Probiotics, Prebiotics, Postbiotics: What Fermented Skincare Really Means
Walk down any beauty aisle and you'll hear the same words: probiotic, microbiome-friendly, fermented. It sounds like your moisturiser has a tiny yoghurt culture living in it. Spoiler: it almost certainly doesn't, and it shouldn't.
Let's clear up the three "-biotics", and look at what's actually worth putting into a formula.
Your skin is a garden
Your skin hosts a busy community of bacteria, yeasts and other microbes. When that community is balanced, it helps keep skin comfortable and resilient. When it's disrupted, by harsh cleansing for example, skin can feel it. Hence the interest in ingredients that support the "garden" rather than scorching it.
The three -biotics, in plain English
- Probiotics are live microorganisms. Think of them as new plants for the garden.
- Prebiotics are food for the microbes already living there, usually specific sugars or fibres. Think fertiliser.
- Postbiotics are the useful stuff left behind: inactivated microbes and their components. The international scientific association ISAPP formally defined a postbiotic in 2021 as "a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host" (Salminen et al., Nature Reviews Gastroenterology & Hepatology). Think compost.
Why your "probiotic cream" is really postbiotic
Cosmetics have strict microbial limits. They're meant to be close to germ-free, which is exactly why they contain preservatives. So keeping billions of live bacteria happy in a jar just doesn't fit. A 2023 review of probiotic ingredients in cosmetics explains that brands therefore rely on ferments, lysates and filtrates instead (Molecules, 2023).
These are the ingredients you'll actually see on labels:
- Ferment filtrates: the liquid left after microbes ferment a plant or grain, then filtered. The K-beauty classic is Galactomyces Ferment Filtrate, and rice ferments like Aspergillus/Rice Ferment Filtrate follow the same idea.
- Lysates: microbes that have been broken open, releasing their components. Bifida Ferment Lysate and Lactobacillus Ferment Lysate are the best known.
- Fermented botanicals: familiar plants given a fermentation twist, like Cica Ferment Filtrate or Green Tea Ferment Filtrate.
- Prebiotics: sugars such as Inulin and Alpha-Glucan Oligosaccharide, meant to feed the helpful residents of your skin.
What does the science actually say?
Honest answer: it's promising and early. A 2023 review in Microorganisms notes that topical probiotic research is still at an early stage. Postbiotics are more stable and practical to formulate, but human evidence that they change the skin microbiome is still limited (De Almeida et al., 2023).
That's not a reason to skip them. Many ferments bring amino acids, peptides, organic acids and sugars that are lovely for skin feel and hydration. It's a reason to be careful with claims. "Supports a balanced skin feel" is fair. "Cures acne by fixing your microbiome" is not.
Formulating with ferments: a few friendly tips
- They still need a preservative. A ferment is rich in sugars and nutrients, and that's a feast for unwanted microbes too.
- Add them at cool-down in most cases, and check each ingredient's entry in the Ingredient Dictionary for its use level and pH window. Here's galactomyces and bifida lysate.
- Pair smart. Prebiotic + postbiotic in a gentle, low-surfactant cleanser or a simple essence is a great first project.
- Mind the smell. Some ferments have a faint "bready" note. That's normal.
Where to start exploring
Browse our Ferments & Postbiotics collection for the full range, or the Microbiome & Prebiotics collection if you want to build a "feed the garden" formula. Barrier-supporting partners live in Barrier Repair.
The garden metaphor holds up: you don't need to plant anything exotic. Mostly, stop scorching the soil and give it a little compost.