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Knowledge on IRR effects over the skin is yet poorly known. IR-A has been reported to flow into the epidermis and dermis, thus reaching the subcutaneous tissue, though not promoting significant temperature increase, whereas IR-B and IR-C are both considerably absorbed by epiderm, thus promoting increase in temperature (Figure 1).
We are therefore to state, categorically, that heat may be generated as a consequence of exposure to IRR. Heat, per se, is the main stimulus to increase metalloproteinases (MMPs) enzyme expression as well as reactive oxygen species (ROS), just as the production of skin inflammatory mediators, such as pro-inflammatory cytokines, angiogenic and transcription factors, serine-proteases and signaling paths end up degradating extracellular matrix and other photoaging signs.
Besides the IRR, studies have highlighted the biological consequences of the exposure to visible light. Considering that 6.8% of the solar energy reaching the earth’s surface is in the UV range (0.5% UV-B and 6.3% UV-A), 38.9% in the visible range and 54.3% in the IR range, an individual is exposed to significant quantities of infrared radiation and visible light daily.
However, commercial sunscreens are designed only to block wavelengths within the range of UVB and UVA and thus, the skin is not protected against the effects of visible light. Liebel et al demonstrated that visible light can significantly induce the production of reactive oxygen species, which promote the release of proinflammatory cytokines and expression of MMPs, the cumulative effects of visible light can result in skin damage, favoring tissue premature aging.
According to the aforementioned, and concerning the latest complementary theories about skin aging, it is evident that protection from aggressions arising from photoexposure, no longer attributed to UVR, is essential to maintaining healthy skin characteristics, as well as aesthetically feasible. Within this context, dermocosmetic action, especially the ones acting onto all aging-related aspects, is of vital importance.