Toxic nanoparticles in tattoo ink don't stay put in the skin; they travel around the body and build up in the lymph nodes, scientists have found.

The nodes are part of the lymphatic system, which helps clear out toxins and transport white blood cells around the body. The nodes act as filters for pathogens and harmful substances. A build-up of toxic nanoparticles from tattoos could lead to lifelong chronic stress on the lymphatic system.

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An X-ray fluorescence investigation has now allowed scientists at the European Synchrotron Radiation Facility to map where toxic compounds from tattoo ink travel to in the skin and the lymphatic system. The results are published in the journal Scientific Reports.

"When someone wants to get a tattoo, they are often very careful in choosing a parlour where they use sterile needles that haven't been used previously," said study author Hiram Castillo.

"No one checks the chemical composition of the colours, but our study shows that maybe they should."

London International Tattoo Convention
Lasse Risvik poses at the International London Tattoo Convention. Neil Hall/Reuters

The body tries to 'clean' the site of the tattoo, removing nanoparticles of the ink via the immune system. These particles build up in the lymph nodes, which act as hubs for the immune cells.

"The lymph nodes become tinted with the colour of the tattoo," said Bernhard Hesse, also a study author. "What we didn't know is that they do it in a nano form, which implies that they may not have the same behaviour as the particles at a micro level."

This is a problem, the scientists say, because the properties and reactivity of many of these nanoparticles is very poorly understood. As such, the health risks that come with having large quantities of these particles in the body are still unknown.

The main ingredient in most tattoos is carbon black, followed by titanium dioxide, which has a white colour used for shading. White tattoos and those including large quantities of titanium dioxide tend to heal more slowly as titanium dioxide irritates the wound. Tattoo ink often also contains traces of nickel, chromium, manganese and cobalt.

Next the scientists plan to find out how the pigments and heavy metals travel to more distant internal organs and tissues.