Researchers have shown that excessive sun exposure can adversely affect the short-term diversity and composition of skin bacterial composition. The skin is the largest organ of the human body and is home to a variety of bacteria, fungi, and viruses that together make up the skin microbiota. Among other roles, these microbial populations, organized in complex community structures, protect against pathogens.
Even though prolonged exposure to UV rays can cause DNA damage to skin cells, inflammation and early signs of skin aging, many people still consciously go out in the sun.
Due to a lack of research into how individual behavior affects UV-related microbiota changes and how this may relate to skin health, researchers in the UK have now examined the impact of sun-seeking behavior on the composition of holidaymakers' skin microbiota.
Dr Abigail Langton, lead researcher at the University of Manchester and corresponding author of the study published in the journal Frontiers in Aging, said: "We found in a group of holidaymakers that their sun exposure behavior significantly affected the diversity and composition of their skin microbiota. It was shown that skin tanning was associated with reduced abundance of proteinaceous bacteria in the post-holiday period. However, the microbiomes of all holidaymakers recovered a few weeks after they stopped spending time in the sun."
Sun exposure damages skin bacteria
Researchers analyzed the participants' skin before taking a vacation to a sun-drenched destination that lasted at least seven days. The skin microbiota consists mainly of three bacterial communities on the surface: Actinomycetes, Proteobacteria, and Firmicutes. Participants' skin microbiota was assessed again on days 1, 28, and 84 after vacation.
In addition, each vacationer was assigned a group based on his or her tanning reaction. Eight of the 21 participants had tanned while on vacation and were considered "seekers." The "tanning" group consisted of seven people who were already tanned on departure and maintained their tan throughout their holiday. These two groups were classified as "sun seekers". The remaining six participants were considered "tanning avoiders"; their skin tone was the same before and after the holiday.
Dr Thomas Willmott, lead author of the study and a researcher at the University of Manchester, explained: "This study was conducted on real-life holidaymakers and provides us with important insights into how tanning reactions caused by sun exposure - even during relatively short periods of daylight - can lead to a dramatic decrease in the abundance of Proteobacteria and thus reduce the diversity of the skin microbiota."
Despite the rapid decrease in Proteobacteria and concomitant changes in the diversity of the skin microbiota, the bacterial community structure had recovered 28 days after people returned from vacation. This suggests that exposure to UV rays while on vacation can have an acute impact on the skin microbiome, but that recovery is relatively rapid once back in a less sunny climate.
Disturbed microbiota can lead to health problems
Proteobacteria dominate the skin microbiota. It is therefore not surprising that the microbiota quickly recovers to re-establish the optimal functional conditions of the skin. Perhaps even more concerning, the authors note, are rapid changes in microbiota diversity, which are associated with disease states. For example, reduced bacterial abundance in the skin has previously been associated with dermatitis. In particular, fluctuations in Proteobacteria diversity have been linked to skin problems such as eczema and psoriasis.
The researchers note that future studies should explore why Proteobacteria appear to be particularly sensitive to UV rays and how changes in this diversity may affect skin health over the long term. Ideally, the goal of such studies is to increase the number of participants to gain further insight into the situation.