Secondary Effects

When skin is exposed to infrared light, there is the distinct possibility that some of the energy will result in secondary molecular/biochemical events. In experimental studies, various biological systems, that is, cell-based studies have reported changes in matrix met­alloproteinase (MMP) expression [131,132], perhaps as a result of free radical formation [133] and other events [134], most of which have been discussed in the context of photoag­ing of the skin. Where the potential for lasers to produce free radicals exists, at lower doses, such events are unlikely. This view is supported by at least one study which found no effect of ruby laser on free radical formation in human-skin biopsies [135]. Moreover, there is some evidence that IR exposure will increase antioxidant activity in skin [136]. Regardless of this fact, at the doses and frequency of treatments used in dermatological practice, the contribution of oxidative stress/damage following exposure to currently available lasers would seem to be minor.