Skin Microbiome & Eczema
One bacterium is dominating your skin. And it's not supposed to.
Written by Milieu Science Team
If you have eczema, you already know the routine. Steroid creams during flares. Heavy moisturizers. Avoiding triggers. Managing it. Living with it.
What most people with eczema are never told: the condition has a specific microbial signature. And the treatments most commonly prescribed can make that signature worse.
The S. aureus Problem
In healthy skin, Staphylococcus aureus accounts for a small fraction of the bacterial community. In people with atopic dermatitis — the most common form of eczema — S. aureus can make up 90% of the bacteria present during a flare.
This isn't a coincidence. It's the mechanism.
S. aureus produces toxins and enzymes that directly attack the skin barrier. It degrades filaggrin — the structural protein that holds the skin's “brick and mortar” together. When filaggrin breaks down, ceramide levels drop, transepidermal water loss increases, and the barrier becomes permeable. Irritants get in. Moisture gets out. More S. aureus enters the skin, triggering further immune activation.
The result is the inflammation, weeping, and intense itch that define eczema flares. Not a mystery. A cascade.
The Vicious Cycle
What makes eczema so persistent is how the dysbiosis reinforces itself.
A healthy microbiome has natural S. aureus suppressors. Staphylococcus epidermidis and Roseomonas mucosa both produce compounds that directly inhibit S. aureus colonization. They compete for adhesion sites on skin cells. They signal the immune system to stay calibrated rather than overreacting.
When these species are depleted — by topical steroids, antibiotics, harsh cleansers, or simply the inflammatory environment itself — S. aureus fills the void. It dominates. Diversity collapses. And a collapsed microbiome means the immune system loses its teachers. It starts overreacting to everything. The sensitivity threshold drops. Triggers multiply.
This is eczema: not just a barrier problem, not just an immune problem, but a microbial collapse that causes both the barrier and the immune system to malfunction together.
What Testing Reveals
The key question in eczema-prone skin isn't just “do you have S. aureus?” Almost everyone does. The question is: what's the ratio? And what protective species are still present?
Milieu's sequencing maps your microbial community in detail. We look at S. aureus colonization levels, the presence and abundance of protective suppressors, and your overall diversity — a proxy for immune stability.
Some eczema profiles are driven primarily by S. aureus dominance. Others show an almost sterile barrier with extremely low overall diversity. Both present as eczema. Both require completely different approaches.
Without understanding your microbiome, you're navigating eczema-prone skin in the dark.
Learn more about how microbiome testing works →
Why This Data Matters for Eczema-Prone Skin
Supporting eczema-prone skin with microbiome science means understanding the protective ecosystem, not just patching the barrier.
Research shows that products for eczema-prone skin should be fragrance-free and minimal in preservatives — many of which are antimicrobial and further deplete protective species. The goal is to create conditions where S. epidermidis and Roseomonas can re-establish themselves, using barrier-supporting lipids that mimic the natural ceramide signaling these bacteria normally provide.
Avoiding ingredients that further collapse diversity and keeping formulations simple gives the microbiome the space it needs to shift — as protective species return and S. aureus levels drop, the skin ecosystem becomes more resilient over time.
FAQs
Commonly asked questions about this topic.
Eczema is associated with differences in the types and balance of bacteria present on the skin.
Bacteria imbalance in eczema may be influenced by reduced microbial diversity and overrepresentation of certain microbes.
Staphylococcus aureus is a common skin bacterium often found in higher levels on eczema-prone skin.
Changes in microbial balance may influence inflammation and overall skin behavior.
Eczema symptoms can fluctuate due to environmental triggers, skin barrier function, and microbial balance.
Recurring flare-ups, sensitivity, and changes in skin condition may be associated with microbial shifts.
Common triggers include stress, climate, skincare products, and overall skin condition.
Put this into practice
Your skin is its own ecosystem. The fastest way to see what's actually living on yours — and what your routine should look like — is the Superbiome microbiome test.
