What's In A Tattoo? : Short Wave Three in 10 people in America have a tattoo, and those in the 18 - 34 age bracket, it's almost 40 percent. But what's in those inks, exactly? NPR science correspondent Nell Greenfieldboyce talks about what researchers currently know about tattoo inks. It's not a lot, and researchers are trying to find out more.

Email the show at ShortWave@npr.org.

What's In A Tattoo? Scientists Are Looking For Answers

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You're listening to SHORT WAVE...


SOFIA: ...From NPR.

Maddie Sofia here. And today, we are talking with NPR's Nell Greenfieldboyce about tattoos. All right, Nell, spill it. You got a tattoo? Got a tat?

NELL GREENFIELDBOYCE, BYLINE: I do not. I do not. I have thought about it.

SOFIA: Yeah. So have I. I don't have any, but I kind of have this long-term plan for, like, a whole evolution-y sleeve one day - you know, maybe start off with some single-celled organisms, make our way through evolutionary time, that kind of stuff.

GREENFIELDBOYCE: I'm kind of surprised that neither of us has a tattoo because surveys show that these days there's a tattoo on about a third of all Americans. And among your demographic, Maddie, people aged 18 to 34, it's 40%.

SOFIA: Yeah.


SOFIA: Right.

GREENFIELDBOYCE: So it's pretty common. And as tattoos are more common, scientists are getting more and more interested.

SOFIA: OK, so when you say scientists are getting more interested in tattoos, Nell, like, what is there to be interested in? I feel like tattoos have been around for, like, thousands of years. I remember reading about tattooed mummies. So don't we pretty much, like, know what a tattoo is by now?

GREENFIELDBOYCE: That's what I asked John Swierk. He's a chemist at Binghamton University. And I saw he'd gotten this grant from the National Institutes of Health to study tattoo inks. And he told me that he got interested in tattoos in a kind of roundabout way. And as he started looking into the scientific literature...

JOHN SWIERK: I realized that our basic understanding of tattoos was really kind of limited, particularly from a fundamental science perspective.

GREENFIELDBOYCE: I asked him, you know, what is still unknown? And he was like, well, almost everything.

SWIERK: So the whole kind of picture right down to what a tattoo actually looks like in the body is still a surprisingly open research question.


SOFIA: So today on the show, the scientific mystery that is the tattoo - what researchers know and what they want to know. I'm Maddie Sofia, and this is SHORT WAVE from NPR.


SOFIA: OK, Nell, you recently visited a tattoo parlor. How did you handle that because, you know, pandemic?

GREENFIELDBOYCE: Yeah. I mostly stay at home, as you know, and social distance incessantly. But I planned my trip so that it wouldn't be more than the amount of risk I normally take while doing something like grocery shopping. You know, I live close, and I wasn't traveling outside my community. I took my own car. I wore two masks. I didn't stay long. You know, I had this long microphone holder, so I didn't have to get super close to anybody.

SOFIA: OK. All right. Sounds like some solid risk reduction thinking. So where did you go?

GREENFIELDBOYCE: Tattoo Paradise here in D.C. And it looks just like you'd think a tattoo shop would look. I mean, there's neon signs in the window that say tattoo. The walls are covered with, you know, hearts and sailing ships and just all kinds of classic tattoo art. The owner is a guy named Matt Knopp. And he took me into a back room. We walked past four people getting tattoos on their backs and chest. They use what's basically an oscillating bundle of needles that they dip into ink.

SOFIA: I did not know. I did not know. So - and I assume everybody was, like, wearing masks and stuff, I hope.

GREENFIELDBOYCE: Absolutely. Matt Knopp had a mask, too. He's a big guy with gray hair and a bushy beard and, of course, tattoos. He said he's not much of a science person, but he's been a tattooer for 20-plus years. And when he was younger, he'd go into a tattoo shop, and the inks were just a mystery.

MATT KNOPP: You know, this was magic (laughter). You know, they poured stuff out of these bottles that, you know, that were wrapped and hidden. And, you know, you wouldn't - you couldn't know what it was. You didn't know where they got it from.

GREENFIELDBOYCE: An artist might brew up their own inks, their own inventions.

SOFIA: So how would they - you know, how would they know that the ink is safe?

GREENFIELDBOYCE: They'd try it on themselves.

KNOPP: And then they would see if there's any kind of reaction. You know, did the - you know, did their skin - you know, did it bubble up? Did it - you know, did it just come out? Did it, you know, cause itchiness and do stuff like that? And that was, you know, your kind of trial and error.

GREENFIELDBOYCE: He says this has always been a self-policing industry, and it still is.

SOFIA: But, Nell, like, in this country, there's the Food and Drug Administration - right? - with, like, a mandate to protect public health by regulating things like food and drugs and medical devices. They don't regulate tattooing?

GREENFIELDBOYCE: Basically, no. The agency treats tattoo ink like cosmetics. It only gets involved when there's a specific complaint about a consumer safety problem. Manufacturers here aren't required to label tattoo inks with a list of ingredients. And with the growing popularity of tattoos, there's now a lot of ink manufacturers making tons of colors. Matt Knopp says an artist can pick and choose.

KNOPP: So maybe, like, red from this company, but you like the green from that company and the blue from that company and, you know, this color from that company. And that's - you know, that's what - nowadays, you have those options.

SOFIA: And he feels confident that they're safe.

GREENFIELDBOYCE: That's what he says, yeah. I mean, his business inks people all day long, and it has for years.

KNOPP: Being in this industry, I don't see anything that's out there that says, [expletive], you need to regulate this stuff. This needs to have - you know, we're having issues. Like, there's - it's not out there like that.

SOFIA: OK, so what do the scientists who look into these products say, Nell? You seem to suggest that there's actually not a lot of research.

GREENFIELDBOYCE: Yeah. And those scientists that have looked into this - there's not a lot - say there's unknowns. I mean, a tattoo artist might never hear about a reaction that happens years later.

SOFIA: I mean, does that happen? Like, is there some sort of delayed reaction that goes on?

GREENFIELDBOYCE: It can happen, yeah. And that's something scientists want to understand. Like, does something in the ink break down over time, maybe from exposure to sunlight? You know, tattoos fade. The chemicals change. You know, because there's so little data, a group of researchers recently went and talked to 300 people in Central Park and just asked them if they'd had reactions to their tattoos.

SOFIA: OK, so not like a big study or anything, just kind of trying to get an idea what's going on.

GREENFIELDBOYCE: Yeah, exactly. And while the majority of people said they didn't have adverse reactions, enough people did to worry the scientists. I mean, some people reported having chronic reactions to the tattoo that lasted for more than four months.

SOFIA: What kind of reactions are we talking about here, Nell?

GREENFIELDBOYCE: Stuff like itching, you know, a scaly appearance, raised skin, swelling or like a combination of all those things.

SOFIA: So are those like basic allergic reactions? Is that normal stuff? Like, walk me through it.

GREENFIELDBOYCE: From a survey like that, you can't know what's going on with them, but people can definitely have allergic reactions, especially to red ink. I talked to Ines Schreiver. She studies tattoo ink at the German Federal Institute for Risk Assessment.

INES SCHREIVER: It is a fact that most allergies right now develop in red color shades.

GREENFIELDBOYCE: Why that is is unclear. I mean, red is not one thing. You can have a ton of different compounds, you know, dozens or hundreds of different things that are all red.

SOFIA: And someone who got a tattoo would have no idea what ink was used, like, I'm guessing in most cases.

GREENFIELDBOYCE: Right. Schreiver and some colleagues recently analyzed skin biopsies, so over a hundred skin biopsies taken from problematic tattoos. And they did find some specific red pigments. But she said maybe it's not the color chemical itself. Maybe it's some breakdown product or some other associated ingredient. They're trying to figure out what the real culprits are here.

SCHREIVER: Then we can go and say, please don't use these.

GREENFIELDBOYCE: Because in Europe, where she is, tattooing is regulated. It was country by country, but now, over the next year, it's being harmonized across the European Union. And manufacturers have to label what's in the inks. They have to limit certain chemicals.

SOFIA: And what chemicals are limited?

GREENFIELDBOYCE: She told me stuff that's thought to cause cancer or damage DNA or cause allergies. I mean, you can go to the website of a European consumer safety agency and search under tattoo ink, and you'll see dozens of colors from specific brands that were pulled off the market there - you know, all kinds of colors, like red, plum, yellow, black - for stuff like excessive amounts of nickel or cadmium or zinc or arsenic.

SOFIA: Arsenic, wow. OK, I didn't expect that one.

GREENFIELDBOYCE: Yeah, Ines Schreiver told me that some manufacturers might not even know what's in their ink if they buy ingredients that have impurities. At least one study of tattoo inks in Europe found that a lot of the time, the label's list of ingredients was inaccurate. So, yeah, you know, you can have metals like nickel. I mean, people can be allergic.

SOFIA: Right. And it's not like if you're allergic to an earring or a necklace, you can just take it off, right? It's not the same situation.

GREENFIELDBOYCE: Yeah. And some metal in a tattoo seems to come not from the ink itself, but from bits of metal that actually come off of the needles during tattooing.

SOFIA: OK, OK. All right, so we've talked about the process. We've talked about the ink situation. Nell, what do we actually know about how the cells in our body react to a tattoo?

GREENFIELDBOYCE: Not much. I mean, that guy, John Swierk, I talked to at Binghamton University, he said with tattoo ink, we're basically talking about dyes and little bits of solids that can be held together with plastics.

SWIERK: The body really just does not have a lot of tools that are capable of digesting and metabolizing those things. And so we think that the solution is just to isolate it and keep it away from everything.

GREENFIELDBOYCE: But that isolation isn't a perfect thing. I mean, it's been known for a long time that tattoo pigments show up in the lymph nodes. So, like, if you biopsy a tattooed person's lymph nodes, they can look dyed, you know, colored.

SOFIA: I mean, that's wild. That's wild.

GREENFIELDBOYCE: It's only recently, like in the past few years, that scientists have even figured out what cells in the skin deal with tattoo pigments. There are these immune cells called macrophages.

SOFIA: That makes sense. I mean, macrophages are good at, you know, detecting and eating up foreign stuff in the body.

GREENFIELDBOYCE: Well, studies in mice show that these cells in the skin capture and retain large amounts of tattoo pigment. And when these cells die, they release that pigment into the immediate surroundings, where it eventually gets taken up by new macrophages. There's this constant turnover.

SOFIA: I mean, that's pretty cool. I mean, you know I'm an immune system fan, Nell. You know that about me. Because, you know, I think of tattoos as this kind of unchanging thing, but that actually sounds really dynamic. Like, you know, the immune system doesn't sleep on you, Nell.

GREENFIELDBOYCE: Sure. It's like capture, release, capture, release. This could be going on for decades. I mean, at least that's what scientists think. There, you know, is not a ton of research here.

SOFIA: Yeah. I mean, I'm definitely getting that impression from all of this. OK, so besides local reactions in the skin, is there any evidence linking tattoos to more general health issues?

GREENFIELDBOYCE: I talked with this dermatologist at Northwestern University, Walter Liszewski, who treats tattoo reactions. He's also a cancer epidemiologist who works with national datasets. And he told me that no one really collects data on tattoos. And there's just so many different variables, like how much body area is covered for how many years with what kind of ink.

WALTER LISZEWSKI: I would love some way to get data to really look and see if there's an association between malignancy and tattoos. But there's just multiple layers of data that we don't have and complexities that make it very, very difficult.

GREENFIELDBOYCE: There are researchers in Europe who are trying to do those kinds of studies now, though.

SOFIA: Does it - I mean, does it seem like the U.S. might go the way of Europe and start regulating tattooing?

GREENFIELDBOYCE: There has been proposed legislation. Some tattoo supply companies banded together in this thing called the Coalition for Tattoo Safety to sort of lobby against it. I mean, in Europe, the regulations can be controversial. Schreiver told me Europe is currently phasing out two widely used blue and green pigments. And apparently, some tattoo artists are not happy.

SOFIA: I mean, when you talked to Matt from Tattoo Paradise, what did he think about all this?

GREENFIELDBOYCE: Matt Knopp says, you know, if there's going to be tattoo ink regulations in the U.S. ever, I mean, he would just hope that it's done in partnership with tattoo artists so that, you know, whatever is put in place makes sense, that it's not some kind of witch hunt.

KNOPP: Witch hunts destroy businesses and industries when, you know, when it's done by people that don't understand what they're getting into.

GREENFIELDBOYCE: He means, you know, like just slapping regulations on something without understanding all the consequences.

SOFIA: Yeah, OK. I mean, that makes sense. Did he give you the sense that people who get tattoos pay much attention to the ink that's used?

GREENFIELDBOYCE: He told me people usually don't ask. Anyone can go online and buy tattoo ink from places like Amazon.

SOFIA: Oh, yeah. Like for home tattooing, right?

GREENFIELDBOYCE: Yeah, yeah. One of the things that scientist John Swierk is doing is trying to build a public database. He wants to basically analyze a whole bunch of commercially available inks and put that information out there so that, you know, anyone who wants to can look at it and make their choices.

SOFIA: OK, Nell, I mean, this is - you know, the overwhelming feeling I get is not necessarily like that tattoos are bad or, you know, generally unsafe. It's just, you know, that there's a lot of questions out there, and we don't actually have that much data. I mean, how should we think about it?

GREENFIELDBOYCE: You know, when I talked to these researchers, you know, some of them basically made the point that they know that tattoos are deeply meaningful to a lot of people. Like, you know, it's something very personal that you're doing with your own body. It's a form of artistic expression. And I think the researchers I talked to, you know, they're not trying to, like, vilify tattoos or, like, make people scared of tattoos. They're just trying to understand, OK, like, what are people putting in their bodies? You know, what is the consequences of that? And, like, let's make sure that it's as safe as possible and that there really may need to be, like, some more science on some of this stuff to even understand that.

SOFIA: All right, Nell, well, thank you for this quick tour into the science of tattoo ink and how tattoos are in our body. I honestly had no idea about a lot of this. So lots to think about planning my sweet, sweet tat, you know?

GREENFIELDBOYCE: I look forward to seeing it, Maddie.


SOFIA: This episode was produced by Thomas Lu, edited by Gisele Grayson and fact-checked by Rasha Aridi. The audio engineer for this episode was Josh Newell. I'm Maddie Sofia. Thanks for listening to SHORT WAVE from NPR.

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