What Are Postbiotics For Skin?

Postbiotics are the compounds beneficial bacteria produce when they ferment an ingredient — peptides, organic acids, enzymes and cell fragments that your skin can use directly. Unlike probiotics, postbiotics do not need to be alive to work, which is why postbiotic skincare is shelf-stable and never needs refrigerating.

What exactly is a postbiotic?

The formal definition comes from the International Scientific Association of Probiotics and Prebiotics, which in 2021 published a consensus statement defining a postbiotic as "a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host."¹

Two words in that sentence are doing the heavy lifting. Inanimate — the organisms are no longer alive. And and/or their components — what you get includes the microbial material itself, not only the molecules it left behind.

Fermentation is how you get there. Live cultures meet a raw material — a plant extract, say — and as they feed, they break big molecules into smaller ones and build new compounds that were never in the starting material. Peptides. Organic acids. Enzymes. Antioxidants. Then the cultures are switched off. What remains is the fermented material: the metabolites, plus the spent cells and cell fragments. That mixture is the postbiotic. If the skin microbiome is new to you, The Biome Crowd™ is a good place to start.

There is no agreed standard for what "postbiotic" means in skincare. The ISAPP definition was written for food and supplements, where it is still being worked out.^1,2 Beauty has nothing equivalent: no regulator, no industry body, no shared rule about what has to be in a bottle before the word "postbiotic" can go on the front of it.

This is why the ingredient list is so important. It's the only place you get the facts about a product, without any marketing to influence or dazzle you.

For example, take two that look almost identical. Lactobacillus/Carica Papaya fruit ferment and Lactobacillus/Carica Papaya fruit ferment filtrate differ by one word, and by what is physically in the bottle.

A ferment is the whole fermented material: the molecules the bacteria produced — peptides, organic acids, enzymes — together with the inactivated bacterial cells and their fragments. A filtrate has been through a filter. The dissolved molecules pass through. The cell material does not.

The ISAPP definition reads "inanimate microorganisms and/or their components" precisely because the cell material counts as part of the postbiotic, not as leftovers from making it. The papaya ferment is a good illustration: its ceramide and defensin signalling travels on extracellular vesicles, which are particles rather than dissolved molecules. What a filter does to them depends entirely on the filter.

So a ferment gives you everything the fermentation made. A filtrate gives you the part that fitted through. Neither is useless, and plenty of good formulas use filtrates — but they are not the same ingredient, and only one of them meets the definition. No label is obliged to explain that to you, which is why it is worth knowing.

How are postbiotics different from probiotics?

Probiotics are live organisms. Postbiotics are what live organisms make. The practical difference is survival.

For a topical probiotic to do anything at all, the organisms have to still be alive when the product reaches your face. That means surviving manufacture, the preservative system that stops the product spoiling, a warehouse, a courier in an Australian summer, and however many months the jar sits in your bathroom. Preservatives are designed to kill microorganisms. They are not fussy about which ones.

Postbiotics skip the problem. They are the end product rather than the thing that has to survive long enough to make it. Nothing has to stay alive, so nothing can quietly die on the way to you.

What do postbiotics do for the skin barrier?

The research associates topical ferments with improved barrier function and hydration.^4,5 That is the honest limit of what can be said, and we will not stretch it further than it goes.

A 2026 review in Cosmetics looking at prebiotics, probiotics and postbiotics in skincare concluded that postbiotics are the most practical of the three for topical formulation — stable, straightforward to preserve, and not dependent on anything staying alive — while noting that the evidence base is still developing.³

So: postbiotics are associated with supported barrier function, better hydration, and a more balanced surface environment for your skin's own microbial population. A solid foundation for a strong skin barrier.

Which postbiotics are used in skincare?

This is where most articles on postbiotics stop short, because naming the ingredients means having them. There are currently four across the SKINPOSSIBLE range, all fermented with Lactobacillus before they are formulated.

 

Why four rather than one? Because they are not interchangeable. The licorice ferment is an antioxidant and works on the look of redness. The papaya ferment is a signalling ingredient — it prompts your skin to make more of its own ceramides rather than purely relying on ours. The pineapple ferment exfoliates enzymatically, which is a gentler route to the same place than an acid. The aloe ferment hydrates and settles things down. Put differently: one of them calms, one of them instructs, one of them lifts away what doesn't need to be there, and one of them holds water. A formula built on a single ferment can only do one of those jobs, however good that ferment is.

The SKINPOSSIBLE High Achiever Super Serum carries three of the four — licorice, papaya and pineapple — alongside 4% niacinamide. The SKINPOSSIBLE Get Fresh Calming Cleanser uses the aloe ferment. The SKINPOSSIBLE Let's Start Over Barrier Repair Soufflé uses papaya and aloe together with squalane and a three-ceramide complex.

And note what all four say on the label: ferment, not ferment filtrate. Per the distinction above, that is deliberate.

Do postbiotic products need refrigerating?

No. Postbiotic skincare is shelf-stable at normal room temperature, because there is nothing living in it that needs keeping alive.

Store it the way you would any skincare — out of direct sun, away from a hot car or a sunny windowsill, lid on. Use within 12 months of opening, or up to 24 months unopened somewhere cool and dark, like your bathroom cupboard.

Are postbiotics suitable for sensitive skin?

Generally, yes — and if your skin is the dramatic sort, the more useful question is what else is in the bottle.

In our own consumer trial of 50 participants with self-identified sensitive skin, aged 25–55, over three to six weeks: 100% of participants using the SKINPOSSIBLE Get Fresh Calming Cleanser reported experiencing no irritation, 94% using the SKINPOSSIBLE High Achiever Super Serum reported a reduction in visible redness, and 96% using the SKINPOSSIBLE Let's Start Over Barrier Repair Soufflé reported that visible dryness was reduced and their skin felt softer. These are participants' own assessments of their own skin, not clinical measurements, and we report them as exactly that.

The wider point: no ingredient earns the word gentle on its own if it turns up alongside fragrance, essential oils or drying alcohols. Postbiotics suit reactive skin because they are mild in themselves, and because they sit comfortably in a short, low-irritant formula. Everything we leave out is on our Nothing Possibly Problematic™ list.

How long do postbiotics take to work?

Expect a gradual change rather than a dramatic week. Postbiotic formulas tend to work more steadily than active-led routines, which is usually what you want when your skin has been taking offence at everything.

Not sure where to start? Take our skin quiz, or browse the postbiotic skincare range.

References

1. Salminen S, Collado MC, Endo A, et al. The International Scientific Association of Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of postbiotics. Nature Reviews Gastroenterology & Hepatology. 2021;18(9):649–667. doi:10.1038/s41575-021-00440-6 ↩ ↩²

2. Aguilar-Toalá JE, Arioli S, Behare P, et al. Postbiotics — when simplification fails to clarify. Nature Reviews Gastroenterology & Hepatology. 2021;18:825–826. doi:10.1038/s41575-021-00521-6 ↩

3. The Skin Microbiome Revolution: The Science and Challenges of Prebiotics, Probiotics, and Postbiotics in Skincare. Cosmetics. 2026;13(1):43. doi:10.3390/cosmetics13010043 ↩

4. Lee J, et al. Cera-Glow, ferment lysates of Lacticaseibacillus rhamnosus IDCC 3201, improves skin barrier function in clinical study. Journal of Cosmetic Dermatology. 2023. doi:10.1111/jocd.15642 ↩

5. Effects of a lotion containing probiotic ferment lysate as the main functional ingredient on enhancing skin barrier: a randomized, self-control study. Scientific Reports. 2023;13. doi:10.1038/s41598-023-43336-y ↩