Absorption, distribution, metabolism and excretion of tattoo colorants and ingredients in mouse and man: the known and the unknown.

During tattooing, high amounts of tattoo colorants, which usually contain various substances, are injected into skin. The major ingredient in tattoo colorants is the coloring component, which can be assigned to two different groups. First, amorphous carbon particles (Carbon Black) are found almost exclusively in black tattoos. Second, tattooists use azo and polycyclic pigments to create nearly all colors of the visible spectrum. Due to their different chemistries, those tattoo colorants usually contain various compounds, such as by-products and impurities. Professional tattooists inject the colorant mixture into skin using the solid needles of tattoo machines, and studies have shown that about 2.5 mg of tattoo pigment is injected to stain about 1 cm(2) of skin. Animal experiments revealed that about one-third of that amount disappeared from skin within weeks after tattooing, and this finding was confirmed by pigment extraction from long-existing tattoos. It is assumed that some of the tattoo colorants stay in the skin because the pigment particles are insoluble and too large to be transported. The other part of the tattoo colorants shows up at least in the lymph nodes located next to the tattoo. To date, no investigations determining whether and to what extent tattoo colorants can be found in any other organs of the human body have been performed. Thus, tattooing of colorants into skin entails a complex reaction of the skin that triggers the immune system and launches manifold transport processes, which might pose additional health risks not only to skin but also to other organs of humans.