Bidirectional chemical communication between host cells andcutaneous microbes also occurs in response to UV-R. In murinestudies, S. epidermidis has been shown to provide protectionagainst inflammation secondary to chronic UVB exposure viafermentation of glycerol into butyric acid. Application of S. epidermidiswith glycerol or application of butyric acid aloneinduces significant decreases in interleukin (IL)-6, (a proinflammatory cytokine) that is typically released in response toUVB radiation. In contrast, application of S. epidermidis aloneor glycerol alone demonstrated minimal anti-inflammatoryeffects.24 Conversely, changes in the host environment fromUV-R exposure can also influence microbial growth. UV-R hasbeen reported to cause hyperplasia of sebaceous glands andthickening of the stratum corneum, potentially altering the microbial landscape by selecting lipophilic organisms.20 How microorganisms are affected by UV-R is an important area of futureexploration to determine host–microbe relationships that can beinfluenced by UV-R and subsequently influence future therapiesand disease prevention.Air pollutantsClimate change, global warming, and air pollution are all intertwined as byproducts of the combustion of fossil fuels.25