Changes in the cutaneous microbiome triggered by warmer temperatures and increased UV radiation may stimulate C. acnes growth.
Cumulative data in recent years suggest that fossil fuel combustion results in not only significant environmental impacts but also considerable impacts on both overall and cutaneous health.1 While its negative impact on environment health is clear, the effects that fossil fuel combustion and a warming world have on skin disease, including acne have only more recently been explored.1
Markus D. Boos, MD, PhD, and colleagues, who published a recent paper in the International Journal of Dermatology, noted that there is “clear evidence” that changes in certain climatic variables—such as air pollution, humidity, temperature, and ultraviolet (UV) radiation—affect not only distinct cutaneous disorders, but also have direct effects on the skin microbiome.1 Moreover, these climate factors appear to “influence the severity of one another” and have differential effects on the cutaneous microbiome, thereby creating complexities in how they can be potentially addressed, Boos told Dermatology Times®.
Boos, an attending pediatric dermatologist at Seattle Children’s Hospital and an associate professor in the department of pediatrics at the University of Washington School of Medicine, also in Seattle, along with a small research team, reviewed the available literature that discussed the effects of changes in climatic variables on the skin microbiome.
Based on this review, Boos noted that there are several established links between skin health and the combustion of fossil fuels and climate change. “But the question with this [research] project was to dig a bit deeper and ask if there is an intermediary link between climatic variables and skin disease that we're not considering,” he explained. “Something might be a risk factor for what we're seeing manifest in the skin, but what we want to know is if what we're seeing could be mediated by changes in the cutaneous microbiome.”
Climatic Variables and the Cutaneous Microbiome: What’s the Connection?
Stratospheric ozone depletion—due to the use of chlorofluorocarbons and other compounds—has led to increased levels of UV radiation over recent decades, Boos and colleagues explained in their paper. The chemicals, which function as potent greenhouse gases, increase effective surface levels of UV radiation and consequently hold critical implications for skin health.
Boos and researchers explained that several skin bacteria produce antioxidants that prevent UV-induced carcinogenesis. Specifically, the investigators cite data from a murine model which show that a certain Staphylococcus epidermidis strain may suppress UV-induced tumor growth. While potentially protective, Boos and colleagues noted that cutaneous bacteria may be more vulnerable to higher effective UV radiation doses at increased temperatures, which are direct consequences of the changing climate.
For acne, changes in temperature and increased UV radiation are correlated with disease flares. Specifically, the researchers cite evidence that warmer temperatures increase sebum levels, humidity increases pilosebaceous unit swelling, and UV radiation results in hyperplasia of sebaceous glands, consequently promoting growth of Cutibacterium acnes.1 Although these changes may depend on an individual patient’s microbiome, they could increase C. acnes and lead to persistent inflammation and the precipitation of acne flares “in the absence of other competing microbes,” the researchers explained.
Addressing Gaps in Knowledge
Despite the important association between climate change and skin health, there are still critical knowledge gaps regarding this association and its relation to driving or exacerbating skin diseases. “If increased UV radiation puts you at risk for skin cancer, but it also has effects on other things such as inflammatory diseases like atopic dermatitis or psoriasis, then we need to think about if there is another component to that association,” Boos explained.
Part of the problem with developing solutions to climate change and its effects on skin health is the multivariable nature of the issue, Boos explained. “And all of those variables affect one another,” he stated.
For example, Boos added that with every 1-degree centigrade increase in temperature, the effective UV dose increases by 2%. “So even something as simple as UV radiation varies depending on what the temperature is and how that consequently affects your skin,” he said.
According to the researchers, the use of 3-dimensional (3D) human skin models in vitro could be useful in studying the skin microbiome in relation to the changing climate. With 3D skin models, Boos explained that researchers can control all climate-related variables, including humidity, temperature, and what bacterial species are on the skin at any given time.
Further Research Directions
One of the big-picture questions, according to Boos, is whether bacteria are really mediating climatic variables and how these variables actually affect the skin. “That's an important question, because for different conditions, like acne, people are talking about the applicability of skin bacteria transplants as a therapeutic option,” he added.
But short of ceasing the burning of fossil fuels and eliminating pollution altogether, which isn’t an easy feat in today’s world, Boos suggested that there is interest in leveraging the bacteria on the skin to mitigate the changing environment’s effects on dermatologic outcomes.
Further research is also necessary to better understand how the environment modifies the human microbiome, as this improved understanding “holds promise for the treatment and prevention of skin disease,” Boos and colleagues wrote in their paper.
The study researchers reported no conflicts of interest with the pharmaceutical industry.
1. Isler MF, Coates SJ, Boos MD. Climate change, the cutaneous microbiome and skin disease: implications for a warming world [published online ahead of print, 2022 May 22]. Int J Dermatol. 2022;10.1111/ijd.16297. doi:10.1111/ijd.16297