Too much exposure to the sun affects the short-term diversity and composition of the skin’s bacterial makeup, according to a study published in Frontiers in Aging.
The skin is the largest organ in the human body. It’s home to multiple types of bacteria, fungi, and viruses, forming the skin microbiota. Among other functions, these microorganisms protect against pathogens. However, we don’t understand how exposure to the sun affects these organisms.
To understand how exposure to the sun affects skin microbiota, a team of UK researchers from the University of Manchester examined the effects of sun-seeking behaviors on the skin microbiota composition of holidaymakers.
“Here we show in a cohort of holidaymakers that their sun exposure behavior significantly affects the diversity and composition of their skin microbiota,” said Dr Abigail Langton. “We have demonstrated that the development of a tan is associated with lower Proteobacteria abundance immediately post-holiday. However, the microbiota of all holidaymakers was recovered a few weeks after they stopped spending extended time periods in the sun.”
The team analysed the skin of participants in the study before they went on a 7-day holiday. At this stage, the skin microbiota comprised three bacterial types: Actinobacteria, Proteobacteria, and Firmicutes. The same exam was repeated on days 28 and 84 after the holidays. Those who had a tan after the holidays were classed as “sun seekers,” while those whose skin tone didn’t change were tagged as “sun avoiders.”
The results showed a rapid drop in Proteobacteria in the “sun seekers,” but the bacterial community had recovered to normal levels 28 days after the holiday. “This study was performed in real-life holidaymakers and provides important insights into how sun exposure resulting in a tanning response – even over a relatively short sunny period – can lead to an acute reduction in Proteobacteria abundance, which decreased skin microbiota diversity,” said Dr. Thomas Willmott, the study’s first author. “This indicates that UV exposure on holiday has an acute effect on the skin microbiota, but recovery is relatively rapid once the person returns to a less sunny climate.”
Despite the rapid recovery, the authors warn that the fact that skin microbiota can change so quickly may be of concern. Similar changes have been linked to skin diseases: Dermatitis is associated with a decrease in bacterial diversity, and eczema and psoriasis involve a reduction in Proteobacteria diversity.
The authors suggest that future studies must examine why Proteobacteria seem particularly sensitive to UVR and how this change impacts long-term skin health. “Ideally, such studies will aim to increase the number of participants to allow further insights,” concluded Langton.
Willmott T, Campbell P, et al (2023) Behaviour and sun exposure in holidaymakers alters skin microbiota composition and diversity. Front. Aging, https://doi.org/10.3389/fragi.2023.1217635