FDA Study Finds Bacteria in One-Third of Tattoo Inks

Tattooing has been practised by people for thousands of years.

We use needles to place images and symbols that matter to us on our bodies, piercing the protective skin barrier to introduce ink that remains permanently lodged just beneath the epidermis.

Naturally, this process should not also introduce potential pathogens. Although sterilisation standards in the tattoo industry have improved in recent years, a 2024 US Food and Drug Administration study produced a concerning result: a batch of 75 sealed tattoo and permanent makeup inks was tested, and one-third contained bacteria, including some that can cause illness in people.

The researchers have now taken a broader look to establish whether that result was unusual.

FDA analysis of tattoo ink contamination

Their retrospective analysis combined four FDA investigations of tattoo ink carried out from 2018 to 2024. Of the 259 unopened containers of tattoo and permanent makeup ink examined, one-third contained bacteria. In total, the team recovered more than 250 bacterial isolates spanning 94 species, including several recognised human pathogens.

In other words, the 2024 findings were not a one-off.

"These findings underscore that microbial contamination in tattoo and permanent makeup inks is widespread and diverse, reinforcing the need for sensitive molecular detection methods, expanded surveillance, and harmonized manufacturing standards to ensure product safety," writes a team led by FDA microbiologist Ohgew Kweon in a paper published in Scientific Reports.

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All four individual FDA surveys indicated that ink contamination is a real issue, including in inks sold with sterile labels.

However, each investigation had examined a specific group of products using its own approach. This left unresolved questions about how frequently contamination occurred across the studies, whether particular product features could predict it, which microbes repeatedly appeared, and how much bacterial diversity had yet to be identified.

Perhaps the most important outstanding question was where, and by what route, the inks became contaminated.

These were the gaps in knowledge that the researchers aimed to fill.

They combined the previous surveys into a sample of 259 unopened tattoo and permanent makeup inks, covering different brands, colours and sterility claims.

For the original testing, the inks were opened in laboratory conditions. Genetic sequencing was then used to identify bacteria in colonies grown from the samples. This meant the results did not merely indicate tiny amounts of bacterial DNA: the bacteria were alive and capable of growing into colonies.

For the new research, the team applied one consistent analytical framework to the combined results, enabling patterns to emerge that none of the separate datasets could have revealed alone.

Although contamination levels differed considerably across the four surveys, the pooled estimate for bacterial contamination across all studies was 35.4 percent.

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Sterile tattoo ink labels offered little assurance

One result was especially notable.

A sterile label was of limited value as an indicator of true sterility. Of the 118 samples labelled sterile, almost one-third - 30.5 percent - were contaminated. That compared with 35.5 percent among products that made no sterility claim.

Neither the ink's type nor where it came from provided reassurance. Bacteria were found in 33.3 percent of tattoo inks and 33.0 percent of permanent makeup inks. Likewise, 33.5 percent of US-made inks were contaminated, compared with 31.9 percent of imported inks.

Whichever comparison was made, the figure came to roughly one-third.

More concerning still was the identity of the bacteria. The team detected 94 species across 38 genera, with Bacillus by far the most common. It was followed by Pseudomonas, Staphylococcus and Lysinibacillus.

Of the 94 species, around one-third - 34 - are classed as potential pathogens because of documented links to human disease. They include Pseudomonas aeruginosa, Bacillus cereus and Cutibacterium acnes.

This does not mean that every contaminated ink will cause an infection. The study found bacteria capable of causing disease, but did not assess whether the contaminated products had actually made anyone ill.

Good hygiene standards in the studio can minimise infection risks. (Alvaro Medina Jurado/Moment/Getty Images)

"These findings are consistent with documented infection events and product recalls associated with microbial contamination introduced during ink manufacturing or distribution," the researchers write.

The full scale of bacterial contamination remains uncertain

The 94 recorded species may not, however, capture the problem in its entirety.

As sample numbers rose, so did the number of bacterial species detected. Although the rate of increase slowed, the curve did not level off, meaning that a larger sample could uncover further bacteria.

The research was also restricted to species that can readily grow in culture. Bacteria that grow slowly, have demanding requirements, or are viable but non-culturable may not have been detected.

For instance, several outbreaks of tattoo-associated nontuberculous mycobacterial infection have been reported. The bacteria responsible can need specialised growth media and longer incubation periods than those used in these surveys.

The study also cannot establish when contamination happens or how it enters the products. Sterility claims did not reliably predict contamination, nor did ink type, colour or country of origin.

There is no clear measure available to consumers - or even tattoo practitioners - that would allow someone to inspect a bottle of tattoo ink and determine whether it is safe.

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The researchers say their findings point to deficiencies in existing manufacturing and quality-control practices. Their analysis indicates that validated controls and sterilisation processes are needed during manufacturing.

"These findings underscore the need for improved manufacturing quality control, validated sterilization procedures, and enhanced microbiological surveillance using complementary culture-based and molecular approaches to strengthen microbial risk assessment and improve the safety of tattoo and PMU ink products," the researchers write.

For anyone thinking about getting a tattoo, though, the guidance remains largely unchanged. Thoroughly research the artist. An artist who follows rigorous hygiene procedures and monitors ink recalls and package integrity is likely to be safer than your mate Jim's friend using a tattoo gun in his garage.

The findings were published in Scientific Reports.

This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we take pride in our process, we are only human. If you notice an error, please let us know.