The Gut-Skin Axis in Chronic Inflammatory Disease
If you struggle with eczema, psoriasis, or other chronic skin flares, you know how frustrating and unpredictable they can feel. You may have tried creams, medications, or elimination diets — only to find that symptoms return. For many people, the skin is not the root of the problem, but a reflection of deeper immune and inflammatory processes happening inside the body.
Emerging research on the gut-skin axis suggests that the health of the gut microbiome plays a meaningful role in chronic inflammatory skin disease. The gut microbiome helps regulate inflammation throughout the body. Beyond digestion and nutrient absorption, it influences immune activation, intestinal permeability, gut barrier function, and even neurotransmitter production. What we eat, how often we eat, and even the state of our nervous system during meals can influence how effectively nutrients are absorbed and utilized for healing.
The gut and skin are closely connected through immune signaling, detoxification pathways, and inflammatory regulation. Changes in the gut microbiome are often reflected in the skin, particularly in chronic inflammatory conditions such as psoriasis and atopic dermatitis (AD). What is happening on the skin is often a reflection of what is happening inside the gut.
The Microbiome and Inflammatory Skin Diseases
There are hundreds to thousands of bacterial species living throughout the gastrointestinal tract, with different populations residing in the small and large intestine. These microbes help regulate immune balance by maintaining equilibrium between pro-inflammatory and anti-inflammatory pathways.
In psoriasis and eczema, common trends in gut dysbiosis include:
Increased Firmicutes and certain inflammatory-associated taxa
Decreased Bacteroidota and Proteobacteria
Reduced beneficial species such as Akkermansia muciniphila and Faecalibacterium prausnitzii
An altered Firmicutes/Bacteroidota (F/B) ratio, which has also been associated with cardiometabolic risk
These microbial shifts may reduce the production of short-chain fatty acids (SCFAs), including butyrate and propionate. SCFAs are essential for maintaining immune tolerance, supporting regulatory T cell (Treg) function, and preserving gut barrier integrity. Regulatory T cells (Treg) are responsible for calming the immune system after it has completed its purpose in fighting off pathogens or diseases. Chronic inflammatory diseases are often associated with reduced regulatory T cell function.
Dietary patterns (lower refined grains, higher fruits/vegetables) are associated with increased microbiome diversity and overall metabolism, leading to a healthier gut microbiome and thus healthier skin.
Gut dysbiosis may contribute to chronic, relapsing inflammatory disease through:
Increased intestinal permeability
Activation of pro-inflammatory cytokines (TNF-α, IL-6, IL-17, IL-23)
Imbalance between regulatory T cells (Treg) and Th17 cells
Reduced SCFA production
Systemic immune activation as bacterial components enter circulation
Reduced butyrate-producing bacteria may impair gut barrier integrity and promote inflammatory immune signaling, potentially contributing to psoriasis and atopic dermatitis progression.
Modulating the microbiome using probiotic strains such as Lactobacillus and Bifidobacterium has been associated with:
Reduced pro-inflammatory cytokines
Improved skin barrier function
Decreased psoriasis severity
Improved quality of life
Short-Chain Fatty Acids and Immune Regulation
Approximately 70–80% of the body’s immune cells reside in the gut. There is constant communication between intestinal microbes, the epithelial barrier, and the mucosal immune system.
Beneficial microbes help maintain colonization resistance by:
Competing with pathogens
Strengthening the mucus layer
Supporting epithelial integrity
Importantly, microbial metabolites can enter circulation and influence immune activity in distant tissues, including the skin.
Fermentable fibers from vegetables, fruits, legumes, and whole grains are metabolized into SCFAs (butyrate, acetate, propionate). These compounds:
Promote regulatory T cells (Tregs)
Enhance mucus and antimicrobial peptide production
Strengthen barrier integrity
Reduce pro-inflammatory cytokines
Neurotransmitters and the Gut-Brain-Skin Connection
The gut and brain communicate constantly, and this connection can influence both stress levels and skin inflammation. Neurotransmitters regulate mood, pain perception, motility, immune signaling, and intestinal barrier function. Many are produced not only by host tissues but also influenced by gut microbes. Microbial metabolites such as SCFAs can influence neurotransmitter synthesis and signaling, linking gut health to nervous system function.
Serotonin
Approximately 95% of serotonin is produced in the gut, primarily by enterochromaffin (EC) cells from tryptophan. Serotonin regulates intestinal motility, digestive enzyme secretion, visceral (organ) sensation and pain, mucosal inflammation and gut lining permeability. Too much serotonin can lead to abdominal pain, diarrhea and hypersensitivity. Too little serotonin can lead to constipation and impaired barrier function.
Dopamine
Dopamine regulates appetite, motivation, reward pathways, cognition systemically, gut motility, and gut permeability. It is produced both within the brain and the gut. In animal models, reduced microbiome diversity has been associated with altered dopamine signaling and increased anxiety-like behavior. In animal studies, probiotics have been linked to increased dopamine concentration in the brain and reduced anxiety levels.
GABA
Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter, which means it is very calming to our nervous systems. It is used in many diseases associated with pain as a natural analgesic. Several Bifidobacterium and lactobacillus species produce GABA in the gut. Animal studies show that a limited microbiome diversity consequently leads to decreased levels of GABA.
Histamine
This neurotransmitter is produced from the amino acid, histidine, via the gut lining and microbes. Histamine supports immune activation, inflammation, gut permeability, and gut motility. Histamine acts through multiple receptor subtypes throughout the body, producing different effects depending on location. For example, histamine can stimulate digestive enzyme secretion in the gut, while in other tissues it may influence pain perception and inflammatory signaling.
Intestinal Permeability (“Leaky Gut”) and Systemic Inflammation
The intestinal lining plays a critical role in regulating inflammation throughout the body. It is made up of a single layer of tightly packed cells that form a protective barrier between the contents of the gut and the bloodstream. These cells are held together by structures called tight junctions, which function like seals, carefully controlling what is allowed to pass through. Under healthy conditions, nutrients are absorbed efficiently while bacteria, toxins, and large food particles remain contained within the gut.
However, chronic inflammation can weaken this barrier. Research shows that inflammatory signaling molecules such as TNF-α and interferon-γ can alter the proteins responsible for maintaining tight junction integrity, increasing intestinal permeability (often referred to as “leaky gut”). When gut barrier function becomes compromised, substances that are normally contained within the digestive tract may enter circulation, amplifying immune activation and contributing to systemic inflammation.
Several factors contribute to this breakdown in barrier integrity. Gut dysbiosis, along with bacterial components such as lipopolysaccharide (LPS), can stimulate immune responses that further disrupt tight junctions. Chronic psychological stress has also been shown to increase intestinal permeability through stress hormone signaling pathways. In addition, frequent NSAID use, alcohol intake, and dietary patterns high in inflammatory fats may impair the protective lining of the gut over time. When this process becomes persistent, the immune system may remain in a heightened state of activation, a pattern often seen in chronic inflammatory conditions.
Because the immune system communicates continuously between the gut and the skin, prolonged increases in intestinal permeability may influence inflammatory signaling in skin conditions such as eczema and acne. Chronic immune activation may contribute to systemic inflammation and heightened immune reactivity. During flares of chronic inflammatory disease, individuals may experience increased food sensitivities.
In some individuals with persistent flares, targeted dietary trials may help identify symptom triggers. A temporary elimination trial under professional guidance eliminating dairy, gluten, refined sugars, and processed foods for three weeks and then reintroducing one category at a time while tracking symptoms may help clarify reactivity patterns. Refined sugars and processed foods are generally inflammatory and without nutritional benefit so should be removed for long-term health.
Gut Soothing Foods
The digestive tract contains multiple organs and is over 25 feet long. It requires a lot of energy, enzymes, blood flow, and hormone regulation. Strategic dietary support can assist in restoring gut barrier integrity and microbial balance.
Supportive foods for gut restoration
Fermented foods (sauerkraut, yogurt, kimchi)
Broth (bone, veggie, chicken)
Lightly steamed vegetables
Low sugar
Fermented foods help support beneficial microbial balance and reduce overgrowth of less favorable species. Broth is high in glutamine, a molecule that helps seal and strengthen the gut lining. Lightly steamed vegetables help break down the fiber that is hardest to digest on its own. Fiber breaks down into short-chain fatty acids, which are great supportive foods for our commensal bacteria and help maintain a healthy microbiome. Sugar can feed improper bacteria balances and may promote microbial imbalance in some individuals.
Addressing the gut microbiome, supporting intestinal barrier integrity, and regulating immune activation may represent an important upstream strategy in managing chronic inflammatory skin conditions. A personalized approach that includes dietary modification, microbiome support, and nervous system regulation can help restore balance within the gut-skin axis.
