Earlier this month I stumbled on an article in Mic, an online magazine aimed at millennials, that discussed the possible role of tattoos in “boosting the immune system” (which you can’t do) and reducing your risk of catching a cold. I am not a millennial, but thankfully I was still able to access and read the content. It was terrible in a well-meaning sort of way, and a great example of why dedicated science and medicine journalists are best suited for discussing these issues.
The author of this particular article is a yoga instructor. Not that there is anything wrong with that, of course. My wife is a certified yoga instructor. She just also happens to be quadruple boarded in pediatrics, pharmacology, pediatric oncology, and palliative medicine. Neither of us have any tattoos.
Speaking of tattoos, what do they have to do with the immune system or your risk of viral infections? Probably nothing at all. Well, almost certainly nothing at all. The whole concept, as I will discuss in absurd detail considering how silly it is, is absurdly silly. There is a tiny sliver of plausibility, and now two studies, but this is very unlikely to result in anything other than an Ig Nobel Prize.
But before I discuss the current article, we need to go all the way back to 2016. 2016, the year the Chicago Cubs broke the curse of a goat, or Babe Ruth, or something like that. Russia interfered with our elections. Oh, and Brexit. Also in 2016 there was a slurry of articles about tattoos preventing the common cold, like this one.
In March of that year, a study authored by Christopher Lynn and a team of anthropologists from the University of Alabama was published in the American Journal of Human Biology. It investigated a link between tattoos and immune function. Lynn was working from the personal observation that getting a tattoo seemed to make people feel tired and more likely to become ill. He further hypothesized that any negative effect on immune function would be reversed as more tattoos were accrued over time, and that there might actually be a beneficial response.
In the above linked Science Daily article, he is quoted likening this to the difference between someone who is out of shape going to the gym once, and someone partaking in regular exercise:
“After the stress response, your body returns to an equilibrium,” Lynn said. “However, if you continue to stress your body over and over again, instead of returning to the same set point, it adjusts its internal set points and moves higher.”
Though perhaps intuitively satisfying, this is nonsense from a medical standpoint. His use of the concept of stress is so nebulous that it renders this statement uninterpretable. He is trying to say that regular exercise, particularly of moderate intensity, is good for you and better than just occasionally hitting the gym. This is true in a variety of ways, including when it comes to immune function, but equating that to getting tattoos doesn’t make much sense.
Lynn recruited a convenience sample of 29 adult subjects, almost all women, with varying degrees of tattoo experience. He obtained saliva samples both before and after each subject got their planned tattoo in order to measure levels of cortisol and secretory immunoglobulin A (SIgA) as surrogate markers for stress and immune function respectively. Obviously the immune system and the human response to stress is extremely complex and involves many more factors than this, but cortisol and SIgA are easy to measure in saliva and these were anthropologists, after all, not medical researchers.
Before we get to the results, a quick and basic primer on IgA:
IgA is the most abundant antibody type in our bodies, and its secretory form is particularly prevalent in saliva and mucous secretions in the respiratory, GI, and genitourinary tract. This form is produced locally in mucous tissue rather than in the bone marrow where other immunoglobulins, including serum IgA, are made. Unique SIgA is produced in response to exposure of mucosal tissue to different microbial antigens, thus they provide protection from future infections largely by coating pathogens and preventing them from penetrating the mucosal surface.
There is much more to IgA, but for our purposes today that is about all you need to know. IgA clearly plays a role in preventing infections such as the common cold, among many others, but it isn’t quite that simple. A lot of people are deficient in the stuff, but because there are many redundant immune functions the vast majority, around 90% in fact, don’t have more infections. And in the 10% of IgA-deficient patients who do develop more infections, they don’t tend to be more severe. And this is over a lifetime of having no IgA. So the notion that transient changes in SIgA levels in response to acute stress might alter your risk of catching a cold is not well supported.
Now back to our study. I was unable to obtain the full paper, and the abstract linked to above was unfortunately not very helpful. But based on it and the numerous articles published at the time, it looks like they found that getting a tattoo was associated with a decrease in SIgA levels, but less so in subjects with more previous tattoo experience, and all results were within the normal range. Again, not that that really matters in this context.
This could have just been random fluctuation in an underpowered study. Noise, essentially. And who knows how long any changes in SIgA lasted after the tattoo session? Once again, not that it matters…at all. There is very little reason to expect a clinically meaningful difference in the risk of catching a cold when SIgA levels are a little lower. The authors attempted to link the drops in SIgA to stress, which is why they measured salivary cortisol levels, but I was unable to find any mention of those results. It was implied, however, that there was an inverse relationship with more experienced subjects having less of a stress response with repeated tattoo sessions.
It’s important to point out that cortisol levels vary significantly depending on the time of day. It does not appear that this was taken into account. The bottom line is that it was ridiculous in 2016, based on this study, to conclude that tattoos play any role whatsoever in the function of the human immune system regardless of how many you get.
Now lets fast forward to October of 2019 and see if there is reason to update this assessment based on new data. Here again is the Mic article that first got my attention. It starts by repeating the implausible and unfounded conclusions made in 2016:
Tattoos are wounds and when your body is hurt, your immune system swoops in like a cellular superhero that fights infections in not just the tattoo, but throughout the whole body.
This is wrong on many levels. Remember, the 2016 study found that SIgA levels decreased in all subjects, just less so in those with more tattoo experience. The implication was that more experienced subjects were less stressed and thus had lower cortisol levels, which had less of a negative effect on immune function. This does not mean that the overall function of their immune system was improved or that they would be less likely to get sick. Also, that study was garbage and didn’t tell us anything about cortisol levels in relation to getting a tattoo, and it isn’t even clear that cortisol spikes would change SIgA levels.
I’m going to move on from the Mic article now. More helpful in this discussion is the article in The Conversation which it was based on, and that was written by Christopher Lynn himself. In it, he discusses the details of his attempt to replicate the 2016 study in a population of American Samoans. The new study was published last month, again in the American Journal of Human Biology, which apparently is a respected publication.
I’m going to quote liberally here.
He starts off with a reference to his 2016 study:
This field season was the fourth of my research on the relationship between tattooing and immune response. My first study had focused on a small sample, mostly women, in Alabama. What I’d observed among that group suggested that tattooing could help beef up one’s immune response.
No, it didn’t. It suggested that randomly checking salivary SIgA levels yields random results.
He then demonstrates some admirable insight:
But one small study in the United States wasn’t proof of anything – despite headlines blaring that tattoos could cure the common cold. Good science means finding the same results multiple times and then interpreting them to understand something about the world.
Yes…sort of. Good science means attempts to replicate results after taking into account flaws in the design methodology of earlier studies and the prior plausibility of the hypothesis in question. In this case, replication with just another small study, particularly one that is needlessly complicated by aggressive statistical processing, just wouldn’t be enough.
He follows with an incredible leap in logic:
Tattooing creates a permanent image by inserting ink into tiny punctures under the topmost layer of skin. Your body interprets a new tattoo as a wound and responds accordingly, in two general ways.
Innate immune responses involve general reactions to foreign material. So getting a new tattoo triggers your immune system to send white blood cells called macrophages to eat invaders and sacrifice themselves to protect against infection.
Your body also launches what immunologists call adaptive responses. Proteins in the blood will try to fight and disable specific invaders that they recognize as problems. There are several classes of these proteins – called antibodies or immunoglobulins – and they continue to circulate in the bloodstream, on the lookout lest that same invader is encountered again. They’re at the ready to quickly launch an immune response the next time around.
This adaptive capacity of the immune system means that we could measure immunoglobulins in saliva as approximations of previous stress caused by tattooing.
Wait…what? There is no connection whatsoever between skin wounds and the production of salivary SIgA levels. As I discussed above, SIgA is only produced locally in the mucous membranes as a result of exposure to pathogens on those surfaces. And what does stress have to do with that process? Nothing. That last sentence is garbage.
He discusses the new study, which involved 25 subjects that were mostly tourists visiting American Samoa:
We collected saliva at the start and end of each tattoo session, controlling for the tattoo duration. We also measured recipients’ weight, height and fat density to account for health. From the saliva samples, we extracted the antibody immunoglobulin A, as well as the stress hormone cortisol and inflammatory marker C-reactive protein. Immunoglobulin A is considered a frontline immune defense and provides important protections against frequent pathogens like those of the common cold.
By comparing the levels of these biological markers, we determined that immunoglobulin A remains higher in the bloodstream even after tattoos heal. Furthermore, people with more time under the tattoo needle produced more salivary immunoglobulin A, suggesting an enhanced immune response to receiving a new tattoo compared to those with less or no tattoo experience. This effect appears to be dependent on receiving multiple tattoos, not just time passed since receiving one. This immune boost may be beneficial in the case of other skin injuries and for health in general.
So in this small study, they found that some of the subjects had higher levels of SIgA after getting a tattoo. Remember, in the previous study they all had decreased levels. This supports the notion that it’s all just random noise rather than that the immune system was somehow boosted. The claim that elevated SIgA levels, even if directly caused by the tattoo, would play a role in non-mucosal surface healing or general health goes against the basic scientific understanding of what these antibodies actually do in our bodies.
He goes on, quite a bit more in fact, but doesn’t say anything that is really different from what I’ve covered. He does at one point imply that getting tattoos is similar to being vaccinated. Yikes. And he does reveal that he is in the middle of another study, this time involving 50 subjects. He has collected more saliva samples which will be used to help him understand something about the world I suppose.
I have nothing against Lynn. And what a cool job, am I right? He gets to travel and hang out in tattoo parlors. He’s just way out of his element when it comes to the medical sciences. It’s hard to wrap my head around why there are anthropologists studying the immune system without any apparent input from a relevant expert. It’s like they just googled it one day.
Tattoos are fine, although not risk free. Make sure that you are going to a reputable establishment that follows proper safety protocols. And don’t expect that they will protect you from catching a cold no matter how many you get.