The skincare industry has moved through probiotics, prebiotics, and is now enthusiastically embracing postbiotics. If the terminology feels like marketing, it’s partly because it’s being used that way. But postbiotics are also a genuine scientific concept with real skin applications that, in some ways, make more practical sense for topical skincare than live probiotics.
Probiotics, prebiotics, and postbiotics: the basics
In the context of the microbiome (whether gut or skin), these three terms refer to different components of the same system:
Probiotics are live microorganisms (beneficial bacteria or yeasts) that, when present in adequate amounts, confer a health benefit. In food, these are the live cultures in yogurt, kefir, and fermented vegetables. In topical skincare, applying live bacteria to the skin is the concept, though significant challenges exist around keeping them alive in a cosmetic formulation.
Prebiotics are substances that selectively feed and support beneficial microorganisms. In skincare, these are typically specific carbohydrates, polyphenols, or other compounds that certain beneficial skin bacteria can use as food, theoretically supporting their growth and activity over less desirable strains.
Postbiotics are the products of microbial fermentation and metabolism: the non-living cellular components (cell wall fragments, proteins, lipids), metabolites (short-chain fatty acids, organic acids, enzymes), and bioactive compounds produced when bacteria do their metabolic work. When fermentation happens and produces beneficial outputs, those outputs are the postbiotics.
Why postbiotics may be more practical for skincare than live probiotics
A fundamental challenge with live probiotic skincare is stability. Living bacteria need specific conditions to survive: appropriate temperature, pH, moisture, and the absence of preservatives (which kill bacteria indiscriminately). A cosmetic product that contains effective preservatives to remain safe, which it must, is not an ideal environment for live bacteria.
Many products labeled as containing probiotics may have minimal live bacteria by the time they reach the consumer, depending on manufacturing conditions, storage, and shelf life. Some contain fermented ingredients rather than live bacteria, which is actually closer to postbiotic than probiotic.
Postbiotics bypass this problem entirely. Because they’re non-living compounds rather than live microorganisms, they don’t need to be kept alive, don’t require special preservation considerations, and can be standardised for consistent active compound content. A postbiotic ingredient is stable in ways that live bacteria are not.
What postbiotics do for skin
The research on postbiotics for skin is developing quickly and is genuinely interesting. Several mechanisms have been identified:
Barrier support: certain postbiotic compounds, particularly those from Lactobacillus strains, have been found to strengthen skin barrier function by stimulating ceramide synthesis in keratinocytes and reducing transepidermal water loss. A 2020 study found that a specific Lactobacillus ferment filtrate improved skin barrier integrity and reduced sensitivity in subjects with reactive skin.
Anti-inflammatory effects: postbiotics from various beneficial bacteria have demonstrated anti-inflammatory activity, reducing the production of pro-inflammatory cytokines when applied topically. This is relevant for acne-prone skin, sensitised skin, eczema, and rosacea, all conditions with an inflammatory component.
Antimicrobial activity: some postbiotic compounds, including bacteriocins (small proteins produced by bacteria that inhibit competing bacteria) and short-chain fatty acids, can inhibit pathogenic microorganisms on the skin. This includes Staphylococcus aureus (relevant to eczema) and Cutibacterium acnes (relevant to acne).
pH regulation: the organic acids produced during fermentation (lactic acid, acetic acid) can contribute to maintaining the skin’s naturally acidic pH, which supports the beneficial skin microbiome and barrier function.
Common postbiotic ingredients in skincare
Lactobacillus ferment filtrate is one of the most commonly used postbiotic ingredients. The filtrate contains the metabolites and cellular components produced during lactobacillus fermentation. Studies have shown it improves skin hydration, reduces sensitivity, and has mild antimicrobial properties.
Bifida ferment lysate is produced from Bifidobacterium bifidus fermentation. It appears in several well-known anti-aging and sensitive skin products and has studies showing improvements in skin hydration and barrier function.
Saccharomyces ferment filtrate (yeast ferment filtrate) contains enzymes and proteins from yeast fermentation. It has antioxidant properties and has been used for skin brightening applications.
Lactic acid, while now often synthesised, is a natural postbiotic compound from Lactobacillus fermentation. It’s the most commonly used AHA in skincare, with exfoliating, hydrating, and barrier-supporting properties.
Fermented ingredients as a broader category
Beyond specifically labelled postbiotics, fermented plant ingredients represent a broader application of postbiotic principles. Fermented rice water, fermented soy extract, and other fermented botanical preparations contain the postbiotic compounds produced during fermentation (including acids, enzymes, and metabolites) along with the transformed plant compounds from the fermentation substrate.
Fermentation often increases the bioavailability of plant compounds: the breakdown of cell walls during fermentation releases compounds that were previously trapped, and microbial enzymes can convert precursor compounds into more active forms. This is why some fermented extracts have different and sometimes more potent activity profiles than their unfermented equivalents.
Realistic expectations
Postbiotics are a genuine and interesting category in skincare. They’re not a cure for skin conditions, but they have credible mechanisms for barrier support, inflammation reduction, and microbiome balance. The research is newer than for established ingredients like retinoids or vitamin C, so the evidence base is still building.
Products that contain well-researched postbiotic ingredients like Lactobacillus ferment filtrate or bifida ferment lysate at meaningful concentrations, combined with other well-supported barrier and anti-aging ingredients, represent a genuinely thoughtful formulation approach. Look for these in combination with known actives rather than as the sole “hero” ingredient in a routine.