Humans have been tattooing their bodies for over 5,000 years and seem like the craze for inking is not likely to wear off soon. A survey conducted in 2019 reveals that about 30% of the total population in the US— over 90 million people have at least one tattoo on their body, and these numbers are likely to increase in the coming years. But what’s interesting is that many inked people and even tattoo artists have no idea what’s inside the ink.

One of the major reasons behind the mystery surrounding tattoo ink is that tattoos are still not regulated even in developed countries like the US. Sure, the tattoo ink label contains a list of ingredients, but seeing how there is no real regulation, how reliable are these labels? Turns out that not much, according to a new study.

According to the authors, tattoo ink labels are largely inaccurate, as they may contain pigments that aren’t listed. Moreover, they found some inks contained pigment particles whose size may be dangerous to the human body.

“I think a big reason is that historically tattooing was seen as being taboo. For a large part of the last century, tattooing was very much out of the spotlight and artists would make inks on their own. Some still do actually. While the development of commercial inks has led to more standardization from batch to batch, I think for ink manufacturers, there are concerns about proprietary information, which is another reason to not share information,” lead researcher of thew new study and assistant professor at Binghamton University, John Swierk told ZME Science.

The secret ingredients of tattoo ink

Tattoo ink is typically composed of two primary parts: a carrier solution containing mostly ethanol or isopropanol, and a pigment made of compounds like titanium dioxide (TiO₂), iron oxide, (Fe₂O₃), or barium sulfate (BaSO₄). The researchers highlight that since TiO₂ is inexpensive, gives a bright white color, and is generally considered to be non-toxic, it is the most common tattoo ink pigment material.

However, if the particle sizes (of titanium dioxide pigment) in the ink are less than 100 nanometers, they can cause cellular damage. Some manufacturers also add witch hazel plant extracts and components like ethylene glycol in the carrier solution to help with skin healing and changing the viscosity of the inks respectively. The ink pigment gives the tattoo its color and bright look, whereas the carrier solution enables the ink to settle into the middle skin layer with ease and comfort.  

The researchers examined 100 different ink samples and noticed that many tattoo ink samples contained ingredients that weren’t mentioned on their packaging. These include azo-containing dyes that can break down when exposed to ultraviolet light from the sun or even laser removal and bacteria. Previously, a 2016 report from the Joint Research Center found that azo-containing dyes could release cancerogenic compounds when exposed to the sun.

Moreover, when the researchers investigated 16 ink samples using electron microscopy (an advanced technique used to examine ultra-small structures like body cells and even atoms), eight ink samples were found to be composed of particles having sizes less than 100 nm.

“That’s a concerning size range. Particles of this size can get through the cell membrane and potentially cause harm,” said Swierk. 

The “What’s In My Ink?” initiative

According to the researchers, a big challenge is that there is so much that people and even scientists don’t understand about tattoos in general. Most people are just concerned with the design or color of the tattoo but they don’t think much about the ink. However, tattoo inks are complex mixtures and sometimes they might contain ingredients capable of causing harm to the human skin and body. Although government regulations could bring some transparency, nobody knows when they’ll be implemented. 

Swierk and his team have decided to spread awareness on tattoo ink using the peer-reviewed data from their study. They have set up a website — “What’s in My Ink?”. People interested in tattooing can visit the website and gain valuable insights on tattoo inks and thus make an informed decision.

“Our goal with “What’s in My Ink?” is to help artists and consumers make informed choices. As chemists, we have access to tools that the average person doesn’t, which allows us to really look into inks and evaluate what’s in them. People should be free to make their own decisions but we want to provide them with the best information we can. For example, others have that some inks might contain a high level of chromium or nickel. If you have an allergy to those metals, you would want to know that so that you can avoid those inks,” Swierk told ZME Science.  

The researchers are currently planning to study more commercial inks available in the US market. They also want to analyze the toxicity of pigments on model human skin cells, as well as study the process of laser tattoo removal in order to identify the most efficient frequencies that can break down the ink pigments. 

The findings were presented at this week’s 2022 fall meeting of the American Chemical Society (ACS).