For better or worse tattoos are meant to stay with you forever. New research, though, suggests that their permanence is more than skin deep. According to a new study, pigments and toxic chemical impurities found in tattoo ink may travel through the body and eventually accumulate in the lymph nodes, bean-shaped structures that filter out substances as part of the body's immune system. That buildup could lead to chronically inflamed lymph nodes, though because the particles involved are so small, researchers aren't yet certain of the effects. If you have more than a few tattoos, this might sound pretty scary.
In fact, scientists know surprisingly little about how tattoo ink affects the body. Most inks contain organic pigments, but they can also use contaminants and preservatives like nickel, chromium, manganese, or cobalt. (Having those elements all up in your dermis, you can imagine, might have some kind of effect.) Carbon black is the most common ingredient in tattoo ink followed by titanium dioxide (TiO2), a white pigment that's often found in food additives and paints and is also used in sunscreen.
In tattoos, TiO2 can be mixed with colorants to create certain shades. When used to create white, it's often associated with itching, raised skin in the tattoo area, and delayed healing. Researchers wanted to trace titanium dioxide's movement through the body, focusing on the very smallest particles, and the nano and micro levels. (To give you a very abstract sense of how small we're talking, a nanometer is one-billionth of a meter; a sheet of paper is about 100,000 nanometers thick.)
"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," Bernhard Hesse, one of the study authors, said in a statement. "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."
Researchers looked at tattooed skin and nearby lymph nodes from four donor corpses and compared them to two non-tattooed control donors. Using X-ray fluorescence measurements, they discovered higher levels of TiO2 in the skin and lymph nodes of the tattooed people compared to the non-inked people. Particles as large as several micrometers appeared in the skin, but only the smaller nanoparticles migrated to the lymph nodes. It's the first study to show evidence of specific pigments and impurities traveling from the dermal layer of the skin to the lymph nodes.
Some news reports have already linked the findings to cancer, implying that tattoos may cause the disease, but that's a very premature response for such a small study. Right now scientists have shown strong evidence that toxic elements and tattoo pigments move through the body and can accumulate in the lymphatic system. One of the chemicals shown to make that journey, TiO2, has been linked to inflammation and delayed healing when used in tattoos. That's all we know right now.
The next step in the research will be to find patients who've seen adverse effects from their tattoos and look for links to the chemical and structural properties of the pigments in their body. It's pretty surprising we don't already know this, given that tattooing has been around for thousands of years. But scientists are just beginning to understand what happens at the very smallest level when a tattoo gets under your skin.
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