Purpose: The demand for epilation of large body areas involves using large laser spots. The emitted light causes the desired effect in follicular melanin, but it may also produce collateral effects on pigmented melanocytic nevi. To shield melanocytic lesions, several materials were tested for their capabilities to prevent transmission of alexandrite and diode laser light.
Materials and methods: Delivered fluence of the diode laser (808 nm, 30 J/cm(2), 12 ms) and the alexandrite laser (755 nm, 30 J/cm(2), 40 ms) and transmission rates were measured for glass slides only and additional sunscreen, polyurethane (PU) foam, zinc paste, white kajal, and a wooden spatula. For each method, ten repeated measurements were conducted. An ex vivo human skin explant model was used for histological validation.
Results: Using zinc as an absorber reduced transmission to 8.77% (diode) and 7.99% (alexandrite laser). Respectively transmissions were measured as following: PU foam 19.25% versus 20.78%, sunscreen 19.85% versus 16.91%, white kajal 76.43% versus 71.03% and wooden spatula 8.05% versus 3.62%. Histologically, a single application of therapeutic fluences (755 nm) in uncovered congenital nevi leads to immediate formation of atypical nucleoli, a ballooning degeneration of melanocytes, and subepidermal clefting within the treated area. In the sites of the lesions that were covered by zinc paste, PU foam, sunscreen and wooden spatula, no immediate histological changes were visible.
Conclusion: Applying a sufficient amount of zinc paste (approximately 1 g/cm(2)) onto melanocytic lesions allows complete coverage during laser epilation.