light energy out of the skin. The gold standard of tattoo removal treatment modality is considered to be laser tattoo removal using multiple separate Q-switched lasers (depending on the specific wavelengths needed for the dyes involved) over a number of repeat visits. There are several types of Q-switched lasers, and each is effective at removing a different range of the color spectrum. Lasers developed during or after 2006 provide multiple wavelengths and can successfully treat a much broader range of tattoo pigments than previous individual Q-switched lasers. Unfortunately the dye systems used to change the wavelength result in significant power reduction such that the use of multiple separate specific wavelength lasers remains the gold standard. The energy density (fluence), expressed as joules/cm2, is determined prior to each treatment as well as the spot size and repetition rate (hertz). To mitigate pain the preferred method is simply to cool the area before and during treatment with a medical-grade chiller/cooler and to use a topical anesthetic. During the treatment process, the laser beam passes through the skin, targeting the ink resting in a liquid state within. While it is possible to see immediate results, in most cases the fading occurs gradually over the 7–8 week healing period between treatments. Q-switched lasers are reported by the National Institutes of Health to result in scarring only rarely. Areas with thin skin will be more likely to scar than thicker-skinned areas. By 2023, the laser tattoo removal market is expected to grow 12.7% annually. Mechanism of laser action Experimental observations of the effects of short-pulsed lasers on tattoos were first reported in the late 1960s by Leon Goldman and others. In 1979 an argon laser was used for tattoo removal in 28 patients, with limited success. In 1978 a carbon dioxide laser was also used, but because it targeted water, a chromophore present in all cells, this type of laser generally caused scarring after treatments. In the early 1980s, a new clinical study began in Canniesburn Hospital's Burns and Plastic Surgery Unit, in Glasgow, Scotland, into the effects of Q-switched ruby laser energy on blue/black tattoos. Further studies into other tattoo colors were then carried out with various degrees of success. Research at the University of Strathclyde, Glasgow also showed that there was no detectable mutagenicity in tissues following irradiation with the Q-switched ruby laser. This essentially shows that the treatment is safe, from a