Fermented Ingredients in K-Beauty

Fermentation is the quiet engine of the Korean kitchen. Cabbage becomes kimchi (making kimchi), soybeans become meju and then doenjang and ganjang (making jang), and cooked rice with nuruk becomes makgeolli (making makgeolli). The broader idea is covered in fermented foods. Because Korean eaters grow up treating microbes as ingredients, products advertised as fermented sound natural to Korean shoppers.

From the crock to the bottle

In cosmetics, fermentation means growing yeasts or bacteria on a base material, such as rice, soy or a plant extract, then filtering or processing the result. Labels often say ferment filtrate or ferment lysate. A 2022 overview in Molecules describes these bioferments as materials made by fermenting natural raw materials with selected microbes, and reports that fermentation can break large molecules into smaller ones. Its examples include fermented red and black ginseng and soybean.

Two kinds of ingredient come up often:

• Yeast ferment filtrates, such as Galactomyces ferment filtrate, a skincare ingredient made by fermenting with a yeast.
• Rice and makgeolli by-products. Rice ferments and makgeolli lees, the solids left after pressing, appear in some masks and cleansers.

What the research shows

Evidence varies by ingredient, and much of it is tied to companies.

• Galactomyces ferment filtrate. A 2023 study followed 86 women in Japan who used three skincare products containing it twice daily for 12 months. Measures of wrinkles, spots and roughness improved. But it had no placebo or comparison group, compared women with their own measurements from 11 years earlier, and most authors worked for the manufacturer of the products tested. It cannot show that the filtrate caused the changes.
• Makgeolli. A 2013 Korean study tested an alcohol extract of one makgeolli made with herbs, using enzymes and cell lines in the lab. It suggested possible whitening, anti-wrinkle and anti-inflammatory activity in those systems; no people or animals were tested. No human study of makgeolli lees on skin was found.
• Fermented ingredients generally. The 2022 Molecules review is a narrative overview, not a systematic review. It says human evidence for bioferments is sparse and based on small samples, that some headline figures come from single studies, and that several claims rest on patents or trade publications.

So the common claim that fermented skincare is more absorbable or more potent than ordinary skincare remains largely unproven: independent comparisons of fermented and unfermented versions of the same ingredient are scarce.

A food idea, not a food benefit

Eating fermented food and using fermented cosmetics are different things. Research on kimchi or jang on the plate says nothing about a lotion, and a cosmetic made with a fermented ingredient does not necessarily contain live microbes.

Cautions

• Patch-test. Fermented products can irritate like any other cosmetic. Try a small area for a day first.
• Check allergens. Ferments may be made from rice, soy, wheat or other foods, so read labels if you have a food allergy.
• Treat marketing numbers with care. Percentages on packaging usually come from the company's own tests.

Fermentation is a lovely thread connecting the pantry and the dressing table. It is perhaps best appreciated as culture and craft, with the science still catching up. For more, see K-beauty vocabulary and the rise of K-beauty.