Even clean needles may cause problems for people with tattoos, new research suggests.
It shows that particles that wear from the needle during the tattooing process could be responsible for some of the allergies usually blamed on the inks or poor sterilisation.
Tattoo needles usually contain nickel (6-8%) and chromium (15-20%), both of which prompt a high rate of sensitisation in the general population, the authors report in an article in the journal Particle and Fibre Toxicology.
Led by the Federal Institute for Risk Assessment in Germany, this project was a major undertaking, involving scientists from Germany and France and making use of the European Synchrotron (ESRF), one of the world’s most intense X-ray sources.
In earlier work, the team had discovered that inks and their metal impurities are transported to the lymph nodes – an important part of the body’s immune system – in a nanoform, where they can be found years after the placement of the tattoos.
However, they couldn’t explain the presence in the lymph nodes of iron, chromium and nickel, which weren’t part of around 50 ink samples they tested
“Then we thought of testing the needle and that was our ‘eureka’ moment,” says corresponding author Ines Schreiver.
Those tests showed that when the ink contains titanium dioxide (a white pigment often mixed in bright colours such as green, blue and red), it wears away the needle. Titanium oxide is very abrasive due to its high density and hardness compared to carbon black.
The researchers studied a needle before and after the tattoo process using scanning electron microscopy, which showed the abrasion. “It is beyond doubt that the metal particles derive from the tattoo needle as result of pure mechanical grinding”, says co-author Bernhard Hesse.
Nanoparticles – which can measure just a few nanometres (billionths of a metre) – are particularly dangerous, the researchers note, because their increased surface-to-volume ratio leads to a potentially higher release of toxic elements. They also can directly enter cells and are more easily distributed in the body, though they are more readily excreted from the body than larger particles.
Schreiver says more work is needed to clearly assess the impact on tattoo allergy formation and systemic sensitisation.