Tattoo health and safety regulations tend to focus on short-term risks like infections, but little is actually known about the long-term risks of living with ink under your skin, according to a new review in The Lancet. 

“Almost everybody these days has a tattoo, and nobody is talking about the side effects of ink deposits,” said senior author Dr. Andreas Luch of the German Federal Institute for Risk Assessment in Berlin.

“There is no proof that these ink ingredients are safe, being injected into the body,” Luch told Reuters Health.

Between one and five percent of tattooed people suffer a bacterial infection, and some people can have allergic reactions to the ink, according to the report.

Those are short-term effects. It is harder to measure the long-term effects of ink since tattoo inks are in most countries classified as cosmetics, Luch said.

Since the inks are classified as cosmetics, their long-term toxicology can’t be tested in animals, Luch said. In his opinion, tattoo inks should be a completely different product category.

The skin barrier effectively keeps surface cosmetics out of the body, he said.

But tattoo ink is injected into living tissue, which contains blood vessels, nerves and immune cells.

“We need to assume that all of these ink ingredients, including preservatives, processing aids or whatever, will become systemically available in the body over time,” Luch said. “Regulation based on cosmetics is insufficient.”

Examining the bodies of the deceased who have had tattoos for decades has shown that up to 90 percent of the ink has disappeared from the skin, he said.

“We cannot answer the question what is going to happen with these inks,” whether they accumulate in organs over time or are excreted, Luch said.

Similar questions remain for laser tattoo removal: when the pigments are fractured and fragmented under the skin - where do they go – he added.

“In the U.S. the (Food and Drug Administration) has the authority to regulate inks, but is not currently doing so,” said Dr. Michi Shinohara, a dermatologist at the University of Washington in Seattle who was not involved in the review.

“Regulation of tattoo parlors and tattoo artists is left to the states, and the requirements for operating vary widely from very minimal (bloodborne pathogen training) to fairly complex (hundreds of hours of apprenticeship),” Shinohara told Reuters Health by email.

There are no industry standards for ink ingredients, the industry is minimally regulated, and few problems with tattoos are reported to authorities, she said.

Modern tattoo inks mostly contain organic pigments, but can also include preservatives and contaminants like nickel, arsenic and lead, Luch and his coauthors note. In one study in Switzerland, preservatives banned for use in cosmetics were found in 14 percent of tattoo ink samples.

Reactions tend to be more common from colored inks than from black and white ones, Luch said.

Tattooing has been going on for at least 5,000 years, but has become a modern trend, with roughly 120 million people in the western hemisphere having at least one tattoo, Luch said.

“The acute risks are well known,” including pain, bleeding, infection and allergic reaction, Luch said. “The tattooist at least needs to explain that something like this could happen,” he said.

But long term risks, like organ toxicity or cancer, are still unknown, he said.

“It’s an individual decision, we cannot tell someone not to get a tattoo,” Luch said. “I wouldn’t like to have a tattoo on my skin, but if a person likes colored skin, what can I say?”

It’s not necessary for people to stop getting tattoos, Shinohara said, “but I think people should be smart about it - research the parlor, ask about any recent problems, follow the aftercare instructions and report immediately to the tattoo artist and a physician for any problems that occur after tattooing.”