The Ordinary's Multi-Peptide Serum for Hair Density is a peptide serum: Caffeine, Biotinoyl Tripeptide-1, Acetyl Tetrapeptide-3, and the trademark complexes REDENSYL, Procapil, CAPIXYL, BAICAPIL, in a lightweight leave-in for thicker, fuller, denser-looking hair. Tara's Follicle-Stimulating Scalp Serum is a peptide serum too — the same class of actives. The difference is what we put around the peptides.
Does a multi-peptide serum actually work?
Within limits, yes — and the peptide doing the heavy lifting is acetyl tetrapeptide-3 paired with biochanin A (the CAPIXYL complex, in The Ordinary's bottle and in ours). Biochanin A independently inhibits scalp type-2 5-alpha-reductase — the follicle enzyme that converts testosterone into the DHT behind pattern thinning. That mechanism paper has been cited 230 times in the scientific literature.1 And in a 24-week independent, triple-blind trial, an acetyl-tetrapeptide-3 + biochanin A combination held level with 3% minoxidil on terminal hair count (+8.3% vs +8.7%, no significant difference).2 Peptides are real. They are also modest — and the in-vivo density numbers on the trademark complexes are supplier-funded, in The Ordinary's serum and every other. We say so.
The dose decides — a label is not a dose
Here is the factor almost every comparison skips: a peptide on the INCI list tells you it's present, not that there's enough of it for the trial data to apply. CAPIXYL's clinical data was generated at its working level — the supplier's specified range is 3–5% of the finished formula. Below 3%, citing that study is overreach. Most product pages name the complex and stop; the dose stays unstated.
Tara's claims are dose-gated. Every claim on this page passed a dose check before it shipped: if the active weren't at its studied working level, the claim would not exist — not on this page, not on the bottle. And the gate cuts both ways: onion's famous regrowth figure came from crude juice at orders of magnitude above any serum dose, so we don't claim it; hydrolyzed keratin's fibre reinforcement washes out over shampoo cycles, so we tell you to reapply with each wash. That is what dose honesty looks like when it costs us something.
Tara's isn't bare peptides — here's the rest of the bottle
A peptide-only serum gives you the peptides and stops. Tara's Follicle-Stimulating Scalp Serum carries the peptides and then keeps going:
- Onion extract (Allium cepa) — a flavonoid-rich scalp botanical; its quercetin raised perifollicular microcirculation in an in-vivo model.3 (An organosulphur/flavonoid scalp botanical — not the crude onion-juice regrowth claim; see below.)
- Soy protein — strengthens the hair fibre and supports thickness and density.
- Inositol (Vitamin B8) — supports the hair root and helps reduce shedding.
- Hydrolyzed RNA & DNA fractions — nucleotide fractions that support scalp cellular vitality.
- Hydrolyzed keratin — cortex-penetrating keratin peptides raised fibre break-stress ~18.6%, so the hair you have resists breakage.4
Same peptide science as the serum you were comparing — then onion, soy protein, B8, nucleotides and keratin on top. One bottle, a fuller formula.
The Ordinary Multi-Peptide Serum vs. Tara Follicle-Stimulating Scalp Serum
| The Ordinary Multi-Peptide Serum | Tara Follicle-Stimulating Scalp Serum | |
|---|---|---|
| Peptides | Caffeine, Biotinoyl Tripeptide-1, Acetyl Tetrapeptide-3, REDENSYL, Procapil, CAPIXYL, BAICAPIL | Acetyl Tetrapeptide-3 + Biochanin A (CAPIXYL) |
| Independent 5-alpha-reductase mechanism | Supplier in-vivo | Biochanin A, cited 230×1 |
| Peptide RCT vs minoxidil | Supplier in-vivo | Level with 3% minoxidil, n=322 |
| Beyond the peptides | Caffeine + plant extracts | Onion extract, soy protein, inositol (B8), RNA/DNA fractions, hydrolyzed keratin |
| States the working dose | Complexes listed; dose levels not stated on the product page | Dose-gated claims — CAPIXYL clinical range is 3–5%; no claim ships below the studied level |
| Discloses supplier funding | Rarely | Yes, on the page |
| Format | Lightweight leave-in, once daily | Lightweight leave-in, once daily |
How to use it
Massage a few drops into a clean, dry scalp once daily, ideally at night. It is a lightweight leave-in — don't rinse it out. Density moves over months, not days: this is a nightly habit, not a one-week fix.
What it does NOT do
It is not a drug, and we won't dress it up as one. The peptide density gains are real but modest, and the strongest peptide numbers are manufacturer-funded. The onion here is a scalp botanical — the famous "87% regrowth" onion figure comes from crude onion juice on alopecia areata, an autoimmune condition, and does not transfer to a cosmetic-dose extract. This serum is not a treatment for alopecia areata, androgenetic alopecia, or any diagnosed condition. If your shedding is sudden, patchy, or fast, that is a different problem — see a specialist.
So which should you buy?
Want bare peptides at the lowest price? Buy the cheapest one — the complexes are the same. Want the peptides plus onion, soy protein, B8, nucleotides and keratin in one scalp serum — with the mechanism disclosed honestly? That is the one we make.
Citations
1. Hiipakka RA, et al. Structure-activity relationships for inhibition of human 5-alpha-reductases by polyphenols. Biochem Pharmacol 2002;63(6):1165-1176. PMID 11931850. (Cited 230 times, Scopus.)
2. Lueangarun S, Panchaprateep R. An herbal extract combination (biochanin A, acetyl tetrapeptide-3, ginseng) versus 3% minoxidil for androgenetic alopecia: a 24-week, randomised, triple-blind, controlled trial. J Clin Aesthet Dermatol 2020;13(10):32-37. PMID 33584955.
3. Effect of quercetin on hair regeneration and perifollicular microvasculature (HIF-1alpha, in-vivo model). PMID 37285263. (Cited 34 times, Scopus.)
4. Hydrolyzed keratin penetration and fibre break-stress (~18.6%, ex vivo, manufacturer-funded). PMID 33037625.
Every ingredient claim above is graded, with its study, in the evidence table.