Behind the term "LED mask" lies a mechanism documented since the 1990s: photobiomodulation. Cytochrome c oxidase, the last enzyme in the mitochondrial respiratory chain, absorbs red and near-infrared light. This absorption boosts ATP production, which in turn fuels fibroblast activity.
It's an indirect, gradual effect, which is why results take weeks rather than days. The literature remains uneven: variable protocols, often small samples, few independent trials on home-use devices.
Red (630-660 nm), near-infrared (850 nm) and blue (415 nm) rest on solid literature. Yellow (590 nm) is more weakly documented for home use.
Sources
Avci P. et al., "Low-level laser (light) therapy (LLLT) in skin," Seminars in Cutaneous Medicine and Surgery, 2013. Wunsch A., Matuschka K., Photomedicine and Laser Surgery, 2014.