What Is Lactobacillus/Eel Skin/Butylene Glycol Ferment Filtrate?
Lactobacillus/Eel Skin/Butylene Glycol Ferment Filtrate is a skin care ingredient produced by fermenting eel skin in a base of butylene glycol with the help of the probiotic microorganism Lactobacillus. During fermentation, proteins, amino acids and natural sugars from the eel skin break down into smaller, skin-friendly molecules that dissolve in the moisturizing solvent butylene glycol. This creates a light, water-like filtrate rich in humectant compounds and conditioning peptides.
Eel-derived materials have long been prized in parts of East Asia for their high collagen content. As Korean beauty labs began exploring marine and aquatic sources for skin care, researchers applied fermentation techniques to eel skin to boost its bioavailability and shelf stability. Pairing it with Lactobacillus made the ingredients milder and easier for skin to accept while butylene glycol ensured good texture and penetration. The resulting filtrate entered commercial use in the late 2010s, first appearing in niche K-beauty sheet masks and quickly expanding into wider product lines.
To produce it, cleaned and finely minced eel skin is submerged in pharmaceutical-grade butylene glycol, inoculated with a controlled strain of Lactobacillus then left to ferment under specific temperature and pH conditions. After several days, the mixture is filtered to remove solids and sterilized to eliminate any live bacteria, yielding a clear or faintly amber liquid that formulators can blend directly into water-based phases.
You will most often find Lactobacillus/Eel Skin/Butylene Glycol Ferment Filtrate in hydrating sheet masks, lightweight gel moisturizers, daily serums aimed at strengthening the skin barrier, soothing after-sun products and anti-aging formulations that promise plumpness and a dewy finish.
Lactobacillus/Eel Skin/Butylene Glycol Ferment Filtrate’s Cosmetic Benefits/Uses
This multitasking ferment supports both immediate hydration and long-term skin comfort.
- Humectant: Pulls water from the environment and the deeper layers of skin to the surface, giving an instant plumping effect and reducing the look of fine lines
- Skin conditioning: Supplies peptides and amino acids that soften rough patches and improve overall texture for a smoother touch
- Emollient: Leaves a light, non-greasy layer that helps seal in moisture and makes the skin feel silky without clogging pores
Who Can Use Lactobacillus/Eel Skin/Butylene Glycol Ferment Filtrate
This ferment filtrate is light enough for oily or combination skin yet hydrating enough for normal and dry complexions. Its humectant action draws in water without leaving a greasy film so even acne prone skin usually tolerates it well. Those with highly reactive or compromised barriers should introduce it slowly because the natural proteins released during fermentation could still provoke sensitivity in rare cases.
Because the source material comes from eel skin the ingredient is not suitable for vegans or vegetarians who avoid animal derived inputs. Consumers who keep kosher or halal may also wish to verify whether the finished product meets their specific standards.
No data suggests that the filtrate poses special concerns for women who are pregnant or breastfeeding. That said this is not medical advice and anyone who is expecting or nursing should check with a healthcare professional before adding new products to a routine.
The ingredient does not make skin more prone to sunburn so it is considered non photosensitising. It layers well with most common actives such as niacinamide and hyaluronic acid and it will not pill under sunscreen or makeup.
Potential Side Effects/Adverse Reactions
Responses to topical Lactobacillus/Eel Skin/Butylene Glycol Ferment Filtrate differ from person to person. The points below list potential side effects that might occur although most users experience none of them when the ingredient is formulated and stored correctly.
- Redness or stinging in very sensitive skin due to natural peptides and fermentation by products
- Contact dermatitis triggered by butylene glycol in individuals who are specifically sensitive to glycols
- Allergic reaction in people with fish or seafood allergies because trace eel proteins may remain
- Transient flushing if applied to freshly exfoliated or compromised skin barriers
If irritation or any other negative effect develops stop use immediately and consult a qualified medical professional.
Comedogenic Rating
Rating: 1 out of 5. Lactobacillus/Eel Skin/Butylene Glycol Ferment Filtrate is mostly water soluble and lightweight, so it does not sit heavily on the surface or trap oil in pores. Butylene glycol has a very low tendency to clog pores and the peptide rich eel skin fragments are small enough after fermentation that they rinse away easily. For these reasons the overall likelihood of causing blackheads or whiteheads is minimal. In short, it is generally considered safe for acne prone skin. If you already know you react poorly to glycols you might still want to avoid it.
Summary
Lactobacillus/Eel Skin/Butylene Glycol Ferment Filtrate acts as a humectant, skin conditioner and emollient. The fermentation process breaks eel skin proteins into amino acids and peptides that draw water into the upper layers and smooth rough texture, while butylene glycol keeps the liquid thin and easy for skin to absorb. A light emollient film then helps lock that moisture in place without feeling greasy.
The ingredient is still a niche player, most common in Korean beauty masks and gel creams, yet it is gaining attention among hydration focused products for its fresh texture and marine source story.
Overall safety data show a low irritation risk except in those sensitive to seafood proteins or glycols, making it a generally safe choice for daily use. As with any new cosmetic, do a patch test first so you can be sure your skin agrees with it.