Analytical Chemistry and the Hidden Risks of Laser Tattoo Removal

It might not be obvious from everyday experience, but according to the 2012 Harris Poll, one in five adults in the US has at least one tattoo and 86% of those asked have never regretted getting one. But, what if someone were to have second thoughts and decided to get their tattoo removed? It turns out, that tattoo removal is a technically difficult task, considering that virtually all pigments in use are “permanent” and a tattoo is intended to last a lifetime. The most successful tattoo removal practice to date is the laser treatment, during which the ink is destroyed by heating through light absorption. Given the popularity of tattoos, it is not surprising that the tattoo removal business is a big and growing one and that academic research is always in search of innovation.

Technically speaking, a tattoo is a body modification in which colored ink is inserted into the dermis layer of the skin. Dermis is the “cushion” part of the skin, filled with various fibers, and is responsible for various functions including skin resistance to mechanical stress. During the tattooing process, colored ink consisting of a carrier fluid in which small particles of pigment are dispersed, is loaded into the dermis layer in concentrations up to several milligrams per square centimeter of the skin area. The tattoo laser removal process consists of applying short pulses of light with a wavelength tailored to the pigment absorption, so the pigment particles decompose under the heat supplied by the light. This technique, known as selective photothermolysis, was described by dermatology pioneers Anderson and Parrish in 1983. The main trick behind the technique is to use light pulses short enough, so the heating happens fast enough that the pigment particles cannot dissipate into the surrounding environment. In other words, pigment particles are being selectively burned by the laser. After such a treatment, the immune system cleans up the pigment debris, virtually restoring the pre-tattooed skin condition. One persistent question regarding this procedure is: how safe is the debris?

The answer to this question relies on the identification of the pigment debris after the treatment. Well-developed techniques of analytical chemistry, such as gas chromatography with mass spectrometry (GC-MS), are perfectly suited for such analysis, as was recently demonstrated by a team of German scientists. In August 2015, a paper appeared in Scientific Reports, an online, open access journal from Nature Publishing Group. The paper reported that, under laser illumination, disintegration of phtalocyanine blue (commonly used dye in blue tattoo ink) would produce hydrogen cyanide, a compound with high cellular toxicity. Aside from the potential public health policy implications, this finding is significant, because chemicals resulting from laser treatment affect the subsequent skin recovery process, which is, according to a recent review on the precautions of laser tattoo removal, not yet fully understood. Looking forward, studies like the one cited above will stimulate the development of smarter and safer tattoo pigments, a niche of exciting science on its own.