We used light to irradiate skin-derived stem cells and tried to find any cellular protein alterations 24 h after illumination. A 266-nm laser with four intensities was used, and of the nine cell markers that were surveyed in our trials, only CD90 was downregulated at an intensity of 20 μJ for 10 s. Repeated illuminations from the 266-nm laser at seven intensities revealed that CD90 expression was downregulated 14.6-28.8%, depending on light intensity. The maximal effect was noted at an intensity of 30 μJ for 2 s. This innovative finding reveals that a 266-nm laser can regulate protein expression in skin-derivative stem cells.