Changes in melanocytic nevi after hair removal techniques with laser and intense pulsed light

Lasers and intense pulsed light (IPL) systems are some of the most demanded techniques used for unwanted hair removal. They act by selective photothermolysis, a mechanism by which photons target the hair follicle me­la­no­cyes while, at the same time, sparing the sur­roun­ding tissue. However, when applied directly onto a pigmented lesion, the energy from the laser can be ab­sorbed by nevocytes, with subsequent thermal injury of the lesion. Few studies in the literature have described the consequences of laser and IPL devices on melanocytic nevi. Our aim was to summarize the clinical, dermatoscopic and histopathologic modifications that occurred in nevi after these hair removal techniques. We selected four case series and three case reports, totalling 12 patients, of which seven had been previously treated with laser and five with IPL for hair removal. Clinical modifications of nevi consisted in hy­per­pig­men­ta­tion, crust formation, two-colour aspect and complete clearance of nevi. Dermatoscopically, a change in pigment distribution and colour, microcrusts, grey-blue structures and a milky red veil were described. Histo­pa­th­o­lo­gical changes were consistent with inflammation and benignity. Ultraviolet radiation is known to cause DNA damage and mutagenesis, while the effects of visi­ble light and infrared laser on tissues are primarily ther­mal. However, we cannot definitively exclude the po­ten­tial for malignancy after repeated thermal trauma of nevo­me­la­nocytes.