For decades, skincare has cast bacteria as the enemy, with cleansers promising to wipe them away and that tight, squeaky feeling after washing taken as proof that skin was truly clean. Research over the past fifteen years tells a gentler story. Your skin has always been home to a living community of microbes, called the skin microbiome, and that community quietly helps your skin stay comfortable and resilient. It also changes as we move through our 40s and 50s, in ways skincare marketing rarely mentions, and understanding how it changes has shaped the way I think about cleansing, toning and every bottle I make.
I spent the past few weeks reading the studies behind the headlines, because the skin microbiome has become one of the most talked about topics in skincare, and a lot of what gets said about it goes further than the research does. Some of it is solid and useful, some of it is early, and some of it is mostly marketing, so I want to walk you through all three honestly.
→ Your skin does not need to be sterile to be clean. It needs to be comfortable.
We will start with who actually lives on your skin, then look at why your skin's acidity matters, what changes as we get older, what tends to throw things off, how to read microbiome skincare labels, and how to support your skin microbiome with a routine that works with it instead of against it.
What Is the Skin Microbiome?
Your skin microbiome is the community of bacteria, fungi and viruses that live on the surface of your skin. Researchers have spent years mapping it, and one of the first things they found is that your skin is not one neighborhood but many. Oily areas like your forehead host different residents than moist folds or drier spots like your forearms.
What surprised me most is how hard the skin surface is to live on. It is dry, low in nutrients and slightly acidic, which makes it a tough place for unwelcome microbes to settle, while the residents that belong there have adapted to it. [1]
A few of the regulars are worth knowing by name.
Staphylococcus epidermidis. One of the most common residents of healthy skin. Its cousin Staphylococcus aureus gets most of the bad press, but epidermidis is considered part of normal, comfortable skin.
Cutibacterium acnes. Despite the unfortunate name (it used to be called Propionibacterium acnes), this is a normal resident of healthy skin that lives in oily areas, because it feeds on the oils your skin makes. Keep it in mind, because it plays a big part in what changes after 40.
Corynebacterium. A group of bacteria that prefer the moist areas of the body.
Malassezia. A yeast, and the most common fungus on skin, especially in oily areas.
Why Skin pH Matters to the Microbes Living on Your Face
That slightly acidic surface is one of the ways your skin keeps the right microbes comfortable and the wrong ones out. [1] It is also something your routine can nudge in either direction. Tap water and many soaps and cleansers sit above skin's natural pH, so after you wash, your skin spends a while finding its way back.
This is exactly why I care about skin pH when I formulate, and why toner has a real job in a Sanbe routine. The Chamomile Niacinamide Toner is formulated at a pH of 5.5 to 6, close to skin's natural range, so it gives your skin a hydrating, balancing step right after cleansing. Press it in with your hands rather than a cotton pad so every drop reaches your skin. I wrote more about that in This Toner Has One Job, and if you live somewhere with hard water, Is Hard Water Hurting Your Skin? is worth a read too.
How the Skin Microbiome Changes With Age
Here is the part almost nobody talks about, and it is the reason I wanted to write this post. You will often read that the skin microbiome becomes less diverse as we get older. The research I found says the opposite.
A 2022 study in the Journal of Investigative Dermatology looked at the skin of 158 women ranging from their early 20s to their early 70s, sampling the face, forearm and buttock. Bacterial diversity actually increased with age at every site, while Cutibacterium, the oil loving resident, declined everywhere they looked, along with Lactobacillus. The researchers also found that the oil glands themselves got smaller with age, and those changes tracked with the shifts in bacteria. [2]
In other words, the community on your skin reorganizes itself around what your skin is producing. When there is less oil, the residents that depend on it make room for others. More diversity sounds like a good thing, and it may be, but researchers do not yet know whether this shift is helpful, harmful or simply different. What it does tell us about the skin microbiome and aging is that skin in its 40s and 50s is living by a different set of rules than it did at 25, and a routine built for oily 25 year old skin may not be what it needs now.
What Disrupts the Skin Microbiome and the Skin Barrier
Before you worry about every product in your cabinet, here is the reassuring part. A 2026 review in Skin Research and Technology looked at how cosmetics affect the skin microbiome and concluded that most well formulated everyday products do not cause major disruption in healthy skin. Your moisturizer is not quietly wiping out the residents on your face.
Where things tend to go sideways is in how we use products. Harsh, high pH cleansers, washing until skin squeaks, frequent scrubbing and stacking several strong actives at once all wear on the skin barrier, and the skin barrier and microbiome rely on each other, since the microbes live on the surface the barrier creates. [3] I covered the barrier side of this in Skin Barrier 101, and the short version is the same here: a struggling barrier almost always wants less, not more.
For everyday cleansing, the Sensitive Skin Foaming Face Wash is the one I reach for most because it cleans without that tight feeling afterward. At night, the Calming Cleansing Balm melts into a soft milk as you add water, so the day rinses away without any scrubbing.
Probiotic Skincare and Other Microbiome Skincare Labels, Explained
Walk down any skincare aisle and you will see probiotic, prebiotic and postbiotic printed on the labels. Here is what each one means.
Prebiotics. Ingredients meant to feed the helpful microbes already living on your skin.
Probiotics. Live microorganisms.
Postbiotics. What microbes leave behind, meaning the substances they produce or cells that are no longer alive.
The same 2026 review found that early studies on these ingredients look promising, but the evidence is limited by small studies, inconsistent designs and the fact that there is still no agreed standard for what a microbiome friendly claim actually means. [3] So when a label makes that claim, it could mean very different things depending on the brand.
There is also a practical problem I learned about in my formulation training with Formula Botanica. Keeping live bacteria alive in a jar of skincare is genuinely difficult, so many products labeled probiotic actually contain lysates, which are broken down bacterial cells rather than living ones. That does not make them useless, but it is worth knowing what you are paying for. Is probiotic skincare worth it? For most people, I would call it an interesting option rather than a necessity, and a gentle, consistent routine does more of the work.
If you are curious about the other side of this conversation, how the microbes in your gut relate to your skin, our guest post from Marie Vollmar, The Gut-Skin Connection, goes into that topic.
How to Support Your Skin Microbiome With a Gentle Routine
This is where you get to take a breath. Supporting your skin microbiome does not require new products. It mostly asks you to do less, more consistently, so here is how I would approach it in phases, so it never feels like an overhaul.
Phase one, the first two weeks: simplify. Pare your routine back to a gentle cleanser, a toner pressed in with your hands, a moisturizer and your daily sunscreen. Pause scrubs and anything that leaves your skin feeling tight or stingy. If you are unsure what goes where, The Skincare Layering Order walks through it step by step.
Phase two, weeks three to six: stay steady. Resist the urge to add anything new. If you use an oil based serum like the Beloved Serum, it goes on last at night, after your water based steps, so it can seal everything in. Water-Based vs Oil-Based Serums explains why that order matters.
Phase three, after 30 to 48 days: check in. Your skin renews itself roughly every 30 to 48 days, so give it one full cycle before deciding how a gentler routine is working. After that, add one thing at a time, if you add anything at all. I explain why consistency matters so much in this post on the missing link.
→ Less scrubbing and more consistency covers most of the microbiome advice that holds up.
What Menopause Changes About the Microbes on Your Face
For a lot of us, the first thing we notice in perimenopause is not a wrinkle. It is that our face simply is not as oily as it used to be, and the T-zone that needed blotting papers in our 20s now feels tight by mid afternoon.
That change in oil seems to reach the skin microbiome too. A 2024 pilot study in Frontiers in Aging compared healthy women before and after menopause whose ages were, on average, only about 12 years apart. The postmenopausal women had less Cutibacterium and more bacterial diversity on their faces, even though measures of skin elasticity were no different between the two groups. [4] That suggests menopause itself, and not only the passing years, plays a part. It is a small, early study, and its authors work for a cosmetic ingredient company, so I hold it loosely, but it lines up with the larger aging research above.
In practice, this is a season to protect the oil and moisture your skin still makes. Skip stripping cleansers and lean on hydration and comfort. The Chamomile Niacinamide Toner followed by the lightweight Anti-Aging Turmeric Cream is a pairing I often suggest here, because skin feels hydrated, balanced and soft without a heavy routine. If hormonal shifts are new territory for you, Why Your Skin Is Reacting to Hormonal Fluctuations goes further into that.
What is the skin microbiome?
Your skin microbiome is the community of bacteria, fungi and viruses living on the surface of your skin. Oily, moist and dry areas each host different residents, and most of them are harmless or helpful, taking up space so unwelcome visitors have a harder time settling in.
Is all the bacteria on my skin bad?
Not at all. Residents like Staphylococcus epidermidis and Cutibacterium acnes are normal on healthy skin, despite the second one's name. Researchers see them as part of how skin stays comfortable, which is why stripping everything away was never the goal.
Does the skin microbiome change with age?
Yes, though not in the way most people expect. In a study of women from their 20s to their 70s, the bacteria on older skin became more varied, while the oil loving Cutibacterium declined as oil glands shrank.
Does skin pH really matter?
It seems to. Your skin's surface is naturally slightly acidic, which helps make it a tough place for unwelcome microbes to settle. That is why I pay attention to pH when I formulate, and why a balancing toner after cleansing has a real job in a routine.
Can my skincare routine damage my skin microbiome?
Most well formulated products do not cause major disruption in healthy skin. The trouble tends to come from habits like harsh, high pH cleansers, frequent scrubbing and layering too many strong actives, which wear on the barrier the microbes live on.
How often should I wash my face?
For most people, what you wash with matters more than how often. Once or twice a day with a gentle cleanser is plenty, and if your skin feels tight or squeaky afterward, the cleanser may be stronger than your skin needs.
Should I use probiotic skincare?
Go in with curious, realistic expectations. Early studies look promising, but they are small and varied, and there is no agreed standard for microbiome claims yet. A gentle, consistent routine does more of the work than any single probiotic product.
What is the difference between prebiotics, probiotics and postbiotics?
Prebiotics feed the microbes already on your skin, probiotics are live microbes, and postbiotics are the substances microbes produce or cells that are no longer alive. All three are being studied, but the human evidence is still catching up with the marketing.
What does "microbiome friendly" mean on a label?
Honestly, there is no agreed standard for that phrase yet, so it can mean very different things from brand to brand. The most meaningful version is simply that a product does not disturb the community already living on your skin.
Can what I eat affect my skin?
That is the gut-skin connection, and it is a bigger topic than this post can cover. Our guest post from Marie Vollmar, The Gut-Skin Connection, walks through it if you want to explore that side.
How long until I notice a difference after simplifying my routine?
Your skin renews itself roughly every 30 to 48 days, so give it one full cycle before deciding whether a gentler routine is working. Changing products every week makes it hard to know what your skin is actually responding to, which I explain in Skin Barrier 101.
The Honest Summary
Your skin was never meant to be sterile. The research on the skin microbiome is still young, but the parts that hold up all point in the same direction: keep your skin's slightly acidic surface comfortable, cleanse gently, give your routine time to work, and stay a little skeptical of labels that promise more than the studies show. And if your skin feels different in your 40s and 50s than it did at 25, that is not your imagination. The community living on it has changed too.
If you are not sure which products fit your skin right now, take the Sanbe skin quiz and I will point you to a simple starting place.
Pin the Your Skin Microbiome After 40 Blog post to Pinterest for later.
Sources
- Nature Reviews Microbiology | The Human Skin Microbiome
- Journal of Investigative Dermatology | Aging-Associated Changes in the Adult Human Skin Microbiome and the Host Factors that Affect Skin Microbiome Composition
- Skin Research and Technology | Cosmetic Interventions for Skin Microbiome Modulation: Current Strategies and Future Directions
- Frontiers in Aging | Menopause and Facial Skin Microbiomes: A Pilot Study Revealing Novel Insights Into Their Relationship