Ultraviolet radiation (UVR) induces
skin cancer. The combination of UVR and red
tattoos may be associated with increased risk of
skin cancer due to potential
carcinogens in
tattoo inks. This combination has not been studied previously. Immunocompetent C3.Cg/TifBomTac hairless mice (n=99) were tattooed on their back with a popular red
tattoo ink. This often used ink is banned for use on humans because of high content of the potential
carcinogen 2-anisidine. Half of the mice were irradiated with three standard
erythema doses UVR thrice weekly. Time to induction of first, second and third
squamous cell carcinoma (SCC) was measured. All UV-irradiated mice developed SCCs. The time to the onset of the first and second
tumor was identical in the red-tattooed group compared with the control group (182 vs 186 days and 196 vs 203 days, P=ns). Statistically, the third
tumor appeared slightly faster in the red-tattooed group than in the controls (214 vs 224 days, P=.043). For the second and third
tumor, the growth rate was faster in the red-tattooed group compared with the control (31 vs 49 days, P=.009 and 30 vs 38 days, P=.036). In conclusion, no spontaneous
cancers were observed in skin tattooed with a red ink containing
2-anisidine. However, red
tattoos exposed to UVR showed faster
tumor onset regarding the third
tumor, and faster growth rate of the second and third
tumor indicating red ink acts as a cocarcinogen with UVR. The cocarcinogenic effect was weak and may not be clinically relevant.