Background/Aims: Tattooing is a global trend. Clinical knowledge of complications is based on case reports collected over a century. Larger cohorts reflecting complications associated with contemporary trends are lacking. Methods: The study was a retrospective review of a consecutive cohort of patients with tattoo complications diagnosed in the “Tattoo Clinic“ of Bispebjerg University Hospital in Copenhagen, Denmark, from 2008 to 2015, based on patient history and systematic clinical examination. Results: A total of 493 tattoo complications in 405 patients were studied. Overall, 184 (37%) presented allergic reactions with plaque elevation in 32.2%, excessive hyperkeratosis in 3.7%, and ulceration in 1.4%, predominantly observed in red tattoos and nuances of red; 66 (13%) presented papulo-nodular reactions, mainly observed in black tattoos (considered non-allergic) and due to pigment agglomeration; 53 (11%) had bacterial infections; 46 (9%) were psycho-social complications; 144 (30%) belonged to several specific diagnostic entities, including photosensitivity, pain syndrome, and lymphopathy. We found no cases of cutaneous or other malignancies. Sarcoidosis was primarily seen in black tattoos and was a common associated disease, found in 23 reactions (5%), compared to the background population. Conclusion: The study introduces a new concept of classification of tattoo complications based on simple tools such as patient history and objective findings supplemented with histology. The study reflects complications originating from presently used tattoo inks, often with organic pigments. The introduced classification has been submitted to the World Health Organisation (WHO) as a proposal to the 11th revision of the International Classification of Diseases.

The allergen or allergens responsible for tattoo reactions are not present directly in tattoo ink stock products. This is despite the fact that clinical histories suggest that the vast majority of clinical reactions, especially reactions to red and red nuances, are likely to be allergic events caused by the injected inks. We suggest that the responsible allergen results from a complicated and slow process of haptenization, which may even include photochemical cleavage of red azo pigment.

Tattoos cause a broad range of clinical problems. Mild complaints, especially sensitivity to sun, are very common and seen in 1/5 of cases. Medical complications are dominated by allergy to tattoo pigment haptens or haptens generated in the skin, especially in red tattoos but also in blue and green tattoos. Symptoms are major and can be compared to cumbersome pruritic skin diseases. Tattoo allergies and local reactions show distinct clinical manifestations, with plaque-like, excessive hyperkeratotic, ulcero-necrotic, lymphopathic, neuro-sensory, and scar patterns. Reactions in black tattoos are papulo-nodular and non-allergic and associated with the agglomeration of nanoparticulate carbon black. Tattoo complications include effects on general health conditions and complications in the psycho-social sphere. Tattoo infections with bacteria, especially staphylococci, which may be resistant to multiple antibiotics, may be prominent and may progress into life-threatening sepsis. Contaminated tattoo ink is an open-window risk vector that can lead to epidemic tattoo infections across national borders due to contaminated bulk production. Hepatitis B and C and human immunodeficiency virus (HIV) transferred by tattooing remain a significant risk needing active prevention. It is noteworthy that cancer arising in tattoos, in regional lymph nodes, and in other organs due to tattoo pigments and ingredients has not been detected or noted as a significant clinical problem hitherto, despite millions of people being tattooed for decennia. Clinical observation and epidemiology disagree with register data, which indicate an increased risk of cancer due to chemical carcinogens present in some inks. Registers rely on chronic dosaging of cell lines and animals. However, tattooing in humans is essentially a single-dose exposure, which might explain the observed discrepancy.

Background Red tattoos are prone to allergic reactions. The identity of the allergen(s) is mostly unknown. Objectives Chemical analysis of human skin biopsies from chronic allergic reactions in red tattoos to identify culprit pigment(s) and metals. Material and methods One hundred four dermatome biopsies were analyzed by matrix‐assisted laser desorption/ionization tandem mass spectrometry (MALDI‐MS/MS) for identification of commonly used organic pigments. Metal concentrations were assessed by inductively coupled plasma (ICP)‐MS and x‐ray fluorescence (XRF). Fourteen patients had cross‐reactions in other red tattoos. Results In total, the identified pigments were mainly azo Pigment Red (P.R.) 22 (35%), P.R. 210 (24%), P.R. 170 (12%), P.R. 5 (0.9%), P.R. 112 (0.9%), and Pigment Orange (P.O.) 13 (11%). P.R. 122 (0.9%) and Pigment Violet (P.V.) 23 (8%) were also common. P.R. 22, P.R. 170, and P.R. 210 also dominated in patients with cross‐reactions. In 22% of the biopsies, no red pigment was detected. Element analysis indicated the presence of the sensitizers nickel and chromium. Conclusions P.R. 22, P.R. 170, and P.R. 210 were identified as the prevailing pigments behind chronic allergic reactions in red tattoos. The epitope causing the reaction might be a pigment‐degradation product. Metal contamination may derive from different sources, and its role in red tattoo allergy cannot be ascertained.

Background/Aims: Sarcoidosis is, from historical data, suggested to be more prevalent among patients with tattoo reactions. We aimed to evaluate this association in a systematic study. Methods: This is a consecutive study of patients with tattoo complications, diagnosed in the “Tattoo Clinic” at Bispebjerg University Hospital in Copenhagen, Denmark, from 2008 to 2015, based on clinical assessment and histology. From the overall group of 494 tattoo complications in 406 patients, 92 reactions in 72 patients showed a papulo-nodular pattern studied for local and systemic sarcoidosis, since sarcoidosis is expected to be nodular. Results: Of the 92 reactions with a papulo-nodular pattern, 27 (29%) reactions in 19 patients were diagnosed as cutaneous or systemic sarcoidosis, supported by histology; 65 (71%) were diagnosed as non-sarcoidosis due to histology and no clinical sarcoid manifestations. “Rush phenomenon” with concomitant reaction in many other black tattoos, triggered by a recent tattoo with a papulo-nodular reaction, was observed in 70% in the sarcoidosis group and 28% in the non-sarcoidosis group, indicating a predisposing factor which may be autoimmune and linked with sarcoidosis. Agglomerates of black pigment forming foreign bodies may in the predisposed individual trigger widespread reaction in the skin and internal organs. Conclusion: Black tattoos with papulo-nodular reactions should be seen as markers of sarcoidosis. Papulo-nodular reactions may, as triggers, induce widespread reactions in other black tattoos - a “rush phenomenon” - depending on individual predisposition. Sarcoidosis is estimated to be 500-fold increased in papulo-nodular reactions compared to the prevalence in the general population, and the association with black tattoos is strong.