What Is Lactobacillus/Streptococcus Thermophilus/Soybean Ferment Filtrate?
Lactobacillus/Streptococcus Thermophilus/Soybean Ferment Filtrate is a skin friendly liquid that comes from fermenting soybeans with two well known probiotic bacteria, Lactobacillus and Streptococcus thermophilus. During fermentation the microbes break down soybean proteins into smaller peptides and amino acids while releasing vitamins, antioxidants, sugars and soothing fatty acids. This cocktail of nutrients is then filtered to remove the living bacteria, leaving behind a clear or slightly amber fluid that is gentle on skin.
Soy fermentation has long been part of traditional food making, but its cosmetic use took off in the early 2000s when brands began exploring probiotics for skin care. Researchers noticed that the by-products of fermentation could hydrate and calm the skin without the stability issues of live cultures, so formulators started adding the filtrate to moisturizers and anti aging lines.
To make the ingredient, non-GMO soybeans are cooked and mixed with a nutrient solution. The prepared beans are inoculated with carefully selected strains of Lactobacillus and Streptococcus thermophilus, then kept at a warm, controlled temperature for one to two days. After fermentation the mixture is pressed and filtered to remove solids and microbes, tested for purity and finally blended with water or glycerin to reach the desired concentration for cosmetic use.
You will most often see this filtrate in hydrating serums, lightweight lotions, sheet masks, overnight masks, soothing post-sun gels and barrier repair creams. It is also popular in multi-step K-beauty routines and clean beauty formulas that highlight plant and probiotic sources.
Lactobacillus/Streptococcus Thermophilus/Soybean Ferment Filtrate’s Cosmetic Benefits/Uses
This ingredient is prized for one main job in skin care.
Skin conditioning: The filtrate helps skin stay soft, smooth and comfortable. Its mix of amino acids and sugars binds water to the skin surface for an immediate hydration boost, while the gentle fatty acids reinforce the natural moisture barrier, reducing dryness and flakiness. Over time regular use can improve skin texture, support a balanced microbiome and leave the complexion looking healthier and more resilient.
Who Can Use Lactobacillus/Streptococcus Thermophilus/Soybean Ferment Filtrate
This ferment filtrate is considered gentle enough for most skin types. Dry, sensitive and mature complexions tend to benefit the most thanks to the hydrating amino acids and barrier-supporting lipids, while oily and combination skin can still enjoy the lightweight feel because the ingredient is water-based and non-greasy. It may be unsuitable only for people with a confirmed soy allergy, as residual soy proteins could trigger irritation.
The ferment is produced from soybeans and probiotic bacteria, with no animal-derived substances involved, so it is acceptable for vegans and vegetarians.
Current research shows no hormonal or systemic concerns for pregnant or breastfeeding women when the ingredient is used topically in cosmetics. This is not medical advice and anyone who is expecting or nursing should run all personal care products past a qualified doctor to be on the safe side.
The filtrate does not make skin more sensitive to sunlight and can be used both morning and night. It also layers well with most common actives, including vitamin C and niacinamide, without stability issues.
Potential Side Effects/Adverse Reactions
Side effects from topical Lactobacillus/Streptococcus Thermophilus/Soybean Ferment Filtrate can vary from person to person. The points below list potential reactions although most users will not encounter them when the ingredient is properly formulated and used as directed.
- Redness, itching or swelling in individuals with a soy allergy
- Mild stinging or warmth on very compromised or freshly exfoliated skin
- Rare cases of contact dermatitis due to sensitivity to fermentation by-products
- Breakouts in extremely acne-prone skin if combined with occlusive formulas that trap sebum
If any of these reactions occur discontinue use immediately and seek advice from a healthcare professional.
Comedogenic Rating
Rating: 0 / 5
Lactobacillus/Streptococcus Thermophilus/Soybean Ferment Filtrate is a water based liquid with very little oil or wax content, so it does not block pores or sit heavily on the skin. The molecules it contains are mostly small amino acids, sugars and light fatty acids that absorb quickly and rinse away cleanly, which is why it earns a solid zero on the comedogenic scale.
Suitable for acne-prone and breakout-prone skin.
Keep in mind that the overall pore friendliness of a finished product also depends on the other ingredients in the formula. If the filtrate is paired with rich butters or heavy silicones the product’s final comedogenicity could change.
Summary
Lactobacillus/Streptococcus Thermophilus/Soybean Ferment Filtrate is first and foremost a skin conditioner. By delivering amino acids, sugars and gentle fatty acids it pulls water into the skin for instant hydration, helps rebuild the moisture barrier for lasting smoothness and supports a balanced surface microbiome for calmer looking skin.
The ferment has found a niche in K-beauty serums, sheet masks and clean beauty moisturizers, yet it is not as widely used as classics like hyaluronic acid or glycerin. Those who do try it often become fans of its light feel and quick soothing effect.
Topical use is considered very safe for most people with the main caution being a possible reaction in anyone allergic to soy. As with any new skincare ingredient it is wise to patch test a small area first just to be sure your skin is happy with it.