Lash serum ingredients, explained
An ingredient list shouldn't require a chemistry degree. Here's what each key ingredient in a peptide lash serum actually does, in plain language, followed by every ingredient on our label.
Written by the Re:Cosm team · Last reviewed September 23, 2026 · Cosmetic information, not medical advice
The key ingredients
Acetyl Tetrapeptide-3 and Capixyl™
With red clover (Trifolium pratense) flower extract · Biomimetic peptide
A four amino acid peptide, acetylated for stability, that conditions the lash line and supports the look of fuller, denser lashes. It is the centrepiece of the prostaglandin-free approach.
Biotin
Vitamin B7, sometimes called vitamin H · Vitamin
A water-soluble B vitamin involved in keratin production. In a serum it works as a conditioning ingredient that supports stronger-looking, more resilient lashes.
Panthenol
Pro-vitamin B5 · Humectant and conditioner
A humectant that becomes vitamin B5 on skin and hair. It draws moisture into the lash, improving flexibility and reducing the brittleness that leads to breakage.
Hyaluronic Acid (Hydroxypropyl Trimonium Hyaluronate)
Cationic hyaluronic acid · Film-forming humectant
A modified hyaluronic acid with a positive charge, engineered to bind to hair fibres. It locks moisture onto the lash and forms a light protective film.
Centella Asiatica, Licorice Root and Houttuynia Cordata
Cica, dipotassium glycyrrhizate and eoseongcho · Soothing botanicals
Three calming ingredients from Korean skincare that keep the lash line comfortable with nightly use: centella asiatica, dipotassium glycyrrhizate from licorice root, and houttuynia cordata.
Read the full Centella Asiatica, Licorice Root and Houttuynia Cordata guide
Every ingredient on the label, decoded
This is the complete INCI list of Re:Cosm Lash Conditioning Serum in label order. Ingredients above about one percent are listed by concentration. Below that they can appear in any order, which is why the peptide complex sits at the end.
| Ingredient | What it does |
|---|---|
| Aqua | Water. The base of the gel and the solvent for everything else. |
| Betaine | Humectant derived from sugar beets. Draws moisture to skin and lashes. |
| Pentylene Glycol | Humectant and solvent that also supports the preservative system. |
| Glycerin | Classic humectant. Keeps the formula and the lash line hydrated. |
| Propanediol | Solvent and humectant that helps the gel spread evenly. |
| 1,2-Hexanediol | Humectant that boosts the preservative system, reducing the need for traditional preservatives. |
| Sodium Polyacryloyldimethyl Taurate | Gel former that gives the serum its texture so it stays on the lash line. |
| Butylene Glycol | Solvent and humectant. Also the carrier for several of the actives. |
| Hydroxyethylcellulose | Plant cellulose derived thickener. |
| Panthenol | Pro-vitamin B5. Hydrates and improves lash flexibility. |
| Xanthan Gum | Natural thickener from fermentation. |
| Dipotassium Glycyrrhizate | Soothing compound from licorice root. |
| Saccharide Isomerate | Plant sugar complex that binds moisture to skin. |
| Hydroxypropyl Trimonium Hyaluronate | Cationic hyaluronic acid that binds to lashes and holds moisture. |
| Ethylhexylglycerin | Skin conditioner that supports the preservative system. |
| Tromethamine | pH adjuster. |
| Disodium EDTA | Chelating agent. Binds trace minerals in water to keep the formula stable. |
| Centella Asiatica Extract | Cica. Soothing Korean skincare botanical. |
| Houttuynia Cordata Extract | Eoseongcho. Calming botanical. |
| Glycine Soja (Soybean) Seed Extract | Conditioning botanical extract. An extract, not an oil. |
| Biotin | Vitamin B7. Conditions and supports lash structure. |
| Disodium Phosphate | Buffer that keeps the pH steady. |
| Polysorbate 60 | Solubiliser that keeps plant extracts evenly dispersed in water. |
| Sodium Citrate | Buffer. |
| Citric Acid | pH adjuster. |
| Dextran | Carrier for the Capixyl™ complex. |
| Sodium Phosphate | Buffer. |
| Acetyl Tetrapeptide-3 | Biomimetic peptide at the centre of Capixyl™. |
| Trifolium Pratense (Clover) Flower Extract | Red clover, the botanical half of Capixyl™. |
What's deliberately not here
No prostaglandin analogs (see our guide on why), no fragrance, no parabens, no oils. For the delicate eye area, what a formula leaves out matters as much as what it puts in. The full list of names to watch for is in lash serum ingredients to avoid.
Common questions
What ingredients should a good lash serum have?
Look for conditioning ingredients with a clear role: a peptide such as Acetyl Tetrapeptide-3, humectants such as panthenol and hyaluronic acid, and soothing botanicals for the lash line. Just as important is what is missing: no prostaglandin analogs, no fragrance, and no oils if you wear extensions.
How do I read a lash serum ingredient list?
Ingredients above about one percent are listed from highest to lowest concentration. Below one percent they can appear in any order, which is why active peptides usually sit near the end. A brand that does not publish its full INCI list is worth avoiding.
Which lash serum ingredients are prostaglandins?
Names ending in -prost or containing prostenol or cloprostenate, such as isopropyl cloprostenate, bimatoprost and dechloro dihydroxy difluoro ethylcloprostenolamide. Isopropyl cloprostenate is prohibited in cosmetics sold in Canada.
Are peptide lash serums safe?
Peptide serums do not carry the documented side effects of prostaglandin analogs, such as iris darkening or fat loss around the eyes. As with any eye area product, stop use if you notice irritation.
More guides: lash serum after a lash lift, lash serum for sensitive eyes, Korean lash serums.
Sources and standards
Ingredient facts are checked against our published formula and the sources below. We describe how lashes look and feel, never growth: that is a drug claim, and our serum is a cosmetic.
See every ingredient
The complete INCI list for Re:Cosm Lash Conditioning Serum is published on the product page.
View the full formula