Background Tattooing entails the injection of high amounts of colourants into skin. Excepting black inks, red azo pigments are the most frequent colourant used. Part of the pigment is transported away via lymphatic system. Another part can be decomposed in skin, which might be responsible for many known adverse skin reactions.
Objective The aim of this study was to estimate the extent of decomposition and transportation by measuring the decrease of pigment concentration in human skin under in vivo conditions.
Methods Red pigments were extracted from nine tattooed skin specimen and attempted quantification by using HPLC technology. To optimize quantification, we synthesized five common red azo pigments with purity at 98% and used them as HPLC reference substances.
Results In five of the nine skin specimens, we were able to identify and subsequently to quantify the red tattoo pigments such as Pigment Red 22 or Pigment Red 112. The mean pigment concentration in skin was 0.077 ± 0.046 mg/cm². As the pigment concentration in skin ranges from 0.60 to 9.42 mg/cm² (mean: 2.53) directly after tattooing, we estimate a decrease of 87 to 99% of pigment concentration in skin after tattooing.
Conclusion Millions of people have many and large tattoos, whereas a single tattoo frequently covers a skin area of more than 300 cm². Thus, the major part of more than 760 mg of azo pigments either decomposes in skin or migrates in the body. That may pose a health risk on tattooed individuals, in particular may cause severe skin reactions.