Young, T., Whiteside, T., Locklear, J. 2020. What is your tattoo ink telling you? Laboratory Animal Science Professional 8(2) (March/April), 62-65.

Tattooing traumatizes the skin, which can result in microbial infections with the severity ranging from minor to life-threating septicemia. Additionally, the metals in colored tattoo ink are known to cause dermal inflammation in some people. In the laboratory animal research field, tail tattooing has been widely used for decades as a reliable and clear method for rodent identification. It is used as a unique identifier for recording mouse colony information, health issues, and experimental data. However, this identification method can result in skin inflammation and primary or secondary skin infections. For the last 2 years, sporadic clinical cases of ulcerative, edematous tail dermatitis have been seen in our tattooed sentinel Swiss Webster mouse colony. This is in part due to self-injurious behaviors but may also be caused by bacterial infections and chemical impurities associated with the rodent tattooing supplies and procedures. The purpose of this study is to define mouse tattoo bacterial infections and chemical impurities associated with our current rodent tattooing supplies and procedures. Our results demonstrated that tattooing inks (open, dispensed into a secondary container, and unopen) and tattooing equipment are contaminated with environmental microbes. Our results also demonstrated exceptionally high lead and high arsenic levels in the red ink compared to the blue and black inks. In our study, tattooing with red ink caused an immediate dermal irritation as indicated by mice biting and scratching their tails, which was not observed when using the blue or black inks. This study led to revisions of our rodent tattooing standard operating procedure (SOP) – the SOP is described in this paper.

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