How immune health and the risk of chronic skin diseases affect you from the beginning of life to adulthood

From birth to youth and into adulthood, the bacteria and fungi on the surface of the skin that are invisible to the naked eye are by no means simple "parasites". They engage in intricate "dialogues" and are deeply involved in the training and fine-tuning of the human immune system. However, once this delicate balance is broken, chronic inflammation and various skin diseases may follow. Recently, a review article published by a Korean research team in the authoritative journal Experimental & Molecular Medicine deeply analyzed the effects of skin microbiota on immune development, barrier function, and disease susceptibility, opening up a new perspective for our understanding of skin health.

Skin: The invisible kingdom of microorganisms

Human skin is like a bustling "microbial city" inhabited by billions of bacteria, fungi, and viruses. These symbiotic microorganisms are not "standing idly by" but directly participate in the maintenance of skin barrier integrity, tissue repair, and immune regulation through mechanisms such as secreting various metabolites and cleverly activating immune receptors. For example:

Staphylococcus hominis: If colonized in early infancy, the risk of atopic dermatitis can be reduced by 40%, as if it were a "protective umbrella" for the baby's delicate skin.

Staphylococcus epidermidis: It can produce ceramide, which acts like "cement" to strengthen the "brick wall structure" of the skin barrier. At the same time, through precise interactions with dendritic cells (DC) and regulatory T cells (Treg), the body develops tolerance to commensal bacteria and avoids overreaction of the immune system.

Propionibacterium acnes: Produces propionic acid, which activates the PPARα signaling pathway in keratinocytes, further enhancing the skin barrier function and safeguarding skin health.

Malassezia: It can inhibit the formation of Staphylococcus aureus biofilm and maintain the dynamic balance of skin microorganisms, just like a "traffic policeman" to ensure the "traffic order" of the microbial world.

Imprints of early life: the immune system's "foundational moment"

The first exposure to the skin microbiome in infancy leaves an indelible mark on life. For example, exposure to riboflavin-producing bacteria such as Staphylococcus epidermidis promotes the development of mucosa-associated invariant T cells (MAIT) and Tregs, which play a crucial role in immune tolerance. Experiments in mice have shown that early exposure to Staphylococcus aureus may even prevent atopic dermatitis; while the misuse of antibiotics or damage to the skin barrier may exacerbate inflammatory responses in adulthood and increase the risk of diseases such as psoriasis.

The cost of imbalance: from dysbiosis to chronic inflammation

When the skin microbiome is out of balance (called "dysbiosis"), inflammatory diseases can erupt like a volcano. For example:

Atopic dermatitis: The reduction of filaggrin leads to overgrowth of Staphylococcus aureus, which stimulates Th2 cells through cytokines such as IL-33 and TSLP, causing severe itching and skin damage, making patients miserable.

Psoriasis: The IL-23-IL-17 axis drives pathogenesis, and mice lacking a microbiome have milder symptoms, while the presence of Staphylococcus aureus and Candida albicans exacerbates lesions and makes the disease worse.

Acne: Although C. acnes (Propionibacterium acnes) is not the only cause, its imbalance with Staphylococcus epidermidis and reduced microbial diversity are closely related to increased inflammation.

The "two-sided nature" of symbiotic bacteria: friend or foe?

In a healthy state, skin microbes can guide immune cells to produce tolerance and maintain the body's immune balance through metabolites (such as indole-3-aldehyde); however, when immunosuppression or barrier damage occurs, they may transform into opportunistic pathogens. For example, Staphylococcus epidermidis may transform from a "friendly neighbor" to a "dangerous invader" by producing lipases and proteases.

Epigenetics: How microbes rewrite genes

Skin microbes may affect immune development through epigenetic modifications (such as changes in chromatin structure). For example, short-chain fatty acids (such as butyrate) produced by certain bacteria can block histone deacetylases and inhibit pathogen growth. Whether these changes will shape immune memory remains a key direction for future research, revealing deeper mysteries between microbes and genes.

Future Outlook: Microbiome-Targeted Therapy

Understanding the bidirectional interaction between skin microbes and host systems provides new ideas for personalized treatment. For example:

Probiotic intervention: Can early use of probiotics prevent chronic skin diseases? This concept offers new hope for preventive treatment.

Microbial metabolite therapy: Can metabolites such as indole-3-aldehyde become the next generation of anti-inflammatory drugs? This provides a new direction for the development of new drugs.

Research background and journal information

The review was carefully completed by a Korean research team and is titled "The Dialogue between Skin Microbiota and Host: From Early Life to Adulthood" and published in the 2025 issue of Experimental and Molecular Medicine. The study emphasizes that the skin microbiota is not only a "trainer" of the immune system but also a "behind-the-scenes promoter" that regulates gene expression through epigenetic modification, providing a new theoretical framework for our understanding of skin health.

Journal Reference :

Cha, J., Kim, TG, & Ryu, JH (2025). The dialogue between skin microbiota and host: from early life to adulthood. Experimental & Molecular Medicine, DOI: 10.1038/s12276-025-01427-y.

The study of skin microbiota is like a key that opens the door to the intricate symbiotic relationship between microorganisms and hosts. In the future, by precisely regulating the microbiome, we may be able to develop more effective strategies for the management of chronic skin diseases, bringing new hope for skin health and allowing everyone to have healthy and beautiful skin.