Your skin carries a large population of bacteria, fungi, viruses and mites, and most of them are either harmless or useful. That's the whole of the settled science in one sentence. Everything past it gets murkier fast, which is why this post is about what the research shows, what it doesn't, and why no balm, mine included, can claim to balance your skin flora.
The terrain angle here comes from Andra Sitoianu, who writes The Bioavailable Naturopath on Substack. She's a certified naturopath, and her habit of reading microbes as a symptom of the conditions they live in rather than as invaders to be wiped out is the most useful thing I've read on this subject. In her Rosacea Guide she puts it plainly about mites: everyone carries them, and the question is what lets them dominate.
Below: what lives on skin, four claims worth doubting, and what changing your products can and can't do.
Where this comes from. This post draws on the public writing of Andra Sitoianu, The Bioavailable Naturopath, in particular The Rosacea Guide and My Topical Acne Toolkit. We paraphrase her framing, add the general research, and link her posts so you can read her in her own words; her paid guides carry her full protocols. Educational content, not medical advice.
What lives up there
Skin is a hard place to live. Byrd, Belkaid and Segre, writing in 2018, describe it as physically harsh, dry, nutrient poor and acidic, and colonized anyway by a diverse community that both shapes the immune system and is shaped by it. The cast you'll hear named most often is Cutibacterium acnes, Staphylococcus epidermidis and Staphylococcus aureus.
Where you sample matters more than almost anything else. Grice and Segre established that colonization follows the ecology of the surface: oily forehead, moist armpit and dry forearm host different communities on the same person. Most of what lives there is harmless or beneficial, and the relationship runs both ways, with skin immune responses shaping the microbes while the microbes help educate the immune system.
That two-way street is the part worth holding onto. It's why "kill the bad bugs" is an incomplete plan, and it's also why "feed the good bugs" is a marketing sentence rather than a mechanism.
Dysbiosis is a description, not a villain
Dysbiosis just means the community has shifted from what's typical. It doesn't say why, and it usually doesn't say which direction the causation runs. Two examples make the point.
Acne first. Cutibacterium acnes lives on nearly every adult face, chest and back. A 2023 review by Sa and colleagues makes the point that its presence isn't the issue: most people carrying it don't have acne, and it's phylotype IA1 that's associated with lesions. Acne looks less like an infection and more like a question of which strains are dominant and what the follicle around them is doing.
Eczema second. Kong and colleagues sampled 12 children with moderate to severe atopic dermatitis repeatedly through flares. Staphylococcus sequences, particularly S. aureus, rose during flares and tracked with severity, reaching 65% of sequences during untreated flares, and diversity climbed again with treatment, ahead of the skin looking better. Twelve children is a small cohort, and the design can't tell you whether S. aureus drives a flare or rides along with one. Both studies are worth knowing. Neither is a reason to buy anything.
| Organism | Where it lives | Associated with | What that does not mean |
|---|---|---|---|
| Cutibacterium acnes | Oily sites: face, chest, back | Acne lesions, specific phylotypes | That having it causes acne, or that eliminating it is the goal |
| Staphylococcus epidermidis | Most of the body surface | Normal colonization, immune signaling | That it is a "good bacteria" you can feed with a cream |
| Staphylococcus aureus | Nose, damaged or eczema-prone skin | Higher proportions during eczema flares | That it is the cause of eczema rather than part of the picture |
| Demodex mites | Hair follicles and sebaceous glands, face | Higher density in rosacea | That mites have been shown to cause rosacea |
The mite everyone is suddenly talking about
Demodex is having a moment online, and the underlying finding is real. A meta-analysis by Chang and Huang pooled 23 case control studies covering 1,513 people with rosacea and found infestation far more common than in controls, with an odds ratio of 9.039, and significantly higher mite density. The authors are careful about what that buys you: variability between studies was high, and case control designs cannot establish causation.
Andra's version of this in her rosacea guide is the terrain version. Everyone carries the mites; the question she asks is what conditions let them multiply. She also calls prescription topical ivermectin useful, and that's worth stating accurately: dermatologists prescribe topical ivermectin for papulopustular rosacea, it is a drug, and it belongs in a conversation with a clinician rather than in a post about balms. That is a prescription and a clinician's call. A balm does a different job.
Environment moves the community
Here's the observation that made me want to write this post. In a post on X, Andra noted that surfers' skin microbiomes look more like other surfers' than like those of non-surfers who live nearby. I went looking for a peer-reviewed source for that exact comparison and couldn't find one, so I'm giving you the observation as hers, from her post on X, and nothing more.
What is published is the neighbouring finding: Nielsen and Jiang, 2019, measured changes in the human skin microbiome after ocean water exposure. Swim in the sea, your skin flora shifts. That's a modest paper and it doesn't make the surfer comparison, but the general point stands on its own feet: what you spend your days touching, swimming in and breathing near shapes what lives on you, and it probably matters more than your cleanser.
What topicals can and can't rebalance
This is where money gets spent. Skin microbiome research is still at the description stage. The reviews above are sequencing studies. None of them shows that a cream, oil, balm or cleanser rebalances the skin microbiome, and no ingredient on a shelf has been shown to selectively feed the organisms you want while starving the ones you don't.
What products can do, and what actually changes microbial pressure, is more boring than that:
| What you'll see claimed | What's reasonable to say instead |
|---|---|
| "Balances your skin microbiome" | No product has been shown to do this; the measurement itself is a research tool |
| "Feeds your good bacteria" | Prebiotic claims for skin are marketing ahead of evidence |
| "Kills acne bacteria" | Antimicrobials reduce microbial load; the target organism lives on nearly everyone anyway |
| "Restores your acid mantle" | Gentle, low-stripping washing keeps surface conditions closer to normal; that's the real mechanism |
Andra's own boundaries in her topical acne toolkit are the sane ones, and she applies them to her own antimicrobial tools: patch test, stop if burning persists or redness increases, and when skin is inflamed, avoid scrubs, strong acids and stacking several new botanicals at once. Antimicrobials are tools for a period, not a permanent war footing. Anything strong enough to knock down one organism is usually strong enough to irritate the surface it lives on.
I've rendered, tested and worn more batches than I can count, and here's where my own product sits: a tallow balm is an occlusive emollient that slows water loss and doesn't strip. It doesn't kill anything, feed anything or rebalance anything, and it isn't a substitute for washing. If you want the full account of what the fat is, it's in the tallow for skin guide.
Levers that do change microbial pressure
The things most likely to matter aren't sold in the skincare aisle.
- Stop stripping. Harsh surfactants, hot water, aggressive exfoliation and alcohol toners change surface conditions daily, which is more pressure than any serum applies.
- Wash the things that touch your face. Pillowcases, phone screens, hats, towels and hands carry a share of what lands on you.
- Look at the mouth. Oral bacteria are swallowed constantly and the mouth is the opening of the digestive tract, which is Andra's framing and the subject of the oral microbiome post.
- Look at the gut. The strongest microbial links to skin disease in the literature run through the gut rather than the skin surface, which is the gut-skin axis post.
- Sleep and stress. Both change barrier function measurably, and the barrier is the habitat.
One caution about how "dysbiosis" gets used. In her binder guide, Andra lists skin dysbiosis, meaning eczema, psoriasis and acne, as one sign on a toxic burden checklist. That's a naturopathic framing device, not a finding, and I'd hold it loosely: eczema, psoriasis and acne each have their own well-described drivers, and reading all three as evidence of a single hidden burden can send you chasing the wrong thing for a year.
When it's a clinician's problem
Microbial curiosity stops where infection starts. Skin that's hot, swollen, spreading, weeping yellow crust, painful out of proportion or coming with a fever needs a licensed clinician now, not a reading list. The same goes for anything on or near the eye, and for rosacea or acne that's scarring, because scarring is the one thing you can't undo later. Naming a condition is fine; nothing here diagnoses one, and no jar I sell does either.
Questions we hear
Can I test my skin microbiome at home?
You can buy a kit, but the science isn't at the point where the result tells you what to do differently. Sequencing is a research tool, results shift with the body site, the season and the swab, and no published work links a consumer report to a course of action that improves skin.
Do probiotic skincare products work?
Some formulas are pleasant and well tolerated, and that's as far as the evidence goes today. There's no published demonstration that applying bacteria or their food to skin produces a stable, beneficial shift in the community living there.
Is washing my face twice a day bad for my microbiome?
Not by itself, and dermatologists generally advise washing gently up to twice a day and after sweating. What causes trouble is how you wash: very hot water, harsh cleansers, scrubs and toners strip lipids and change surface conditions far more than frequency does.
Does everyone have Demodex mites?
Essentially yes, in adults, and they live in follicles and sebaceous glands on the face. Density is higher in people with rosacea in the pooled research, which is an association, and it doesn't make mites the cause or make mite-killing products a first move.
Does tallow feed bacteria on skin?
There's no evidence that a tallow balm feeds or starves any particular skin organism, and I'd be suspicious of any brand claiming otherwise in either direction. It's an occlusive emollient: it slows water loss, softens and doesn't strip.
My skin got worse after I started an antimicrobial product. What now?
Stop it and let the skin settle, which is the boundary Andra sets in her own toolkit and a sensible one. Irritation looks a lot like "purging" and the difference matters, so if burning persists, redness increases or a rash appears, that's a stop signal rather than progress.
Go deeper
The series hub is Skin Terrain 101, and the orientation post is skin is downstream. For the habitat these organisms live in, read skin barrier repair 101. For the two upstream ecosystems that matter more than your cleanser, there's the gut-skin axis and the mouth as skin upstream, and the mite lane continues in rosacea through a terrain lens.
Sources
- Andra Sitoianu, The Bioavailable Naturopath (2026). The Rosacea Guide. Substack. Her Demodex and terrain framing; her recommendations are paywalled.
- Andra Sitoianu, The Bioavailable Naturopath (2026). My Topical Acne Toolkit. Substack. Her boundaries for antimicrobial topicals.
- Andra Sitoianu, The Bioavailable Naturopath (2025). Andra's Detox Binder Bible. Substack. The burden checklist that lists skin dysbiosis.
- Andra Sitoianu, The Bioavailable Naturopath. Surfers and skin microbiomes. X post, 2026. The surfer observation is hers; we found no peer-reviewed source for that comparison.
- Byrd AL, Belkaid Y, Segre JA (2018). The human skin microbiome. Nature Reviews Microbiology 16:143.
- Grice EA, Segre JA (2011). The skin microbiome. Nature Reviews Microbiology 9:244.
- Sa S, Fernandes R, Gestoso A, Macedo JM, Martins-Mendes D, Pereira AC, Baylina P (2023). Cutibacterium acnes Dysbiosis: Alternative Therapeutics for Clinical Application. Applied Sciences 13:12086.
- Kong HH, Oh J, Deming C and colleagues (2012). Temporal shifts in the skin microbiome associated with disease flares and treatment in children with atopic dermatitis. Genome Research 22:850.
- Nielsen MC, Jiang SC (2019). Alterations of the human skin microbiome after ocean water exposure. Marine Pollution Bulletin 145:595.
- Chang YS, Huang YC (2017). Role of Demodex mite infestation in rosacea: A systematic review and meta-analysis. Journal of the American Academy of Dermatology 77:441.
Brian is the founder of Craft Tallow, a small-batch tallow skincare line shipped from Cottonwood Heights, Utah, built on 100% grass-fed suet. Questions? Reply to any email from us; it lands with him.