Strategic selection of multi-parametric laser settings and clinical endpoints in dermatology: an engineering-to-clinical review.

Selective photothermolysis, which enables precise targeting of melanin, hemoglobin, and water, is the foundation for modern dermatologic laser therapy. This review bridges laser physics with clinical practice by organizing systems on the basis of spectral domain and indication: Q-switched and picosecond lasers for tattoos and lentigines; pulsed-dye and long-pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers for vascular lesions; alexandrite and diode lasers for hair removal; and fractional ablative (CO₂, erbium-doped yttrium aluminum garnet [Er:YAG]) and non-ablative platforms for scar revision and rejuvenation. Unlike conventional textbook reviews that merely list device specifications, we specifically define how to dynamically adjust comprehensive parameters not just wavelength, but also pulse duration, fluence, and spot size-in direct response to immediate clinical endpoints observed during treatment. We delineated the selection of parameters-wavelength, pulse duration, fluence, and spot size-in relation to the Fitzpatrick skin type, focusing on cooling, treatment endpoints, and recovery. Current evidence regarding efficacy, recurrence, and complications has been synthesized, and the device parameters have been linked to thermal relaxation and Arrhenius injury kinetics to inform safer evidence-based algorithms and multimodal treatment strategies.