Skin–immune cross-talk

The skin, the body’s largest organ, serves as a dynamic interface between the external environment and internal homeostasis. In addition to its roles in barrier protection and sensory perception, it functions as an active immune organ, working in coordination with systemic immune networks¹. This interaction, termed skin–immune system cross-talk, has significant implications for infant health, immune development, and the pathogenesis of dermatological and systemic conditions.

Role of the Skin Microbiome in Health and Disease

• The skin microbiome interacts closely with host cells and is influenced by immune responses and external factors such as antibiotic exposure.
• It promotes early immunological tolerance, produces antimicrobial peptides and regulatory metabolites, and supports wound healing and barrier integrity.
• The microbiome also regulates keratinocyte activity and immune signaling, while pathogenic organisms and pathobionts can disrupt these processes and contribute to disease².

Mechanisms of Skin–Immune System Cross-Talk

• The skin microbiome evolves with age, influenced by host physiology, environmental exposures, and site-specific characteristics.
• Neonatal skin exhibits distinct immune activity and undergoes rapid colonization after birth by maternal and environmental microbes, shaping long-term immune tolerance.
• Early microbial exposure, such as colonization with Staphylococcus epidermidis, promotes regulatory T-cell development and anti-inflammatory responses.
• Microbiome stabilization typically occurs around 3 years of age, with additional changes during puberty and aging due to hormonal and metabolic shifts.
• Skin commensals interact with keratinocytes and immune cells to maintain barrier integrity, regulate antimicrobial peptides, and modulate inflammation.
• Staphylococcus epidermidis supports barrier and immune function, whereas pathogens such as Staphylococcus aureus can disrupt these processes.
• Specialized immune cells, including Langerhans cells, dendritic cells, mast cells, and mucosal-associated invariant T (MAIT) cells, coordinate host–microbe interactions to promote tolerance and epithelial homeostasis³.

Clinical Implications

• Early-life dysbiosis or reduced exposure to beneficial environmental microbes can disrupt host–microbe interactions, increasing the risk of inflammatory skin conditions such as atopic dermatitis.
• Atopic dermatitis affects up to 20% of children and often represents the first stage of the “atopic march,” preceding conditions such as food allergies, asthma, and allergic rhinitis⁴.
• Emerging evidence suggests that early interventions aimed at restoring skin barrier function and supporting microbiome balance may help prevent disease progression.

Conclusion

Skin–immune system cross-talk in early life plays a fundamental role in shaping immune tolerance, barrier integrity, and long-term skin health. Understanding these interactions provides a foundation for preventive and therapeutic strategies in pediatric dermatology.

References

1. Yamamura K, Shiraishi A, Sato E, et al. Crosstalk between skin and immune cells. Front Immunol. 2025;16:1739229.
2. Liu Q, Ranallo R, Rios C, et al. Skin microbiota and immune system interactions. Nat Immunol. 2023;24(6):895–898.
3. Lunjani N, Ahearn-Ford S, Dube FS, et al. Microbe–immune system dialogue in skin. Genes Immun. 2021;22(5–6):276–288.
4. Maintz L, Bieber T, Simpson HD, et al. Skin barrier dysfunction and systemic impact of atopic dermatitis. J Pers Med. 2022;12(6):893.