Some Aspects of the Skin Microbiome Remain Elusive

SAN DIEGO — Although it has been known for several years that more than 1000 species of bacteria from 19 different phyla inhabit the human skin — mainly the superficial epidermis and upper parts of the hair follicles — published studies specifically focusing on the skin microbiome remain limited. 

In one review of the topic, researchers from the National Institutes of Health wrote that the skin is composed of 1.8 million diverse habitats with an abundance of folds, invaginations, and specialized niches that support a wide range of microorganisms. “Many of these microorganisms are harmless and, in some cases, provide vital functions for us to live and they have not evolved over time,” Jill S. Waibel, MD, medical director of the Miami Dermatology and Laser Institute, said at the annual Masters of Aesthetics Symposium. 

“This is complex ecosystem that we don’t really talk about,” she said. “There is wide topographical distribution of bacteria on skin sites. The bacteria we have on our head and neck area is different from that on our feet. There is also a lot of interpersonal variation of the skin microbiome, so one person may have a lot of one type of bacteria and not as much of another.” 

A Shield From Foreign Pathogens

At its core, Waibel continued, the skin microbiome functions as an interface between the human body and the environment, a physical barrier that prevents the invasion of foreign pathogens. The skin also provides a home to commensal microbiota. She likened the skin’s landscape to that of the tundra: “It’s desiccated, has poor nutrients, and it’s very acidic, thus pathogens have a hard time living on it,” she said. “However, our skin microorganisms have adapted to utilize the sparse nutrients available on the skin. That’s why I tell my patients, ‘ on’t use a sugar scrub because you’re potentially feeding these bad bacteria.'” 

According to more recent research, the skin microbiota in healthy adults remains stable over time, despite environmental perturbations, and they have important roles in educating the innate and adaptive arms of the cutaneous immune system.”Some skin diseases are associated with an altered microbial state: dysbiosis,” said Waibel, who is also subsection chief of dermatology at Baptist Health South Florida, Miami Beach. “Reversion of this may help prevent or treat the disease.” 

She cited the following factors that influence the skin microbiome: 

• Genetics affect s the skin microbiome considerably. Individuals with autoimmune predispositions have different microbiota compared with those who don’t.
• Climate, pollution, and hygiene practices the other influencing factors. “Even clothing can impact the microbiome, by causing the transfer of microorganisms,” she said.
• Age and hormonal changes (particularly during puberty) and senescence alter the microbial landscape.
• Systemic health conditions such as diabetes mellitus and irritable bowel disease, as well as cutaneous conditions like psoriasis and atopic dermatitis can also disrupt the skin microbiome.

Ingredients contained in soaps, antibiotics, and cosmetics can also cause skin dysbiosis, Waibel said. However, the integrity of the skin’s microbiome following dermatological procedures such as excisions, dermabrasion, laser therapy, and other physical procedures is less understood, according to a recent review of the topic. Phototherapy appears to be the most extensively studied, “and shows an increase in microbial diversity post-treatment,” Waibel said. “Light treatments have been found to kill bacteria by inducing DNA damage. More studies need to be performed on specific wavelengths of light used, conditions being treated and individual patient differences.” 

According to the review’s authors, no change in the microbiome was observed in studies of debridement. “That was surprising, as it is a method to remove unhealthy tissue that often contains pathogenic bacteria,” Waibel said. “The big take-home message is that we need more research.” 

Waibel disclosed that she has conducted clinical trials for several device and pharmaceutical companies.