“…1,3 Furthermore, few reports discuss the mechanism of action of these systems. [2][3][4] At present, the following 2 hypotheses exist as to how these devices work: (1) The light energy is absorbed by water, and perhaps by collagen, to cause a direct thermal effect on the dermal ground substance; and (2) The light energy is absorbed by hemoglobin and/or melanin, triggering the cutaneous vessels and/or adnexal structures to produce cellular mediators and growth factors that may stimulate a wound-healing response, which would also give rise to indirect heating of the dermis and cause a response similar to the first proposed mechanism.…”