It is already known that a tan color "healthy glow" indicates the damage of skin cells.
But a new study of vacationers found that sun exposure can also alter the skin's microbiome, altering the population of skin-dwelling bacteria in ways that can be harmful to health.
Lead researcher Abigail Langton says the microbiome recovers within a month, but during that time a person will be more susceptible to skin problems. He is a professor at the Dermatology Research Center at the University of Manchester, England.
"During the 28-day recovery period after vacation, the skin is less healthy and susceptible to infection or irritation due to proteobacteria (a type of bacteria that live on the skin) and general changes in skin balance." Dr. Langton.
In this study, researchers examined the skin of 21 healthy volunteers before a scheduled vacation in a sunny location. The team analyzed the composition of the microbiota found on the skin, specifically the three main bacterial communities found there.
The research team then tested the participants' skin on the day they returned and 28 and 84 days after their vacation.
The researchers categorized the vacationers based on their sun exposure: eight "tan seekers" outdoors, seven "tanned" before and six "avoided" after their skin tone. holiday
All sun worshipers had significant changes in microbial diversity after the trip.
"In our study, only those who avoided tanning (avoided sunlight) maintained a diversity of skin microbiomes after vacation," Langton said.
However, those who tanned on vacation had markedly reduced proteobacteria. Researchers say fluctuations in Proteobacteria are linked to eczema and psoriasis.
"It was unexpected that sun exposure would affect the skin microbiota so drastically," Langton said. "In our future research, we want to understand why members of the Proteobacteria group are particularly sensitive to UV light and how this change in diversity affects the long-term health of human skin."
The findings make sense because UV light is often used to sterilize surfaces such as lab benches and keyboards, Dr. Dr. Adam Friedman, chief of dermatology at the George Washington College of Medicine and Health Sciences in Washington, DC.
"We know that UVB light is antimicrobial. Unblocked UVB light can kill the microorganisms that infect our skin, including some 500 or more species," Friedman said.
"We're walking on big petri dishes," he continued. "UVB-induced skin damage changes the Petri dish, and those changes happen very quickly."
Friedman said UV rays alone suppress the skin's immune system and can cause skin cancer.
These UV-induced changes in the skin microbiome can lead to infections after exposure to sunlight reduces their defenses.
"We know that the organisms that live on our skin play a role in regulating the immune response, protecting us from the environment," Friedman said. "When diversity is reduced, this change can be a trigger for inflammation. During infection, it can lead to an inappropriate immune response."
He also said that changes in bacteria can increase the risk of skin cancer.
"Could this disruption of microbial diversity play a role in carcinogenesis? Maybe. I wouldn't be surprised," Friedman said.
But he points out that there are many other factors related to sun exposure—salty seawater, sunscreen, even sun-hardened skin—that also affect the skin's microbiome.
Friedman concluded that what needs to be done to protect the microbiome is not clear from this research.
"It doesn't tell us exactly what to do and what to avoid," Friedman said. "But I think it will open the door to further exploration."
Friedman said future research could determine whether courses of prebiotics or other microbiome protectors may be as essential to skin health as sunscreen.
Meanwhile, Langton and Friedman recommend that everyone protect themselves from the sun when outdoors.
"It's important for everyone to practice sun protection, including using a broad-spectrum sunscreen and seeking shade where possible, but especially between 11 a.m. and 3 p.m., when the sun is strongest," said Langton.
The new study was published Tuesday in the journal Frontiers in Aging.
More information
The US Food and Drug Administration has more on the dangers of tanning.
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