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It is estimated that 120 million people worldwide have tattoos of which 12% of Europeans have at least one tattoo and 29% in the United States of the general American population are tattooed. In Germany, around 20% and more and more related adverse reactions are reported.

Tattoo inks can cause a variety of health problems, many of them particularly related to the skin, but some are also relevant to other organs (Figure 1 of the first link). Adverse effects include delayed wound healing, infections, toxic or even mutagenic processes, as well as granulomatous and allergic reactions.

Tattoo inks contain numerous substances, such as coloring pigments, impurities, solvents, emulsifiers and preservatives. Inorganic tattoo pigments are natural mineral compounds such as metal oxides (hematite Fe 2 O 3 ), salts and minerals (cinnabar HgS). Synthetic organic pigments, such as azo (mainly yellow, orange, red, magenta and purple), are synthetic compounds that give brighter and more diverse colors.

The possible dangerous properties of chemicals in tattoo inks include carcinogenic, immunotoxic and sensitizing properties. Tattoo inks containing dangerous chemicals are frequently found on the European market. The main substances of concern detected in the samples analyzed are polycyclic aromatic hydrocarbons (PAHs) (43%), primary aromatic amines (14%), heavy metals (9%) and preservatives (6%).

The pigment particles remain in the dermis and absorb light in a specific spectral range causing the color of the tattoo. Another fraction of the injected tattoo ink is passively removed from the skin via lymphatic or blood vessels or actively transported by migrating cells. As a result, the tattoo pigments are found in the local lymph nodes, but are probably also transported to other organs such as the liver, lungs or kidneys.

Experiments with mice suggest that Kupffer cells within the liver pick up pigment particles from tattoo suspensions, as indicated by particle detection by electron microscopy.

Most black pigments are typically produced by imperfect combustion of hydrocarbons that produces soot, a mixture of black inorganic carbon particles containing polycyclic aromatic hydrocarbon (PAH) molecules. PAHs are metabolically activated by their respective diol epoxides, which can bind to DNA and cause mutagenicity, resulting not only in carcinogenicity but also in effects on lymphocyte activation and macrophage differentiation.

Tattoos produce numerous holes in the skin that facilitate the entry of microbial pathogens. If pathogens enter blood vessels, systemic infections can occur. Allergic reactions to tattoos are mainly mediated by T cells, classified as type IV delayed hypersensitivity reactions.

Reactions to tattoos are reported in up to 67% of people who get tattoos, with papulonodular and granulomatous reactions being the most common. Some neoplastic complications have been described, but their causality is still debated. Any pigment can cause adverse reactions, although red ink is most frequently associated with them. Patients with pre-existing dermatoses may experience exacerbations or complications of their diseases.

Tattoos can develop inflammatory skin reactions such as sarcoidosis, pyoderma gangrenosum, atopic dermatitis and neoplasms.

https://onlinelibrary.wiley.com/doi/full/10.1111/ddg.14436 (2021).--

https://chemistry-europe.onlinelibrary.wiley.com/doi/full/10.1002/slct.202300986 (2023).--

https://medtech.mphu.edu.ua/article/view/295883 (2023).--

https://www.sciencedirect.com/science/article/pii/S2772416623001614 (2024).---

https://www.sciencedirect.com/science/article/pii/S0365059624000345 (2024)

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