Lactobacillus/Soymilk Ferment: What Is It, Cosmetic Uses, Benefits & Side Effects

Curious about this ingredient? In this article we're explaining exactly what it is and why it's used within cosmetic formulations.
Updated on: July 1, 2025
Share:
Inside this article:

We verify all information on this page using publicly available nomenclature standards from The Personal Care Products Council (PCPC), the European Commission's CosIng database and documentation provided directly by ingredient manufacturers. Our analysis is based on technical data from these sources to ensure accuracy and reliability.

What Is Lactobacillus/Soymilk Ferment?

Lactobacillus/Soymilk Ferment is a plant based ingredient that comes from letting the friendly bacterium Lactobacillus transform plain soymilk through controlled fermentation. During this process proteins, sugars and lipids in the soymilk break down into smaller molecules such as peptides, amino acids and simple sugars that skin can easily recognize and use. The idea of using fermented plant extracts in beauty care grew out of traditional food fermentation practices in East Asia, where people noticed that these preparations left hands smooth after handling them. Cosmetic chemists later explored this link, and by the early 2000s they began adding fermented soy to moisturizers and spa style masks.

To make the ingredient, makers start with non GMO soybeans, grind and cook them into soymilk, sterilize the liquid, then add a pure culture of Lactobacillus. After a set time at a warm temperature the mixture is filtered and preserved, yielding a mildly acidic liquid rich in skin friendly components. It turns up most often in leave-on and rinse-off products that aim to hydrate and soothe such as sheet masks, lightweight day creams, anti aging serums, after sun gels and scalp tonics.

Lactobacillus/Soymilk Ferment’s Cosmetic Benefits/Uses

This fermented soy extract brings several helpful roles to modern skincare formulas:

  • Humectant – attracts water from the environment and from deeper skin layers to the surface, helping keep the complexion plump and reducing the look of fine lines
  • Skin conditioning – softens and smooths by supplying amino acids and peptides that support the skin barrier, leaving it feeling comfortable

Who Can Use Lactobacillus/Soymilk Ferment

This fermented soy extract suits most skin types including dry, normal, combination and oily because it adds lightweight hydration without leaving a greasy film. Sensitive skin generally tolerates it as the fermentation process reduces many of the larger soy proteins that can be irritating, though anyone with a known soy allergy should proceed carefully or avoid it.

Because the ingredient is derived entirely from non animal sources and no animal by-products are used during fermentation, it is considered suitable for both vegans and vegetarians.

Topical use is also regarded as safe for people who are pregnant or breastfeeding, since the ingredient works on the surface of the skin with minimal chance of systemic absorption. This is not medical advice and anyone who is pregnant or nursing should show the product to a qualified healthcare provider before adding it to a routine just to be safe.

Lactobacillus/Soymilk Ferment does not make skin more prone to sunburn, so it is not known to cause photosensitivity. As with all humectants it works best when paired with an occlusive moisturizer and daytime sunscreen to keep the newly attracted water from evaporating.

Potential Side Effects/Adverse Reactions

Responses to Lactobacillus/Soymilk Ferment can differ from one person to another. The points below list possible side effects, yet most users will not encounter them when the ingredient is formulated and used correctly.

  • Allergic contact dermatitis – people with a soy allergy may notice redness, itching or swelling
  • Mild stinging or warmth – very sensitive skin can feel a brief tingle when the product is first applied due to its slightly acidic pH
  • Breakouts – although uncommon the extra moisture may trigger blemishes in acne-prone skin if a formula also contains heavier oils or occlusives
  • Eye irritation – products that migrate into the eyes can cause watering or burning
  • Product spoilage – if the preservative system fails live microbes could multiply leading to odor or skin irritation

If any discomfort, rash or other adverse effect appears stop using the product and seek advice from a healthcare professional

Comedogenic Rating

Rating: 1 / 5

Lactobacillus/Soymilk Ferment is a watery, low oil material that mainly supplies small peptides, sugars and amino acids. It does not leave a heavy film or clog pores on its own which keeps the rating near the bottom of the scale. A touch of natural soy lipids may remain after fermentation yet the amount is far below the level that typically triggers blackheads or whiteheads.

Suitable for acne-prone skin in most formulations, although the final product’s overall pore-clogging potential depends on the other ingredients it is blended with.

If paired with thick butters, waxes or high levels of silicone the total formula could feel heavier than the ferment itself would suggest so always look at the full ingredient list.

Summary

Lactobacillus/Soymilk Ferment serves mainly as a humectant and skin-conditioning agent. The fermentation process breaks large soy proteins into bite-sized peptides and sugars that pull in water and help reinforce the skin barrier, leaving the surface soft, smooth and comfortably hydrated.

While not as famous as hyaluronic acid or glycerin the ferment is gaining steady traction in K-beauty inspired lotions, masks and scalp mists thanks to its vegan roots and gentle profile.

Overall safety is high with very few reported reactions beyond those linked to a true soy allergy. As with any new skincare ingredient it is wise to patch test a fresh product on a small area first to make sure your skin agrees with it.

Was this article helpful?
More from Glooshi:
ADVERTISEMENT
Get all our top headlines in beauty.
Delivered right to your inbox each week. Zero spam, all goodness, opt-out at anytime.
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Get the latest beauty news, top product recommendations & brand-exclusive discount codes direct to your inbox.
Send good feedback:

All feedback is greatly appreciated, anonymous, and will be used to improve the quality of our articles.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Send bad feedback:

All feedback is greatly appreciated, anonymous, and will be used to improve the quality of our articles.

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Search