If you take a look at the lymph nodes of a heavily tattooed person, you’ll notice something very strange: a microscopic sprinkling of metal.
It’s been known for some time that tattooing can result in metal nanoparticles being introduced to the body, where they're pumped around until they are caught by the immune system in a lymph node, found throughout the body, including in the armpit, groin, and neck. It was previously assumed that the contamination came from the inks, however, a new study has shown that’s not the case.
Scientists have discovered that traces of nickel and chromium found in the lymph nodes of tattooed people actually originate in the needle of the tattoo machine, as reported in the Particle and Fibre Toxicology Journal.
“There is more to tattoos than meets the eye. It is not only about the cleanliness of the parlour, the sterilization of the equipment or even about the pigments. Now we find that the needle wear also has an impact in your body”, explained Hiram Castillo, one of the authors of the study.
The team, led by researchers at the Federal Institute for Risk Assessment in Germany, started their investigation by studying the tissues of deceased tattooed and non-tattooed people. Within the lymph node tissues of the inked-up cohort, they found particles of iron, chromium, and nickel ranging from 50 nanometers to 2 micrometers in size. That might sound insignificant, but nanoparticles are potentially more dangerous than larger particles as they have a higher surface-to-volume ratio, which leads to a higher release of toxic elements.
To their surprise, these metals weren’t that commonly found in the tattoo inks, so they began to look elsewhere for the source.
“We tested around 50 ink samples without finding such metal particles and made sure that we hadn't contaminated the samples during sample preparation. Then we thought of testing the needle and that was our 'eureka' moment,” added Ines Schreiver, corresponding author and scientist at the Federal Institute for Risk Assessment.
A deeper analysis showed that green, blue, and red tattoo inks contain a white pigment called titanium dioxide, which can wear away at the needle. Black ink, however, doesn’t contain this pigment and the needle wears down less.
This discovery could help to explain why tattoos can occasionally cause allergic reactions in some people. As for the wider health implications of having a lymph node loaded with nanoparticles, that remains unclear for now. Currently, there's little to no evidence to suggest that tattoos are associated with any wider health problems, however, the researchers hope to investigate this avenue a little further before settling on any conclusion.
“Unfortunately, today, we can't determine the exact impact on human health and possible allergy development deriving from the tattoo needle wear," explained Schreiver. "These are long-term effects which can only be assessed in long-term epidemiological studies that monitor the health of thousands of people over decades."