Tier 1
Adenosine
Adenosine appears at exactly 0.04% in eight of twelve Youlief products. That number is not a coincidence - here is what it means.
Beauty Science · Knowledge
Ingredient Library
These pages cover the ingredients used across the Vegalab and Youlief ranges - what each one is, the level it is typically used at, and what the evidence supports at that level. Concentration matters more in cosmetics than almost any other factor, and an ingredient present at a trace is not the same claim as the same ingredient at a studied level.
Several entries are group pages rather than single ingredients, because the useful content is the comparison. The vitamin C forms differ in stability and in what has actually been tested; the humectants differ in molecular weight and in what they do without an occlusive over them. A page per molecule would repeat itself and bury the comparison that answers the question.
Where the evidence is thin, the page says so rather than filling the gap with supplier material. Some of these ingredients have decades of independent clinical work behind them; others have a single in-vitro study and a lot of marketing. Both situations are described plainly, with study type and funding labelled.
Claims stay cosmetic throughout, describing appearance rather than physiological structures, and findings are attributed to the researchers who produced them.
Each page carries the level the ingredient is actually used at in the range, where that is known, alongside the level the studies used. Those two numbers are frequently different, and a page that gives you only the second is not telling you much about the product in front of you.
Where an ingredient also appears in the crop range, it is covered in full once and linked from the other pillar rather than written twice. Rosemary oil is a pesticidal active in crop science and a fragrance and antimicrobial component in skincare - one molecule, two genuinely different use cases, and one page that states which is which.
Pages in this section
Group
AHAs: mandelic and lactic acid
Alpha hydroxy acids differ mainly by molecular size, and size determines how fast they work and how much they sting.
Tier 1
Alpha-arbutin
A hydroquinone glycoside that inhibits tyrosinase without hydroquinone's regulatory and safety baggage.
Group
Antioxidants: resveratrol, ferulic acid, tocopherol and carnosine
Antioxidants work as a network, not as individuals - which is why they are combined, and why the level matters more than the name.
Group
B vitamins: folic acid and cyanocobalamin
Two essential vitamins with clear systemic roles and much thinner topical rationales. An honest look at both.
Tier 1
Bakuchiol
Bakuchiol is marketed as a gentler retinol alternative. What it shares with retinoids, what it does not, and how strong the comparison really is.
Tier 1
Beta-glucan
A polysaccharide with genuine immunomodulatory activity - and a molecular weight that makes topical delivery the central question.
Tier 1
Biotin (vitamin B7)
Genuinely essential for keratin production, genuinely useful in deficiency, and genuinely unsupported for hair growth in people who are not deficient.
Group
Black soybean and beer yeast
Two 20% inclusions anchoring the density line. Substantial levels, traditional use, and a modest evidence base.
Group
Botanical extracts in the range
Twenty-plus botanical extracts appear across the two ranges. What each is claimed to contribute, and how to tell a standardised extract from a label i
Tier 1
Caffeine
Real vasoconstrictive and phosphodiesterase-inhibiting activity, a legitimate use for periorbital puffiness, and a much weaker case for everything els
Group
Centella asiatica and the cica triterpenes
Madecassoside, asiaticoside, asiatic acid and madecassic acid are the four markers behind every cica product. What they do, and what the concentration
Group
Ceramides and the barrier lipid triad
Ceramides, cholesterol and free fatty acids in roughly equimolar proportion are what the stratum corneum is actually made of. Ratio matters more than
Group
Collagen: topical versus oral
Nine collagen forms appear across the range. Topical collagen cannot become your collagen - but that is not the same as saying it does nothing.
Group
Contour actives: arginine, L-carnitine and artichoke
The three-part contour complex, examined honestly. Each ingredient has a real mechanism; the question is whether topical application reaches the tissu
Flagship
Delivery systems compared
Liposomes, multi-layer biopolymer capsules, cyclodextrins and microneedles all solve different parts of the same problem. What each actually does.
Tier 1
Ectoin
An extremolyte from salt-loving bacteria that works by organising water rather than by binding it. Distinctive, well-evidenced, and barely covered in
Tier 1
Ergothioneine
An amino acid antioxidant that cells actively transport rather than passively absorb - which makes it unusual, and unusually interesting.
Group
Ferments and biotech ingredients
Seven ferment ingredients across the range. Fermentation genuinely changes what an ingredient contains - but the term covers everything from well-char
Group
Fragrance allergens: limonene and linalool
Two of the twenty-six fragrance substances the EU requires to be declared. What that declaration means - and what it does not.
Tier 1
Glutathione
The most oversold brightening ingredient in the category. What the evidence supports for topical, oral and intravenous use - which are three very diff
Tier 1
Green tea and catechins
One of the best-evidenced botanical antioxidants, at an unusually high inclusion in this range - and a stability problem worth understanding.
Group
Humectants compared
Glycerin, betaine, trehalose, sodium PCA and the rest all hold water - but they behave differently in dry air, and one of them is quietly the best-evi
Flagship
Hyaluronic acid: the molecular-weight question
Eight hyaluronic acid forms appear across the range. What the penetration research actually shows about molecular weight - and why a long HA ingredien
Group
Licorice actives
Glycyrrhiza-derived actives with genuine anti-inflammatory and pigmentation activity - and, in this range, levels that require an honest note.
Group
Marine and algae extracts
Ten marine ingredients across the range, from well-characterised polysaccharides to extracts identified only by species.
Tier 1
Melatonin in skincare
Better known as a sleep hormone, but a capable antioxidant with a legitimate topical rationale - and some claims that outrun the evidence.
Tier 1
NAD+ (nicotinamide adenine dinucleotide)
NAD+ is a 663-dalton, water-loving, unstable molecule, which makes topical delivery genuinely difficult. What the research shows - including 2025 evid
Flagship
Niacinamide (vitamin B3)
Niacinamide at 2%, 5% and 15% - what changes with concentration, why the vitamin C warning is largely a myth, and where tolerance limits sit.
Group
Sodium PCA and the natural moisturising factor
Skin makes its own humectant system. Sodium PCA and free amino acids are attempts to top it up rather than to add something foreign.
Tier 1
Panthenol (pro-vitamin B5)
One of the few genuinely uncontroversial actives: humectant, barrier support and soothing, with a real conversion mechanism and almost no downside.
Group
Peptides in skincare, decoded
Twelve differently named peptides appear across the range. The naming is impenetrable, the mechanisms are real, and the concentrations are the part no
Flagship
Retinoids: retinal, retinol and the rest
Retinal, retinol, retinyl esters and tretinoin differ by how many conversion steps they need. What that means for strength, irritation and formulation
Tier 1
Salicylic acid (BHA)
Oil-soluble, keratolytic, and the only common exfoliant that gets into a pore. Why solubility is the whole point.
Tier 1
Silk proteins: fibroin and sericin
Two proteins from the same cocoon with different jobs. Fibroin is the structural fibre, sericin the glue that holds it - and sericin is the more inter
Group
Soothing actives: bisabolol and allantoin
Two of the most widely used comfort ingredients in cosmetics, with real mechanisms and a claims vocabulary that has to stay careful.
Tier 1
Squalane
The saturated version of a lipid your own skin makes. Stable, non-comedogenic, and one of the least controversial emollients available.
Tier 1
Tranexamic acid
A plasmin inhibitor repurposed for pigmentation. How it differs from tyrosinase inhibitors, and why 5% topical is a meaningful number.
Group
UV filters in the Youlief sunscreens
Seven filters across three sunscreens, all modern photostable organics. What each covers, and why the combinations look the way they do.
Group
Vitamin C forms compared
L-ascorbic acid, ascorbyl glucoside and 3-O-ethyl ascorbic acid are not interchangeable. Stability, conversion and evidence all differ.
40 pages in this section.
Product claims, registrations and availability vary by jurisdiction. Always read and follow the applicable product label.
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