What fermentation actually does to skincare ingredients: the science made simple

What fermentation does to skincare actives

Fermentation in skincare is a controlled microbial process that transforms raw botanical extracts into bioavailable compounds the skin can absorb more readily. The process breaks down large molecules into smaller fragments, increases antioxidant concentration, generates new compounds like amino acids and organic acids, and in some cases produces specific actives that do not exist in the unfermented substrate. Galactomyces ferment filtrate — a byproduct of Japanese sake brewing — is one of the most researched examples: the fermentation process produces kojic acid and alpha-hydroxy acids alongside high concentrations of vitamins and amino acids that improve skin texture, brightness and hydration simultaneously. The mechanism is different from simply adding a vitamin to a formula — fermented compounds interact with the skin's own microbiome and penetrate differently because of their reduced molecular size.

Vitamin C and fermentation: a stability solution

Pure L-ascorbic acid, the most potent form of vitamin C, is notoriously unstable — it oxidises rapidly on exposure to light and air, turning products yellow or orange and losing efficacy before the bottle is finished. Korean formulators addressed this through fermentation: the SOME BY MI Galactomyces Pure Vitamin C Glow Serum uses galactomyces ferment as both a brightening active and a stabilising environment for vitamin C. The fermentation byproducts create a more chemically stable context than standard water-based serums, which means the vitamin C retains its efficacy longer and causes less potential irritation than straight ascorbic acid at equivalent concentrations. The glow effect comes from both the vitamin C acting on melanin and the galactomyces improving surface texture and luminosity simultaneously.

Fermented eye care: why the delicate skin responds well

The skin around the eye is the thinnest on the face and has the lowest sebaceous gland density, which makes it both more vulnerable to dehydration and more responsive to fermented actives with small molecular weights. BENTON Fermentation Eye Cream uses a concentrated fermented complex — including yeast and plant ferments — that targets the fine lines, dark circles and loss of elasticity typical of the eye area. The fermentation process produces peptide fragments that signal collagen synthesis alongside amino acids that directly hydrate the stratum corneum. The result is a formula that works through multiple mechanisms simultaneously: structural support through collagen signalling, immediate hydration through amino acid delivery, and antioxidant protection through ferment-derived compounds. Applied nightly to clean skin, it complements the rest of the fermented routine without competing with any active.

Building a fermented routine that makes sense

The most effective way to use fermented actives is to layer them by texture: start with a light fermented toner or essence (like a galactomyces liquid), follow with a fermented serum for the primary concern (brightening or hydration), and finish with a richer fermented treatment for repair. Banila Co Treatment Essence works as the preparatory layer here — its fermented complex preps the skin's surface for the actives that follow, functioning as the "first essence" step in the Korean 10-step framework. A common mistake is expecting single-use results from fermented actives: these compounds work through gradual remodelling and microbiome support, and the visible changes in texture, tone and radiance typically emerge over four to eight weeks of consistent use.