible for the problem [10, 11, 17]. Analysis of skin biopsies from human skin with allergic reaction indicated that the red azo-pigments CI 12475, CI 12477, and CI 12315 are the primary suspects behind the allergy problem [31]. However, the allergen and the epitope remain not identified, and haptenization in the skin over longer time originating from chemical breakdowns of the pigment is suggested; thus, the allergen is unlikely to be direct present in ink stock product bottle. Inks with the three mentioned pigments are in use and may according to a policy of minimum potential risk to clients be omitted [47]. Using the InkBase system inks made with suspected harmful pigments can be identified as well as the clients, who were already exposed. Any tattoo reaction or associated problem being diagnosed, not limited to allergy, can via the client and the system be traced to the precise ink stock product and pigment used. Granulomatous reactions with or without systemic sarcoidosis in a black tattoo may be caused by some ink brand with carbon black pigment having special physical property prone to biological interaction with granuloma formation [11, 12, 18]. In both examples, specific ink products and manufacturers can be identified and notified about a product of special concern. Chemical contents of inks classified potentially carcinogenic, mutagenic, and reproduction-toxic in toxicology is presently a hypothetical problem in the context of tattoos since there has been established no proof of a manifested malignant clinical correlate documenting clinical or epidemiological relevance of such safety concerns in the tattooed population. Carcinogenicity of chemicals is generally accepted as being context and exposure dependent. Recent regulations of tattoo inks by EU and other nations are primarily driven by fear argued from standard preclinical toxicology risk assessment models, which are not validated with respect to insoluble tattoo pigments installed single dose and having vary special biokinetic profile that is poorly researched. Pigments are microparticles of extremely low solubility and very different from soluble substance. This feature makes pigments stay permanently in skin.

The InkBase system registered over a 22 months period in total 39,687 clients tattooed in 50,604 sessions. The clients were tattooed with ink from 109,720 bottles of different colors. Registration involved 108 studios. There is in Denmark about 320 registered professional studios employing about 700 active tattooists; amateurs and backyarders not considered. Thus, the system operated large scale and covered a large segment. The sample size allows detection of deviant or exceptional inks of special concern. Reports to the system came from different regions of Denmark and were proportional to the size of the population in each region (data not shown). Data were considered representative for Denmark and professional tattooists. The distribution of inks used was deemed independent of compliance with the registration system. Collected data are seen as robust and representative.

Tattoo ink products used in Denmark were clearly dominated by brands manufactured in US, e.g., 98.1% of all inks; 57% were purchased from primarily European distributors located outside Denmark. Tattoo ink supplies on the European continent are already known to be dominated by US-products as shown in an EU Joint Research Center report (6). Large ink manufacturers are operating worldwide. Their products hitherto met little regulation and few import restrictions in the different countries. The already weak position of Europe’s national tattoo ink industry with few small enterprises is now face to face with strict EU regulation under the REACH system introducing heavy baseline costs for chemical control of ink production with batch to batch quality control. Imported ink products noncompliant with EU requirements may remain being used under cover, dictated by customer demands and the need of the tattoo studios to stay in business and continue to work with the tattooist’s preferred inks, whether REACH compatible or not. It is a serious issue that the pigment blue 15 having no realistic alternative and despite favorable toxicology documented in an extensive report is banned [48, 49]. There is a risk that part of the tattoo industry will be criminalized and beyond control. Coming new regulations from UK, Australia, and USA are announced to accept Pigment blue 15 in tattoo inks.

Europe hitherto in the control of tattoo inks and chemical ingredients was guided by the Council of Europe resolution ResAP(2008)1 [36]. However, this guidance was nonbinding and failed to be implemented efficiently. RAPEX notifications on tattoo inks are few and often irrelevant for clients’ health risks. Policing the tattoo industry efficiently obviously requires huge resource and competence; bound to be scattered and imperfect. Denmark in 2011 banned 13 inks with reference to the resolution, with no follow-up or further actions. Switzerland, Germany, Italy, Spain, France, and the Netherlands have been more active, and these countries are equipped to analyze tattoo pigments, impurities, and contaminants for research purposes but not for systematic routine control of studios [37, 38]. Policing through systematical chemical analysis of inks obtained from studios is not practicable. Old tradition for alternative paths prevails in the tattoo industry having a rebellion past.

Toxicologist’s primary concern is on mutagenic, carcinogenic, and reproduction-toxic events related to primary aromatic amines and polycyclic aromatic hydrocarbons, which may be found in inks as breakdown chemicals, impurities, or contaminants. Metals and metal sensitizers along with preservatives also are of concern. However, skin cancers including melanoma occurring in tattoos are in a published Lancet review concluded few and likely to be coincidental thus unrelated to tattoo pigment [19]. There appears in the entire medical literature no single case of convincingly proven external or internal cancer directly caused by a tattoo. Keratoacanthoma is the only tumor related to tattoos, and this tumor is clinically benign despite the unsolved puzzle of malignant signs in histopathology [50, 51]. Heavily tattooed persons including nearly full skin tattooed persons with magnum exposure to pigments have not been reported dead, invalidated or especially diseased from tattoo pigment. Kluger studied 448 French tattooists, who reported no special occurrence of cancer, and female tattooist could not report any increased rate of stillbirths and fetotoxic events [52, 53].

Relationship between tattoo and cancer found no support in studies of mice tattooed black or red on their back with two inks banned from the Danish market due to contents of potentially strong carcinogens [54, 55]. The tattooed back was exposed to carcinogenic UV light throughout 1 year to provoke photochemical breakdown of pigment and skin cancer. Tattoos not exposed to light and untreated mice with no tattoos served as controls. Carcinomas in black tattoos given light unexpectedly were delayed. However, in red tattoos cancers (including keratoacanthomas) were slightly but statistically promoted. Black and red tattoos not exposed to light but exposed to the two banned inks developed no cancers in comparison with non-tattooed skin. Autopsy and histology of internal organs including the liver, kidney, spleen, bladder, and regional lymph nodes showed no cancer in any group of mice [56].

Distribution of pigment from skin to regional lymph nodes is known to be obligatory. The nodes thus are the primary cancer risk organ. It was shown in mice that pigment particles in minute amount may reach the liver via the blood, held in the Kupffer cells as part of the physiologic clearing of circulating microparticles [57]. Tattoo causing cancer has found no support in neither animal research nor in the clinic. The concern remains hypothetical.

Tattooing is single injection only, and very little is known about the immediate and long-term biokinetics and release of chemicals from tattoo pigments [39]. Pigments are micro- and nanoparticles of low solubility and the degradation in vivo of the range of different pigments is poorly understood [40, 58]. Tattoos somehow fade over time, and it is likely that there is a two-phase kinetics with early distribution of pigment out of the tattoo followed by local breakdown of pigment wherever it is positioned and slow elimination over years. Biokinetic profiles were extensively studied by the Regensburg group, focused on synthetic high purity Pigment Red 22, an azo chemical [59‒63]. Studies indeed confirmed that local breakdown to widely unknown cleavage products take place, and significant amounts of the pigment are distributed out of skin with potential exposure of other organs, primarily deposition in lymph nodes. Final stage is elimination by the liver or the kidneys [64]. However, results of a few azo-chemical pigments cannot be extrapolated uncritically to other pigments such as carbon black, phthalocyanines, chinacridones, and the iron and titanium dioxides.

The purity of industrial pigments used in inks is low and potentially harmful impurities and contaminants often are found in the raw material used in ink production. Breakdown after pigments are injected in the skin also may lead to formation of harmful substances particularly epitopes and haptens, which after months or years may cause chronic tattoo allergy in red but seemingly never in black tattoos. Carbon black has special physical properties, associated with sarcoid granuloma formation and induction of reactive oxygen species, ROS [11, 65‒68]. Autoimmunity appears associated with carbon black functioning as an adjuvant. A recent black tattoo can trigger a “rush reaction” in various older black tattoos, outbreak of iritis, joint reaction, erythema nodosum, and even fully developed sarcoidosis with lung affection. “Rush reaction” is not exceptional [11, 12, 17, 21]. Inks stock products and carbon black raw materials causing sarcoidosis should be identified and eliminated from the market. The black pigment and sarcoidosis clinical issue is not addressed and not safeguarded in the EU-REACH regulation.

Development of safe tattoo ink products might build on state of art toxicological methods used in the development of pharmaceuticals. An expert group under the Council of Europe concluded that a reliable a valid test algorithm for formal approval of tattoo ink products using standard methods is not applicable primarily since tattoo pigments are robust and widely insoluble nano- and microparticles [68]. The pragmatic approach with ink and pigment registration in the routine of studios combined with and linked to surveillance of clinical adverse events is a realistic and a logic safety approach. Surveillance of inks also can be performed using modern media, and clinical information on adverse reactions added. A French study with data invited through the French organization of tattooists SNAT and over Face Book in October 2020 with reports from 598 tattooists provided a detailed list of ink products in use in France at that time, thus, before the REACH regulation [69]. In total 66 different brands were used, 18 by more than 5% of respondents. Observations overlapped with findings in our study. Thus, popular inks may be leads across national borders of course with some deviations depending on local supplies and preferences.

Inferiority of the EU legal framework on safeguarding tattooing in member states unfortunately is a fact and a challenge that cannot find a soon and better solution [4, 29]. There is a need for one simple tattoo ink safety protocol, which shall also include microbiological safety, labelling of ink products, and adverse event reports from the clinic as part of standard surveillance routines that can be practiced throughout EU. Labelling of inks often is misleading [70, 71]. The German Federal Institute for Risk Assessment (BfR) has analyzed the regulatory challenge and in a publication provided the contour of a 3rd generation regulation of tattoo inks with a positive list included [1]. The European Society of Tattoo and Pigment Research (ESTP) has in public hearings of the REACH regulation emphasized the need for a separate EU regulation specifically on inks. REACH is established especially for soluble industrial chemicals and not suited for very composite and insoluble physical particles in the nano- and micrometer range. Microbial contaminants of inks and sterility not covered furthermore exemplify the inappropriate regulation of inks under REACH. A recent extensive review on patch testing and tattoo allergy identified no lead allergens behind tattoo allergy, and the EU-REACH regulation is blind to the precise allergen behind red tattoo allergy, which should be avoided in inks [72]. Granuloma and sarcoidosis from black tattoos also are out of scope of the REACH regulation, thus, not prevented. Finally, cancers and mutagenic events associated to tattoos and the primary target of the REACH regulation remains not been confirmed in clinical and epidemiological studies. The REACH regulation of inks, finally, faces problems in being followed by ink producers and the tattooists, and Authorities’ policing of the situation appears not possible in practice. The challenges of the REACH regulation of tattoo inks were summarized in an editorial in the journal Dermatology of Karger AG [73].

Electronic surveillance of tattooists’ use of inks on customers is an important simple and practicable instrument in the control of the safety of tattooing as well as in the traceability of hazards and adverse reactions manifested as disease in individual cases. Our introductory study documents that electronic registration in tattoo studios is possible large scale and as a daily routine; the legal prerequisite in Denmark was tattooists’ obligation to register use of inks according to law. The electronic InkBase system cannot include registration of health information but information on the precise tattoo ink applied to a person is on customer’s consent available to hospitals and medical professionals treating some immediate or late tattoo complication. Data are in anonymized form available to researchers and authorities and thus accessible as a surveillance instrument in the spirit of ideal aims. The system is a simple tattooist-operated practical tool that can operate and fulfill its mission also in other countries. The system is not in conflict with EU-REACH but supplementary and supportive to any regional, national, and local initiatives taken to improve the safety of tattooing. The data presented in this study can serve as a gold benchmark on tattoo inks used in practice before the EU-REACH was launched, and position Denmark as an index country in future follow up.

Tattoo customers are many and counted in millions. Injection of tattoo ink in the skin is considered the commonest exposure of the general population to chemicals applied across the skin barrier and thus a major safety concern. Ink chemicals undergo slow breakdown in the skin and complications are often manifested several years after the tattoo was made. Big data obtained regularly by central electronic registration is an important method for surveillance of the use of tattoo inks at any time. A new EU regulation of tattoo inks in force from January 2022 has introduced strict regulation of potential carcinogens and mutagens in inks, however, the regulation has faced difficulty in being implemented. The data in this article are a benchmark and reference of tattoo inks used in studios before the EU regulation was launched.

The study is on use of commercial tattoo ink stock products, and the study involves no individual human data. Data including raw data are anonymous. The study requires according to Danish law no ethical approval and no consent from tattoo customers. Tattoo studios are according to Danish law not allowed to register the unique identity of tattoo customers.

Bjørn Severin and Esben Hammershøy are inventors of the InkBase registration system implemented in Denmark. This article is prepared in the spirit of ideal aims and independence of economic interest. It is not prepared as and to be used as a promotional tool relative to studios which might consider acquire the system. The article is provided as a service and as an instrument to regulators and scientists, who study or follow tattoo epidemiology, toxicology, and medical complications. The data are highly relevant to EU.

The study has no budget and has received no funding or sponsoring directly or indirectly. Data are provided free of charge. Jørgen Serup has received donations from the Bloomberg Foundation, USA and the KID Foundation, Denmark for other studies independent of the present publication.

Study conception and design: Jørgen Serup, Bjørn Severin, and Esben Hammershøy. Source data: Bjørn Severin. Data management: Esben Hammershøy and Jørgen Serup. Drafting of manuscript: Jørgen Serup and Esben Hammershøy. All authors have approved the final version.

The data sets generated and/or analyzed during the current study are not publicly available. All data on tattoo ink stock products are included. Tattoo costumer information is private. InkBase has contractual obligation not to publish the identity of studios and tattooists. Further inquiries can be directed to the corresponding author.