Paradoxical darkening of unperceived tattoo ink after relatively low fluence from a Q-switched Nd:YAG (1064-nm) laser in the course of treatment for melasma

Summary Although Q-switched (QS) lasers are the mainstay of modern tattoo removal, paradoxical darkening of tattoo ink may occur. This darkening of tattoo ink is dependent on laser wavelength, pulse duration and fluence, with high-energy, nanosecond-pulsed lasers more prone to induce tattoo-ink darkening. Laser toning, consisting of multiple-passed QS neodymium:yttrium–aluminum–garnet (Nd:YAG), 1064-nm laser treatment with low fluence, short pulse duration (< 10 ns), and a repetition rate of 10 Hz has been successful in the treatment of melasma. A mistake commonly made during laser toning is to scorch scalp hair, eyebrows or eyelashes, but this phenomenon is reversible. A more problematic error is caused by treatment of eyeliner or eyebrow tattoos. We report a patient who experienced changes in unperceived, skin-coloured tattoos, turning them blue after QS Nd:YAG laser treatment of melasma.