The Gut-Skin Axis
The Gut-Skin Axis — What Your Microbiome Has to Do With Your Skin
One of the most rapidly developing areas in dermatology and aesthetic medicine involves an organ most practitioners never examine. Here is what the emerging science of the gut-skin axis actually says — and what it means clinically.
An unexpected connection
The idea that the health of the gastrointestinal tract influences the health of the skin is not new. Clinicians have observed associations between gut disorders and skin conditions for over a century — the link between bowel disease and pyoderma gangrenosum, between coeliac disease and dermatitis herpetiformis, gut dysbiosis and rosacea, are all part of the established clinical literature.
What is new, and what is developing rapidly, is the mechanistic understanding of how these connections work and the growing evidence that the gut microbiome influences not just specific skin diseases but skin health, skin ageing, and skin barrier function in a more general and clinically significant way.
What the gut microbiome is and why it matters
The gut microbiome is the complex community of bacteria, fungi, viruses, and archaea — approximately 38 trillion microorganisms — that colonise the gastrointestinal tract.
Far from being passive inhabitants, these organisms are metabolically active participants in a range of physiological processes that extend well beyond digestion. The gut microbiota metabolises dietary components, xenobiotics, and drugs, while producing short-chain fatty acids, vitamins including K, B12, biotin, folic acid, and thiamine, secondary bile acids, and antimicrobial peptides. These provide antimicrobial protection and stimulate the innate immune system and immunoglobulin A secretion.
The diversity and composition of this microbial community is highly individual, shaped by genetics, diet, environment, medication history, and the cumulative experience of a lifetime. When that composition shifts away from a healthy balance, a state known as dysbiosis, the downstream consequences are not confined to the gut.
How the gut communicates with the skin
The gut-skin axis operates through several but overlapping pathways, and understanding them helps to explain both the clinical observations and the therapeutic implications.
Systemic inflammation is the most significant pathway. The gut microbiome influences skin health the regulation of systemic immunity, inflammatory responses, and metabolic pathways.
When dysbiosis occurs, the integrity of the intestinal epithelial barrier is compromised, a condition colloquially but usefully described as increased intestinal . This allows bacterial products, including lipopolysaccharides from gram-negative bacteria, to enter the systemic circulation and trigger a chronic low-grade inflammatory response.
When dysbiosis occurs, it can lead to increased gut permeability, which allows molecules to seep into the bloodstream, leading to skin inflammation and accelerated ageing. This systemic inflammatory state — increasingly referred to as inflammaging in the context of ageing — has measurable consequences for skin collagen, elastin, and barrier function.
Short-chain fatty acids (SCFAs) are metabolites produced by gut bacteria through the fermentation of dietary fibre, principally butyrate, propionate, and acetate. They are among the most important mediators of the gut-skin . Through their promotion of tight junction protein expression and keratinocyte growth, SCFAs ensure epidermal barrier integrity. By impacting T cell development and cytokine production, SCFAs shape the immune system and facilitate the of immunological homeostasis. Butyrate in particular has demonstrated anti-inflammatory and barrier-supporting properties in both gut and skin tissue, and the reduction in SCFA-producing bacteria that characterises gut dysbiosis has been associated with impaired barrier function and increased skin inflammation.
The immune axis is the third major . 70% of the body’s immune cells are located in or around the gut. The gut microbiome continuously BBL Hero and Moxi by Sciton modulates this immune system — promoting T cell development, the balance between pro- and anti-inflammatory responses, and influencing the systemic immune tone that ultimately determines how the skin responds to challenges from UV radiation, pollution, and pathogenic organisms. A gut microbiome in produces an immune system that is chronically tilted inflammation and a skin that reflects it.
The conditions most clearly connected
The evidence for the gut-skin axis is in the of specific inflammatory skin conditions. Numerous dermatological disorders, such as rosacea, psoriasis, atopic dermatitis, and acne vulgaris, have been linked to dysbiosis in the gut microbiota.
Rosacea is perhaps the most compelling example in the aesthetic medicine context. The association between rosacea and small intestinal bacterial overgrowth (SIBO) has been in multiple studies, and treatment of SIBO with antibiotics has been shown to improve symptoms, an effect that is difficult to explain any mechanism other than the gut-skin axis. The role of gut dysbiosis in acne, through the influence of gut bacteria on systemic androgen metabolism and sebaceous gland activity, is an area of active and productive research.
The ageing dimension
The gut-skin axis is not simply relevant to inflammatory skin conditions. It has an increasingly well-characterised role in skin ageing that is directly relevant to aesthetic medicine. Aging is frequently accompanied by a decline in microbial diversity and the loss of short-chain fatty acid-producing taxa — changes that weaken the intestinal barrier and contribute to the persistent low-grade inflammation described as . These microbial alterations contribute to low-grade chronic inflammation, oxidative stress, and impaired metabolic regulation, all of which are implicated in age-related .
The concept of inflammaging, the chronic, low-grade, inflammatory state that characterises biological ageing, is directly relevant here. Inflammatory cytokines, elevated systemically as a consequence of gut dysbiosis and intestinal permeability, activate the same matrix metalloproteinase pathways that UV radiation uses to degrade dermal collagen. The gut microbiome is, in other words, a second driver of the same collagen-destroying — one that operates independently of UV and that is not addressed by sunscreen or retinoids alone.
Diet as the most accessible intervention
The most practically significant aspect of the gut-skin axis, from a clinical perspective, is the degree to which dietary choices influence gut microbiome composition and through it, skin health. Diet, particularly Mediterranean and plant-based patterns, plays a critical role in modulating gut microbiota by enhancing beneficial microbes and their metabolic functions. In contrast, diets rich in saturated fats and processed foods promote dysbiosis and accelerate ageing.
Dietary fibre, from vegetables, legumes, whole grains, and fruit, is the substrate for SCFA-producing bacteria. A diet consistently low in fibre starves these bacteria of the they need, SCFA production and the downstream benefits for both gut and skin barrier function. Omega-3 fatty acids, found in oily fish and certain plant sources, have anti-inflammatory that operate in part through their influence on the gut microbiome. Polyphenols, found in berries, green tea, dark chocolate, and olive oil, are preferentially metabolised by beneficial gut bacteria, producing metabolites that further reduce systemic inflammation.
Ultra-processed foods, high-glycaemic diets, and alcohol all shift gut microbiome composition in directions that promote dysbiosis, increase intestinal permeability, and elevate systemic inflammatory markers, effects that have measurable downstream consequences for skin quality and accelerated skin ageing.
Probiotics and prebiotics — what the evidence supports
The commercial market for probiotic supplements has grown enormously on the back of gut-skin axis science and the claims made for many products significantly exceed what the evidence supports. It is worth being honest about this.
The evidence for specific probiotic strains in specific skin conditions is more developed than the evidence for general skin health or anti-ageing supplementation. Lactobacillus rhamnosus GG and Lactobacillus reuteri have the strongest evidence base for atopic dermatitis.
Certain Lactobacillus and Bifidobacterium strains have shown promise for rosacea. The evidence for oral probiotics producing general skin quality improvement in non-inflammatory skin is interesting but not yet robust enough to support confident clinical recommendation.
Dietary supplements including prebiotics along with probiotics have demonstrated significant potential in altering gut microbiota composition and, in turn, improving skin health, though the operative phrase is “significant potential” rather than established clinical efficacy across the board.
The more evidence-based recommendation, for the majority of patients a specific skin condition requiring targeted probiotic intervention, is dietary rather than supplemental: a fibre-rich, diverse, minimally processed diet that supports gut microbiome diversity through food rather than capsules. This is less commercially attractive than a probiotic supplement. It is considerably better evidenced.
The honest clinical summary
The gut-skin axis is not a fringe concept or a marketing construct. It is a well-characterised and rapidly developing area of science with genuine clinical implications for everyone working in dermatology and aesthetic medicine. The mechanisms connecting gut microbiome health to skin inflammation, skin function, and skin ageing are real, multiple, and increasingly well understood.
What the current evidence does not support is a simple, single intervention — take this probiotic, follow this diet — that produces measurable skin improvement in a healthy individual. The relationship is complex, individual, and modulated by genetics, lifestyle, and the specific composition of a patient’s gut microbiome in ways that current clinical tools cannot yet fully characterise.
What it does support is a clinical approach that takes diet and gut health seriously as genuine contributors to skin quality alongside the topical, injectable, and energy-based interventions we discuss elsewhere in this blog. The who wants to optimise their skin health at every level to them deserves a conversation that includes their gut as well as their face. That conversation, for most of us in aesthetic medicine, is one we have been too slow to have.
The views expressed in Clinical Perspectives are the Dr Forrester’s own and reflect his personal and professional experience in aesthetic medicine.
References
Zhao Y et al. The gut-skin axis: Emerging insights in understanding and treating skin gut microbiome modulation. International Journal of Molecular Medicine. 2025;56(6):210.
Jimenez-Sanchez M et al. The gut-skin axis: a bi-directional, microbiota-driven relationship with potential. Gut Microbes. 2025;17(1): .
Mota C et al. Unraveling the Gut-Skin Axis: The Role of Microbiota in Skin Health and Disease. .2025;12(4):167.
Kim JY. Gut Microbiota, Probiotics, and Aging: Molecular Mechanisms and Implications for Healthy Aging. Journal of Microbiology and Biotechnology. 2026.
Castillo M et al. Probiotics for skin aging and skin conditions in the elderly. Clinics in Dermatology. 2026.
Kopczyńska M et al. A review of short-chain fatty acids in gut and skin: Possible implications in skin aging. ScienceDirect. 2025.
Hussain A et al. A Comprehensive Review of the Triangular Relationship Among Diet, Gut Microbiota, and Aging. PMC. 2025.
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