For the first time, science has confirmed that nanoparticles from your tattoos will end up in your lymph nodes.
Humans have been permanently decorating our skin with ink for at least 5,000 years, but we still don't really know what effect, if any, they have on our bodies.
Now, for the first time, scientists have found evidence that both pigments and impurities from the tattoo ink can travel around your body as nanoparticles.
How tattoos work is actually pretty brilliant. The ink is precisely deposited via a needle below both the dermis and epidermis, where, too big for your immune system to break down, the ink particles will remain permanently.
Laser removal breaks these particles down into small enough pieces so your body can dispose of them.
But, while most of the ink stays put, a minute amount of it does end up getting removed by the immune system. And, according to researchers at the European Synchrotron, that could be a problem, since we don't know what it could do to our body.
"When someone wants to get a tattoo, they are often very careful in choosing a parlour where they use sterile needles that haven't been used previously," said researcher Hiram Castillo.
"No one checks the chemical composition of the colours, but our study shows that maybe they should."
The composition of tattoo pigments could have an unknown effect on the body. They could, for instance, contain impurities. They contain preservatives and contaminants such as cobalt, chromium, manganese and nickel. Allergic and other reactions to tattoo inks are not uncommon.
One very common ingredient is titanium dioxide, used for white ink. This is also used to lighten other coloured pigments. The researchers tracked several of these types of tattoo nanoparticles through the body using X-ray microscopy and X-ray nanoprobe beamlines.
"We already knew that pigments from tattoos would travel to the lymph nodes because of visual evidence: the lymph nodes become tinted with the colour of the tattoo. It is the response of the body to clean the site of entrance of the tattoo," said one of the research team, Bernhard Hesse.
"What we didn't know is that they do it in a nano form, which implies that they may not have the same behaviour as the particles at a micro level. And that is the problem: we don't know how nanoparticles react."
The team tracked micro- and nanoparticles in the skin and lymph nodes. They found microparticles in the skin, but only nanoparticles made it into the lymph nodes, both of organic pigments and titanium dioxide.
They also used infrared spectroscopy to determine that there were structural changes in the tissue surrounding these particles.
Tattoos aren't all bad, though. Previous research showed that getting multiple tattoos strengthens your immune system by working it harder, like taking it to an immune system gym.
But the research could help determine not just the effects of tattoos, but substances such as cosmetics and sunscreens, which also contain titanium dioxide.
"In future experiments we will also look into the pigment and heavy metal burden of other, more distant internal organs and tissues in order to track any possible biodistribution of tattoo ink ingredients throughout the body," the researchers wrote in their paper.
"The outcome of these investigations not only will be helpful in the assessment of the health risks associated with tattooing but also in the judgment of other exposures such as ... the entrance of titanium dioxide nanoparticles present in cosmetics at the site of damaged skin."
The research has been published in the journal Scientific Reports.