Session on the Skin Microbiome and Atopic Dermatitis Presented at 2025 SDPA Fall Conference

The Society of Dermatology Physician Associates (SDPA) Fall Conference in San Antonio, Texas, a session was presented by Rosemary Son, MPAS, PA-C, RDN, who spoke in this talk about current information and updates on the cutaneous microbiome, drawing mainly on recent publications published within the Journal of the American Academy of Dermatology (JAAD).1

In this session, Son highlighted the rapidly-changing nature of research in this space and noted the available evidence remains largely associative rather than causal. In her talk, Son provided an overview of microbiome composition, links with dermatologic conditions, determinants of microbial variation, and recent insights related to host–microbe interactions.2

"[The microbiome] encompasses all of the organisms that live in and on us, and that includes your bacteria, fungi, mites, viruses that inhabit both the outer surface and some of your inner surfaces," Son explained.1 "...Every nook or cranny that you have has things living in it. And how we define the skin microbiome is the community of all of the genes of all of those things. I think the broad way that micro the microbiome is whether or not [the microbes on us] are friendly, neutral, or actively not nice to us."

One of the activities done by the body's commensal organisms is the production compounds that defend themselves and protect the human body from such invaders as bacterial toxins from staph infections. They also help stimulate certain immune responses, Son noted.

Son went on to describe humans as “planets” with distinct ecological niches; oily, dry, and moist areas of the body are included in her list. These areas support characteristic microbial communities, she added. Sebaceous areas are known to be enriched with Cutibacterium acnes, moist regions host higher proportions of Staphylococcus as well as Corynebacterium, and the feet exhibit greater fungal diversity relative to other bodily regions.

"There's still a lot we don't know, and that's why it's so interesting and titillating," Son said.1 "We're just kind of beginning to scratch the surface of what this actually means. The interesting thing is that there's a lot of variability on body sites, both between an individual, but even on their own body areas."

Intrinsic and extrinsic factors are believed to shape these microbial populations, Son highlighted. She noted extrinsic influences include environmental exposures, such as swimming, fabric type, and even pandemic-related mask use. She went on to discuss antibiotics' role in inducing lasting shifts in the body's skin microbiome. Prolonged dermatologic antibiotic therapy is, consequently, a concern.

Intrinsic influences covered by Son in her presentation include puberty-linked hormonal shifts, mode of birth, sex distinctions in the creation of sebum, and age-related shifts in one's level of fungal diversity. Son noted research indicating microbial signatures may predict human age within several years. She also commented on the markedly similar microbial profiles of twins.

"It turns out that twins not only have a lot of their genes in common, like their clones, but their microbiomes are very more closely related [compared to] unrelated folks," she explained.1 "Certainly, the way that you were made has an influence on what kind of creatures want to live there."

The pilosebaceous unit was described by Son as a central hub for microbe–host interactions. This lipid-rich, low-oxygen microenvironment is supportive to C acnes and numerous other organisms, Son said, and it serves as the origin for several dermatologic conditions. Microbial changes, such as C acnes ribotype switching, were described by Son as converting commensal organisms into pathogenic ones, contributing to acne and other follicular issues on patients' skin.

Throughout her talk, Son reviewed the multifaceted role of the microbiome in maintaining cutaneous barrier integrity. The highlighted commensal organisms, describing them metaphorically as protective “guard dogs." This is due to their production of antimicrobial peptides known to inhibit certain pathogens. Additionally, disease-specific information was addressed with emphasis on atopic dermatitis, a skin disease consistently linked to diminished microbial diversity and overrepresentation of specific S aureus strains. Son implemented an analogy contrasting the healthy microbiome to a diverse national park and the atopic dermatitis microbiome was described as an overrun monoculture lacking ecological balance.

Son's talk concluded with acknowledgment of major knowledge gaps and the need for longitudinal human research, standardized methods, and translational work to develop microbiome-based treatments for patients. While topical emollients and barrier-supportive care continue to be foundational, impacrting patients' microbial health, targeted microbiome interventions were described as not yet widely available or reliably effective.

References

1. Son R. We Contain Multitudes: The microbiome and skin disease. Presented at the Society of Dermatology Physician Associates (SDPA) Fall Conference, November 5-9, 2025, San Antonio, TX.

2. Whiting C, Abdel Azim S, Friedman A. The Skin Microbiome and its Significance for Dermatologists. Am J Clin Dermatol. 2024 Mar;25(2):169-177. doi: 10.1007/s40257-023-00842-z. Epub 2024 Jan 22. PMID: 38252188.