The Gut–Skin Axis: How Digestive Health Shapes Acne and Inflammation

Part one of a series on skin health from the inside out.

Introduction

Let's talk about the gut for a minute. It's trending for good reason, and it's often a big contributor to many chronic skin conditions. What you put on your skin and what you put in your body matter equally. You could be eating all the right things, but if you're using products that are too harsh for your skin, it isn't going to heal. On the other side, you could be using exactly the right products for your skin, but if you're stressed to the max and your hormones or underlying gut inflammation are driving the flare, the products alone may not resolve it either.

This is exactly why I believe in treating skin topically and internally, side by side, exploring how the gut microbiome influences your skin's health and resilience, as well as supporting the skin microbiome and skin barrier.

I'm Chloe, a BHSc-qualified, NHAA-registered naturopath based in Perth, working alongside a skin specialist at Laneway Skin. In clinic, this is the pattern I see constantly: skin that won't fully resolve until we look a little bit deeper, not instead of the topical side, but alongside it.

Everything shared here is for educational purposes only and isn't a substitute for individual medical advice. Always consult your healthcare professional about your own situation.

Why does gut health affect acne?

The gut–skin axis describes the bidirectional communication between intestinal microbiota and skin physiology. Disruption of the gut's protective lining can impair intestinal barrier function, allowing endotoxins and bacteria to enter the bloodstream. This affects skin homeostasis and is consistently associated with inflammatory skin conditions such as acne, eczema, and rosacea.

Image generated using Canva AI

 

That said, this connection isn't universal. Some people have no digestive symptoms at all, and their acne is being driven instead by hormone imbalances like oestrogen dominance or high androgens, or by something happening at the skin surface itself, triggered by products or environmental exposure. The gut is a major piece of the puzzle, not the whole picture.

Studies comparing people with acne to people with clear skin show that acne‑prone individuals often have a different gut microbiome profile.

Specifically:

Reduced microbial diversity → Fewer types of bacteria overall, which weakens gut resilience.

Higher Bacteroidetes : Firmicutes ratio → A shift toward bacteria associated with inflammation and metabolic imbalance.

More Proteobacteria → These are often “alarm‑signal” bacteria linked with inflammation and gut barrier disruption.

Less Actinobacteria → This group includes beneficial species that help maintain gut stability.

Loss of Lactobacillus and Bifidobacterium → These are your classic “good bacteria” that support digestion, immunity, and a healthy gut lining.

What is the skin microbiome, and why does it matter for acne?

The skin microbiome mainly consists of four bacterial phyla: Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria. Healthy skin maintains balance between commensal and pathogenic species. When dysbiosis occurs, an imbalance in abundance and diversity, pathogenic strains dominate, driving inflammation and barrier dysfunction.

Key commensals such as S. epidermidis and C. acnes (formerly Propionibacterium acnes) are essential for microbiome stability. Keratinocytes play a frontline role in detecting pathogens and maintaining immune balance.

New research insight: acne isn't caused by more C. acnes, but by specific high-virulence strains, particularly phylotype IA1, that trigger stronger immune responses. Metagenomic studies have found that it's the phylotype diversity of the C. acnes community that's reduced in acne lesions, specifically a drop in richness and evenness, rather than a simple change in overall abundance. These acne-associated phylotypes express more virulence factors, which can intensify local inflammation by activating the skin's innate and adaptive immune pathways. They also form dense biofilms, increasing resistance to treatment and promoting microcomedone formation. Meanwhile, S. epidermidis produces succinic acid and lipoteichoic acid, which inhibit C. acnes and calm inflammation, a good reminder that not all bacteria are harmful; some are guardians of skin health.

In short: it's rarely about "bad bacteria" alone. It's about balance, and which strains are dominant.

 

 

 

 

Is it bacterial acne, or could it be fungal acne?

Our skin isn't just home to bacteria, it also hosts fungi like Malassezia globosa. When this yeast overgrows, it can look and feel a lot like acne, but the cause (and treatment) are completely different.

Bacterial acne is driven by C. acnes, which thrives in oily, clogged pores and tends to show up as whiteheads, blackheads, or deeper cysts.

Fungal acne, on the other hand, is actually Malassezia folliculitis, small, itchy bumps that often appear on the chest, back, head or shoulders. It loves heat, sweat, and humidity, and can flare up after antibiotics or heavy skincare products.

The difference matters because knowing which one you're dealing with can save you months of frustration and help you finally treat your skin the right way.

What does a healthy skin barrier actually do?

The skin barrier provides physical, chemical, and immunological protection.

Its low surface temperature (29–34°C) and acidic pH (4.5–5.5) discourage pathogenic growth. The stratum corneum, made up of corneocytes and intercellular lamellar lipids (ceramides, cholesterol, fatty acids), supports antioxidant systems, antimicrobial peptide production, and immune activation.

Disruption of this barrier is seen in atopic dermatitis, psoriasis, rosacea, and acne vulgaris. Loss of normal barrier structure increases transepidermal water loss (TEWL) and inflammation. This is where topical treatment can work wonders in repairing and supporting an impaired skin barrier.

 

 

The gut–brain–skin connection

The gut and skin communicate through neuroendocrine pathways. Known as the body's "second brain," the gut has neuroendocrine connections where gut flora synthesise and release neurotransmitters such as serotonin, norepinephrine, and acetylcholine via the gut–brain axis. This stimulates nerve pathways and triggers hormone release from intestinal endocrine cells, producing widespread systemic effects, including inflammation.

Separately, psychological stress increases local production of substance P in the skin, and elevated substance P is linked to eczema, acne, and barrier dysfunction. So the connection runs both ways: your gut can influence your skin, and your stress response can influence your skin directly, through a shared neuroendocrine network. This creates a feedback loop where stress, gut health, and skin inflammation perpetuate each other.

Mechanistic depth for those who want the details, gut microbes produce short-chain fatty acids (SCFAs) that regulate T-cells and reduce inflammation. Dysbiosis can increase intestinal permeability, activate effector T cells, and disrupt the balance between those cells and regulatory T cells, allowing bacterial metabolites to enter circulation and activate mTOR signalling, a pathway linked to excess sebum production and cell proliferation that helps drive acne.

In short: stress and gut imbalance aren't separate problems from your skin, they're feeding the same inflammatory loop from two directions at once.

What actually drives acne? (it's not just bacteria)

Acne is multifactorial. It can be driven by:

• Hormonal imbalances (oestrogen dominance, androgen excess, insulin resistance)
• Gut dysbiosis and immune activation (potential pathogens aswell)
• Nutrient deficiencies (vitamin D, iron, zinc)
• Environmental triggers (UV, pollution, harsh products)
  
• + so much more

When certain strains of C. acnes interact with the skin, they switch on key immune sensors including toll‑like receptors (TLR‑2 and TLR‑4) and the NLRP3 inflammasome. This sparks the release of inflammatory messengers like IL‑1β, IL‑6, IL‑8 and TNF‑α, and drives Th17/Th1 immune activity.

In simple terms, these pathways show that acne isn’t just about hormones or bacteria, it’s a chronic inflammatory condition rooted in an over‑activated immune response.

Why conventional treatment alone often falls short

The standard treatment pathway for acne includes isotretinoin for severe cases, hormonal contraceptive pills, or androgen antagonists such as spironolactone for hormonal acne or antibitoics. Many of these come with side effects that are genuinely hard to tolerate, and long-term antibiotic use raises the risk of antibiotic-resistant C. acnes.

None of this means these treatments don't have a place. It means they're often treating the presentation without addressing what's driving it , which is where a complementary approach can help.

 

Nutritional and probiotic interventions that support the gut–skin axis

A 2024 systematic review (33 studies, n = 2,112) found that prebiotics, probiotics, and postbiotics modulate the gut–skin axis and microbiome, and may be advantageous in managing acne vulgaris as a complementary approach to traditional therapies.

Definitions:

• Prebiotics: non-digestible food components that feed beneficial gut bacteria.
• Probiotics: live microorganisms that benefit the host when given in the right amounts.
• Postbiotics: inactivated microbial components that still exert biological effects without needing to be alive.
  

 

Key nutrients for skin health

Nutrition plays a central role in calming inflammation and supporting the gut–skin axis.

Key nutrients:

• Zinc: supports wound healing and reduces inflammation
• Vitamin D: modulates immune function
• Omega-3s: soothe inflammatory pathways
• Antioxidants: protect skin cells from oxidative stress
  

Avoid overly restrictive diets. Small, consistent changes matter most.

 

Clinical insight

In consults, I assess:

• Gut patterns
• Hormone drivers
• Nutrient deficiencies
• Inflammation triggers 
  
• Nutrition 
  
• + So much more

 

This isn't guesswork. Where it's clinically relevant, I use microbiome mapping and functional pathology testing to see what's actually happening rather than treating blind. Many of the women I see in the clinic tell me the relief isn't just in their skin calming down, it's in finally understanding what's been driving it, instead of cycling through products and guessing.

If your symptoms feel confusing or unpredictable, personalised support can make things much clearer. Working alongside a skin specialist means we can address what's happening on the skin's surface while I investigate what might be driving it from within: gut health, hormones, inflammation, stress physiology, and nutrient status. Neither side of that equation replaces the other. They work together.

Consults are available via telehealth or in-person at Laneway Skin, Osborne Park, Perth.

So... Can gut health cause acne?

It can contribute to acne sometimes significantly but it’s rarely the sole cause and research has indicated gut health as a contributing factor or correlation as opposed to a direct cause. Think of it as one of several interconnected systems that influence skin inflammation.

For many people, supporting gut health helps calm breakouts, reduce inflammation, and improve treatment outcomes.

 

Final Words,

Your skin is a reflection of your internal health, and healing begins when we listen to what it's trying to tell us. You don't need to figure it out alone.

This is the first in a series where I'll be working through skin health from the inside out, one piece at a time. Next month, how hormones show up in skin.

Let me know if there's a topic you want covered in the comments below. 

Share it with someone who's tried everything for their acne, see you in the next post!

Chloe 

Botanika Naturopathy 

BHSc (Naturopath) M.Biomedicine (candidate)

 

 

 

 

Frequently asked questions

Can gut health really cause acne? Not for everyone, but for many people, yes. Research consistently links gut dysbiosis to inflammatory skin conditions including acne, though hormones and skin-surface factors can also be the primary driver, sometimes with no gut symptoms at all.

How do I know if my acne is fungal or bacterial? Fungal acne (Malassezia folliculitis) tends to be small, itchy, uniform bumps, often on the chest, back, or forhead, and it doesn't respond to standard antibiotic-based acne treatment. If you've tried everything without success, it's worth having this properly assessed rather than continuing to guess.

Do I need to see a naturopath and a dermatologist? They're not mutually exclusive. My approach is to work alongside a skin specialist, addressing the skin's surface and what's driving things internally at the same time, rather than treating either in isolation.

 

 References + Further Reading

Borrego-Ruiz, A., & Borrego, J. J. (2024). Nutritional and Microbial Strategies for Treating Acne, Alopecia, and Atopic Dermatitis. Nutrients, 16(20), 3559. https://doi.org/10.3390/nu16203559

De Pessemier, B., Grine, L., Debaere, M., Maes, A., Paetzold, B., & Callewaert, C. (2021). Gut–Skin Axis: Current Knowledge of the Interrelationship between Microbial Dysbiosis and Skin Conditions. Microorganisms, 9(2), 353. https://doi.org/10.3390/microorganisms9020353

Li, X., & Jin, J. (2025). The Mechanism and Research Progress of Skin Microbiota in Pathogenesis of Acne. Dermatology Research and Practice, 2025, 9910076. https://doi.org/10.1155/drp/9910076