The tiny particles, measuring a few millionths to a few billionths of a centimetre, include molecules from preservatives and contaminants such as nickel, chromium, manganese and cobalt, researchers from the European Synchrotron Radiation Facility in Grenoble, France, reported in the journal Scientific Reports.
Tattoo colouring is composed of various organic and inorganic pigments, and can be contaminated with toxic impurities.
Besides carbon black, the second most common ingredient used in tattoo inks is titanium dioxide, a white pigment also used in food additives, sunscreens and paints.
The chemical has been associated with delayed healing, itching and skin irritation.
Scientists in Grenoble, joined by colleagues at the German Federal Institute for Risk Assessment in Berlin, used X-ray fluorescence measurements to identify particles in the skin and the lymph nodes.
The researchers also used a technique called Fourier transform infrared spectroscopy to assess changes in tissue near tattoo particles at the molecular level.
They reported "strong evidence" for both the migration and long-term deposit of toxic elements in the body.