Ingredient Glossary
Every ingredient,
explained by the research
The actives in our four formulas: What each one is, what it actually does at the concentration we use, and where you’ll find it in the routine.
Ingredient Glossary
We formulate around what the science supports, not what sounds good on a label. Use this glossary to look up any ingredient in the Leiba routine, understand its mechanism, and see which products it appears in.
Brightening & Even Tone
Brightening · Vitamin B3
Niacinamide
A form of vitamin B3 shown to interrupt the transfer of pigment (melanosomes) to skin cells, supporting a more even-looking tone. We use it at 4% in the toner.
Brightening
N-Acetyl Glucosamine
NAG
An amino-sugar that works further upstream than niacinamide, addressing uneven tone closer to where melanin is produced. Pairs with niacinamide in the serum.
Brightening · Plant Active
Bearberry Extract
Arctostaphylos Uva Ursi
A natural source of arbutin, which inhibits tyrosinase, the enzyme that drives melanin synthesis, to help soften the look of dark spots.
Ferment Base
Galactomyces Ferment Filtrate
GFF
A yeast-derived ferment used as the base of the toner. The same active class found in much pricier essences. Supports barrier proteins and smoother-looking skin.
Barrier & Ceramides
Replenish Barrier
Ceramide Complex
Five barrier lipids, Ceramide NP, AP, EOP, Phytosphingosine and Cholesterol in a 2:1:0.001:1:1 ratio, that replenish the skin’s own barrier and help reduce water loss.
Barrier · Humectant
Ectoin
An extremophile-derived molecule that surrounds skin cells with a protective hydration shell, helping lower transepidermal water loss and support hydration.
Hydration Film
Snow Mushroom
Tremella Fuciformis
A polysaccharide that forms a flexible, non-sticky film and binds water comparably to hyaluronic acid, without pulling moisture from the skin in dry conditions.
Postbiotic
Fermented Bamboo
Lactobacillus / Arundinaria Gigantea Ferment
A probiotic ferment that produces postbiotic metabolites that support the skin microbiome and barrier.
Hydration & Humectants
Surface Hydration
Sodium Hyaluronate
The salt form of hyaluronic acid, drawing water to the skin’s surface for immediate, lightweight hydration alongside Snow Mushroom.
Pro-Vitamin B5
Panthenol
A humectant and emollient that supports fibroblast activity and replenishes the barrier, leaving skin softer and more comfortable.
Hydration Mechanism
GABA
Gamma-Aminobutyric Acid
Supports the skin’s own hydration pathways, upregulating aquaporin-3 and filaggrin expression to help skin hold onto moisture.
Marine Hydration
Laminaria (Kelp)
Laminaria Saccharina / Digitata
Brown seaweed rich in marine polysaccharides that support hydration through humectant and hydrocolloid mechanisms.
Antioxidants
Antioxidant
Astaxanthin
A marine-derived carotenoid and one of the most potent antioxidants used in cosmetic formulations. Up to 100× vitamin E for lipid peroxidation, per published data.
Vitamin E
Tocopherol
Naturally sourced vitamin E from sunflower and rosemary, working as an antioxidant to help defend skin lipids against oxidative stress.
Botanical Antioxidant
Rosemary Leaf Extract
Rosmarinus Officinalis
Source of carnosic acid and carnosol, two diterpene antioxidants that work through complementary mechanisms.
Polyphenol Antioxidant
White Tea
Camellia Sinensis
Rich in EGCG, a polyphenol antioxidant that helps protect skin against environmental oxidative stress.
Flavonoid Antioxidant
Rosehip
Rosa Canina
Delivers quercetin, rutin, and catechin, surface flavonoid antioxidants that help defend against daily oxidative stress.
Renewal, Peptides & Marine Botanicals
Gentle Exfoliation · PHA
Gluconolactone
A polyhydroxy acid (PHA) that exfoliates gently while acting as an antioxidant and supporting smoother texture. Milder than traditional AHAs.
Peptide · Collagen Signaling
Peptide Complex
Palmitoyl Tripeptide-1 + Tetrapeptide-7
A peptide duo that signals the skin’s collagen-building pathways, with supplier clinical data supporting smoother, firmer-looking skin over time.
Red Algae
Chondrus Crispus
Irish Moss
A red algae whose carrageenans form a hydrating film with antioxidant and photoprotective activity. The cleanser’s signature marine active.
Emollient Oils
Meadowfoam & Apricot Oils
Limnanthes Alba · Prunus Armeniaca
Lightweight emollient carriers that dissolve sunscreen and makeup while leaving skin soft, never stripped.
References
1 Niacinamide & N-Acetyl Glucosamine: Kimball AB, et al. Br J Dermatol. 2010;162(2):435–441. PMID 19845667. · Hakozaki T, et al. Br J Dermatol. 2002;147(1):20–31. PMID 12100180. · Bissett DL, et al. J Cosmet Dermatol. 2007;6(1):20–26. PMID 17348991.
2Bearberry (arbutin): Boo YC. Antioxidants. 2021;10(7):1129. PMID 34356362.
3Galactomyces Ferment Filtrate: Takei K, et al. Clin Exp Dermatol. 2015;40(7):786–793. PMID 25786502. · J Clin Med. 2022;11(16):4645. PMC9409768.
4Ceramide Complex: Spada F, et al. Dermatol Ther. 2021;34(3):e14970. PMC8459234. · Kono et al. J Dermatol. 2021. PMID 34596254.
5Snow Mushroom (Tremella fuciformis): Ma X, et al. Int J Immunopathol Pharmacol. 2021;35. PMC8172338. · Fu H, et al. J Cosmet Dermatol. 2021;20(12):4052–4059. PMID 36757441.
6Fermented Bamboo (Lactobacillus ferment): PMC10520257.
7Panthenol (Pro-Vitamin B5): Ebner F, et al. Am J Clin Dermatol. 2002;3(6):427–433. PMID 12113650.
8GABA: Cosmetics. 2024;11(1):19. doi:10.3390/cosmetics11010019.
9Laminaria (brown seaweed): Murphy MJ, Dow AA. J Clin Aesthet Dermatol. 2021;14(10):37–41. PMC8711622.
10Astaxanthin: Bjørklund G, et al. Molecules. 2022;27(21):7167. PMID 36363994.
11Tocopherol (Vitamin E): Es-Sai B, et al. Molecules. 2025;30(3):653. doi:10.3390/molecules30030653.
12Rosemary (carnosic acid / carnosol): Loussouarn M, et al. Plant Physiol. 2017;175(3):1381–1394. PMID 28916593.
13Rosehip (Rosa canina): Kerasioti E, et al. Antioxidants. 2019;8(4):92. PMC6523071.
14Gluconolactone (PHA): J Cosmet Dermatol. 2023;22(12):3305–3312. doi:10.1111/jocd.15864. · Cutis. 2004;73(2 Suppl):3–13. PMID 15002657.
15Chondrus Crispus (Irish Moss): López-Hortas L, et al. Marine Drugs. 2022;20(11):695. PMC9692426.
16[Peptide Complex]: Croda Beauty. [Peptide Complex] clinical and technical data (supplier data).