Microbiome of the Skin and Gut in Atopic Dermatitis (AD): Understanding the Pathophysiology and Finding Novel Management Strategies

Abstract

Atopic dermatitis (AD) is a long-standing inflammatory skin disease that is highly prevalent worldwide. Multiple factors contribute to AD, with genetics as well as the environment affecting disease development. Although AD shows signs of skin barrier defect and immunological deviation, the mechanism underlying AD is not well understood, and AD treatment is often very difficult. There is substantial data that AD patients have a disturbed microbial composition and lack microbial diversity in their skin and gut compared to controls, which contributes to disease onset and atopic march. It is not clear whether microbial change in AD is an outcome of barrier defect or the cause of barrier dysfunction and inflammation. However, a cross-talk between commensals and the immune system is now noticed, and their alteration is believed to affect the maturation of innate and adaptive immunity during early life. The novel concept of modifying skin and gut microbiome by applying moisturizers that contain nonpathogenic biomass or probiotic supplementation during early years may be a preventive and therapeutic option in high risk groups, but currently lacks evidence. This review discusses the nature of the skin and gut flora in AD, possible mechanisms of skin–gut interaction, and the therapeutic implications of microbiome correction in AD.

A Calm, Dispassionate Look at Skin Microbiota in Atopic Dermatitis: An Integrative Literature Review

“…The severity of AD is usually associated with biofilms formed by S. aureus [25]. A biofilm is a bacterial assemblage attached to the surface and enclosed in an extracellular matrix.…”

The Skin Microbiota and Itch: Is There a Link?

“…It produces ceramidase, which breaks down ceramides, an essential component of the skin barrier [34]. S. aureus also produces α toxins that impede wound healing and bring epithelial barrier disintegration [35].…”

Psychoneuroimmunology and skin diseases

“…According to findings in the last decade, stress stimulates the release of glucocorticoids that stimulate Th2 responses while inhibiting Th1 cellular responses 26. . In addition, stress can cause a hyperacute response with accompanying activation of T lymphocytes and mast cells, impaired regulation of the HPA axis, expression and release of neurogenic inflammation mediators, and dysfunction of normal epidermal barrier function 27 . In addition to HPA axis disregulation, stress-induced neuroimune effects reslting in skin inflammation also involve additional peripheral effects, glucocorticoid function disregulation and glucocorticoid receptor dysfunction 2 .…”

“…Another important factor to consider is the microbiota and its effect on skin disease within the psychoneuroimmunological perspective 27,61 . The skin microbiota, and other microbiotas, such as the gut microbiota, play a key role in pathogenesis and progression of atopic dermatitis.…”

“…On the other hand, the gut microbiota can modulate immune, metabolic and neuroendocrine functions. Various interventions aimed at microbiota characteristics are being developed to treat atopic dermatitis based on current research and underrstanding of the effects of microbiota on the onset of the disease 27 .…”