• azo dye;
  • laser - mutagenicity;
  • tattoo


  1. Top of page
  2. Abstract
  3. References

Abstract:  Decorative tattoos have become a common feature of many societies. Their popularity appears mainly driven by fashion, and scant attention has been paid to any associated risk. The risks can be associated either with the tattooees’ proclivity for risk taking in general, or with the substances used in the tattoos.

It is well established that tattoo pigments wander widely in the body after they have been injected, and research now suggests that azo pigments may become mutagenic after exposure to either natural light or laser light. This may not only affect the risk profile of tattoos themselves, but also tattoo removal using lasers.

Tattoos have long cultural history worldwide and have been used since prehistoric times. Oetzi, a 6000-years-old mummy found in the Alps had 39 tattoos (1). In traditional societies they are often associated with life transitions, initiation or health. Historically, tattoos have also been seen to have a protective aspect, such as the traditional sailors’ tattoos of a pig on one foot and a rooster on the other, which were thought to protect the wearer from drowning (1). In a less metaphysical and more secular/decorative manner tattoos are increasingly common in the Western world, for example, when being displayed prominently by younger people’s role models from the entertainment industry. It is thus estimated that almost one quarter of the US adult population has a decorative tattoo (2). In spite of this big number, little attention has been paid to the many complications that can arise from tattoos. These range from simple inflammation and infections to neoplasms directly associated with the tattoo (3–7). In addition, specific tattoos can be seen as a marker of a proclivity to risk-taking or frank psychosocial problems suggesting a secondary or broader associated complication (8). Finally, the tattoo pigment has changed with changing demand for lustre and colour.

In this issue of Experimental Dermatology, Dr Engel and her co-workers address the issue using a mouse model to study the distribution and composition of tattoo pigment following UVR and laser treatment. The authors argue that there may be a risk of complications either over time or due to attempts to remove the tattoos with lasers and that this risk derives directly from the pigment used and its movements in the body. A range of pigments is available today: Classical, biochemically inert substances such as carbon; and more recently, azo yellow ink (discussed here) organo-metallic red inks and white titanium oxide nanoparticles. The movement of tattoo pigment is well known, not only from clinical observation of old tattoos which can achieve a pale ‘washed-out’ look over time but also from imaging studies. Using in vivo confocal microscopy, optical coherence tomography and PET scanning the drift of pigment can be visualized (9–11). The pigment can spread locally to adjacent skin or mucosa, and tattoo pigment has been found in lymph nodes of melanoma patients simulating metastasis and suggesting that it may wander widely in the body (12–14). Although Dr Engel and her co-workers did not utilize the mouse model used to study this phenomenon further in this study there is no doubt that the model is appropriate and can answer many more questions about the wandering of the pigment over time, as well as giving more precise estimates of the absolute amounts of pigment or its metabolites. It does however also raise a number of questions which would need attention in future studies: The differences between mouse and human skin in thickness and optical qualities, which aspects of the solar spectrum act on which pigment, the time elapsed between tattooing and irradiation, the difference between inks, does sunlight trigger decomposition only or is migration also involved?

The other aspect of this problem is what wanders. Tracking inert harmless pigment such as, for example, carbon would be of less interest, but it has been suggested that tattoo azo pigments may become mutagenic following either solar or laser light irradiation (15–18). Even simple metals are however also modified by laser irradiation and may therefore require additional investigation (19,20). The authors describe an impressive 60% pigment reduction after 32 days of simulated solar radiation in their experiment and speculate that this reduction may be due to decomposition of the pigment in the skin. The possibility of redistribution is not exhausted in the study. Apart from obviously suggesting the possibility of tattoo removal through simple solar irradiation, this brings up the question of toxicity not only locally in the skin but systemically as well (21). Potentially hazardous decomposition elements of the PR22 pigment used, were used (2,5-MNA and 4-NT) however only found after ex vivo laser therapy of the tattooed skin and not in the in vivo solar radiated skin. The experiments described therefore do not show that the same effect occurs in vivo. It has been estimated that nearly one-fifth of the tattooees wish to have their tattoos removed (22). This most often involves laser treatment, and it may therefore be speculated if this is the most appropriate form of therapy. According to the present data, laser therapy of tattoos could be interpreted to represent a potential health hazard in itself. In the experiment by Dr Engel it can be estimated that the animal were on average exposed to an estimated 47 μg of 2,5-MNA and 4-NT. It would have been helpful to know if the levels of the hazardous amines approach biologically meaningful levels as implied in the study.

The role of the tattoo has changed over time. In becoming a secular decoration, the tattoo appears to have lost its protective powers. Further studies will show to what degree protection has been replaced by danger.


  1. Top of page
  2. Abstract
  3. References