Scientists have discovered tattoo particles migrated from skin to the lymph nodes of four human corpses.

Millions of people worldwide are tattooed, including an estimated 20 per cent of Canadians, with higher rates among those aged 18 to 34, yet little is known about the long-term health effects of tattoos.

To start to fill in the gaps in knowledge, researchers from Germany and France used high powered X-ray and other instruments at the European Synchrotron Radiation Facility to analyze tattoo pigment samples from four tattooed corpses and two control donors.

In this week's issue of the journal Scientific Reports, the scientists report finding a range of tattoo pigments in skin. But the smallest nanoparticles, less than one-thousandth the thickness of a piece of paper, tended to be found in the lymph nodes.

Application techniques in tattooing make a difference in allergic reactions, says tattoo artist Ariano Delena. He uses vegan pigments at his studio. (Melanie Glanz/CBC)

The results suggest contaminants remain in the body after a tattoo heals, said Ines Schreiver of the chemical and product safety department at the German Federal Institute for Risk Assessment in Berlin.

"You have a probably lifelong deposition in the lymph nodes," Schreiver said in an interview.

The lymph nodes and glands are part of the immune system and filter foreign substances.

Researchers have long observed the colouring in lymph nodes, but little is known about the fate of pigments deposited under the living layers of skin in people with tattoos.

The movement of pigment particles to lymph nodes is part of the body's normal healing response, Schreiver said.

"What I am trying to do with my research is that people think about the chemistry."

Ines Schreiver, left, conducts experiments with Julie Villanova as part of her research to understand where tattoo pigments move and collect. (B. Hesse/European Synchrotron Radiation Facility)

Contaminants such as the heavy metals chromium and nickel collected in the lymph nodes.

Consumers likely wouldn't know what components or impurities are in the pigments applied by tattoo artists, said Dr. Zaki Taher, a dermatologist in Edmonton and an associate professor at the University of Alberta who has studied tattoo reactions and performs removals.

"I think the biggest thing that this study reveals is there's proof of this transport and collection. In terms of coming to a conclusion about risk, I think it's a little early to make absolute conclusions, so I wouldn't raise alarm bells," Taher said.

"The trouble with raising alarm bells is there could be a panic, and I think it may be an unnecessary panic because for all we know, these collections are walled off and not becoming systemic or causing a toxic reaction."

Health Canada stresses safety

Ariano Delena, co-owner of I Love Mom tattoo studio in Toronto, ​said he has observed how acrylic micropolymer and alcohol content of pigments, as well as application techniques, all make a difference in immediate skin reactions.

"All those brands, we stay away from," Delena said. The studio uses vegetable-based pigments, although some colours fade more quickly.

Health Canada said it is important that the pigment does not contain substances that may be unsafe or cause adverse reactions.

"Cosmetic pigments [or ingredients] are not approved by Health Canada," the regulator said in an email to CBC News.

"It is the responsibility of the manufacturer or importer to meet the requirements of the Food and Drugs Act and Cosmetic Regulations, and ensure that the product they are selling is safe. The same requirements apply to tattoo inks containing nanoparticles."