According to research from the Milken Institute School of Public Health, certain areas of the skin, such as behind the ears and between the toes, can be breeding grounds for harmful bacteria.
Study leader Marcos Pérez-Losada and study co-author Kate Crandall found that areas behind the ears, inside the abdomen and between the toes had less microbial diversity than areas such as the hands or lower legs. Crandall says that the diversity of microbes in the skin's microbiome can lead to a healthy microbial population, reducing the risk of skin conditions like acne and eczema.
According to the Centers for Disease Control and Prevention, germs or microbes are found in all living organisms and are organized into groups called microbiomes.
"If you have an unhealthy microbiome, it's because everything is dominated by one or two particular species," said Crandall, a professor of biostatistics and bioinformatics. "When you're reducing diversity, it's an unhealthy environment."
When Perez-Losada, a professor of biostatistics and bioinformatics at Crandall, told him about the topics of his students' semester-long genome research project, he told them to look at a piece of skin that his grandfather had ordered him to wash. . Crandall Pérez-Losada and his students confirmed what Crandall called the "grandfather hypothesis," which suggests that there are differences in the skin's microbiome, particularly between oily, moist, and dry areas.
"Most people thought the skin microbiome was uniform," Crandall said. "Once you wash the skin everywhere, you get the microbiome of the skin, and as with most of these microbiology studies, if you look a little closer, you'll find other changes that we didn't expect in the treatment."
An unhealthy microbiome is usually dominated by one or two bacteria, Crandall says. In contrast, a healthy microbiome consists of more than 1,000 different types of microbes that people can find when they wash their skin to kill overactive bacteria, he said.
“Grandpa was right,” Crandall said. "Take her advice and be sure to wash behind your ears, between your toes, and around your stomach."
Genomics students were allowed to wash body parts to collect data for the study, using arms and legs as controls. According to the study, 579 samples from 129 "healthy" adults were tested. The students also prepared DNA mixes for PCR before sending them to the Milken GW Genomics Core sequencing lab, Crandall said.
“You learn about PCR, you learn about DNA sequencing and you learn the application of all these concepts along the way,” Crandall said. "You get consistent data, and then you start doing analysis and learning about analysis, and then you go into statistical hypothesis testing and big hypothesis testing."
Pérez-Losada and Crandall described the educational experiment in a study published in 2020. Pérez-Losada repeated this educational experiment over four years and published the cumulative data of the new study confirming the diversity of the skin microbiome.
"Like any good study, we will publish it and show it to other researchers, especially if it focuses on the skin," Crandall said.
Perez-Losada and Crandall plan to collaborate with Nationwide Children's Hospital and continue working with colleagues at Milken to study other aspects of the microbiome, such as the effects of artificial sweeteners on the gut microbiome in cystic fibrosis. Crandall said he hopes the study will contribute to further microbiome research.
"This clearly has implications for dermatology and skin health, probably because of the risk of serious acne," Crandall said. “The military works a lot on the wound microbiome, wound healing and infections. Much of this data can be useful in understanding the skin microbiome and the fact that different areas of the skin have different levels of diversity and different components of the microbiome.
Experts who specialize in the study of the skin microbiome say that despite the health benefits of various microbes, people believe that bacteria on the skin is a sign of impurities.
Eli Acosta, a doctoral student at Yale University, said the study's findings about the lack of diversity of bacteria on the skin in humans are interesting compared to the diversity of the human gut microbiome. Various.
"There's a lot of variation [in the gut microbiome] between people living in different geographic regions and people with different life experiences, but the skin microbiome seems to be very similar and uniform across people," Acosta said.
The next steps in skin microbiome research could determine why different areas of the skin harbor different bacteria, Acosta said. He said the research could help identify the bacteria that cause skin conditions such as acne and eczema and help develop treatments to target those conditions.
Acosta adds that despite the common belief that bacteria on the skin are harmful, most of the bacteria are beneficial and critical to the development of the immune response. The overgrowth of certain bacteria can cause skin conditions such as dermatitis, he said.
"There's a misconception about the skin microbiome that we're all covered in bacteria all the time and it's hard and we need to try to get rid of that, because that's not true," Acosta said.
According to Travis Blackock, assistant professor of dermatology at Emory University, society in general underestimates the cleanliness of the skin, and dirt is equal to the number of bacteria on the skin. According to him, these stereotypes send the wrong signals that encourage people to try to get rid of germs on their skin in order to stay clean and healthy.
Blalock said the grandmother hypothesis adds emotional value to the research, but it also downplays the complexity of the skin microbiome because it focuses on keeping the skin clean and maintaining a healthy skin microbiome. The research could help dermatologists educate their patients and tailor skin care products to specific skin areas, he said.
"[The study] challenges the dogma that associates the absence of bacteria with cleanliness and health, suggesting that a balanced bacterial skin microbiome in all areas of the skin contributes to overall health," Black said in an email. .