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Tattoos have never been more fashionable, driven by peer pressure and the celebrity copycat culture. Many young people have indulged in this form of permanent body art but age is no barrier, as an observant walk around your local town will reveal.
A recent survey in Germany estimated that about 10% of the population are tattooed and the figure is greater in the USA. Various polls suggest that between 12-15% of the American population has at least one tattoo, with the figure rising to 20-40% for those aged 18-50.
While there are requirements for tattoo parlours and the more upmarket tattoo studios to be registered in some countries, there is little legislation regarding the inks, which are probably responsible for the health problems experienced by so many customers. If the tattoo parlours and equipment are clean and sterilised, where else do the persistent skin irritations, allergies and lesions originate from?
A team of scientists in Germany has targeted black inks, which are the most common ink used. Wolfgang Baumler and colleagues from the University of Regensburg considered that the inks must contain impurities which react with the body when the inks are injected into the skin. There are no legal requirements to list the ingredients, so no-one knows what might be present.
In an earlier study published in 2010, they discovered that black inks contain as many as 20 different polyaromatic hydrocarbons, hardly surprising given that the inks are composed mainly of carbon black produced by imperfect combustion.
Now, they have turned their attention to the search for other compounds in black inks which could be acting as allergens or irritants.
A total of 14 commercial inks were purchased from Europe, Asia and the USA, with such exotic names as Tribal Black, Diabolo Genesis, Black Magic and Calcutta Black. They were each subjected to solvent extraction and the extracts were spiked with hexamethylbenzene as an internal standard for GC/MS analysis.
Inking in the details
The individual components were separated on a 5% phenyl methylpolysiloxane column and identified by comparison of their mass spectra with those in a commercial library. Quantification was accomplished from the peak areas of the compounds related to that of the internal standard.
A number of impurities were found in the black inks, clearly separated in the chromatograms and identified unambiguously from their retention times and mass spectra. Six of these were identified as potential irritants and their quantities were estimated in each of the inks.
A total of 14 other compounds were also detected but they could not be identified confidently, so they were not quantified.
Dibutyl phthalate was found in all 14 inks, in amounts ranging from 0.12-691 µg/g. This compound is a known teratogen, genotoxin and contact allergen, so injection into the skin would not be a recommended course of action.
Irritants and allergens in black tattoo ink
Benzophenone was found in 11 inks up to 557 µg/kg. It has been classified as an irritant and has been reported to induce photosensitisation in the skin of guinea pigs during UV irradiation. It is used in perfumery and other benzophenones are added to sunscreens but previous studies have shown that they are poorly absorbed into the blood. However, direct injection during tattooing will probably introduce larger amounts into the system, with the potential to cause irritation.
The third most detected compound in the tattoo inks was 9-fluorenone, found in 10 samples but less abundant at a maximum content of 3.04 µg/g. Little is known about its actions in vivo, although it has been reported to be a photosensitiser.
Of the remaining three compounds, hexachloro-1,3-butadiene is genotoxic and a possible human carcinogen and dibenzofuran is a known skin, eye, nose and throat irritant. Hexamethylenetetramine, also known as methenamine, is known to cause respiratory allergies.
The main problem with tattoo inks is that they are not regulated. Many of the inks examined by Baumler and Co contained at least one compound that might be responsible for adverse skin reactions after use.
"We urgently recommend regulation of tattoo inks, so that only those inks without hazardous substances may be used," says Baumler. As a first step, it should be illegal to allow the skin to be punctured by inks containing substances that are banned from cosmetics.
The researchers recognise that this list of undeclared additives in black tattoo ink is probably incomplete but say that it provides a starting point for physicians looking for triggers of adverse skin reactions to the inks.
- Contact Dermatitis 2011, 65, 231-238: "Black tattoo inks are a source of problematic substances such as dibutyl phthalate"