Also: Procapil (biotinoyl tripeptide-1 + oleanolic acid + apigenin) · biotin-GHK · Capixyl (acetyl tetrapeptide-3 + red clover extract) · RCP serums (Redensyl, Capixyl, Procapil) · The Ordinary Multi-Peptide Serum for Hair Density
SupplementTopical
Cosmetic anti-shedding peptides in cheap leave-on scalp serums; a minority see baby hairs.
Safety tier
Caution
strict bar
Positive
42%
of 25 reports
Per month
≈ €10–20
estimate
Rank
#18
of 23 supplements
At a glance
Access
Supplement
TopicalFelt in 2–6 weeks
15 min1 h6 h1 day1 week1 month
Builds over days or weeks of regular use rather than with each dose.
Best effects
Less shedding · baby hairs at temples, edges and hairline after 2-6 months · hair looks and feels thicker (partly cosmetic coating) · calmer, less itchy scalp for some
Downsides
Scalp itch or irritation · flaking/white residue, sticky or greasy feel · early shed reported by a minority · gains lost within 1-2 months of stopping · headache or palpitations in a few (formula contains caffeine)
Typical use
A few drops to 1 ml leave-on to the scalp once daily (The Ordinary), or a 3-5% Procapil spray once or twice daily; judge after 3-6 months.
Stacked with
Stacked with
Minoxidil: commonly layered at a different time of day; users who credit it most often already use minoxidil or spironolactone · Microneedling: frequently paired; adds its own effect · Ketoconazole shampoo: helps the itch/flaking some get from the serum
Safety
Tier by safety barStrict CautionBalanced CleanEvidence only Clean
Seen harm0 of 3
Mechanism0 of 3
Data gap2 of 3
Silent harm0 of 3
Product0 of 3
Never if
Caffeine sensitivity or arrhythmia, with caffeine-containing serums
Almost all first-hand data is for multi-active serums, chiefly The Ordinary Multi-Peptide Serum (biotinoyl tripeptide-1 and acetyl tetrapeptide-3 alongside Redensyl, Baicapil, AnaGain and caffeine), so no single peptide can be credited. About 40% report real gains: baby hairs at temples and edges or less shedding after 2-6 months, best in shedding (telogen effluvium), traction or post-damage hair. They fade within 1-2 months of stopping. As many see nothing beyond a fluffier, 'plumped' feel, even after a year or two. A minority get itch, flaking on natural hair, or a shed. Two report headaches or palpitations, plausibly from the caffeine in the formula. Felt nothing: ~20% felt nothing; another ~20% mixed (cosmetic thickening only).
I wished I had better pictures but I definitely see an improvement. It looks like I have more baby hairs but actually I think they are my existing hair but just thicker.
PositiveTopical · perimenopausal shedding
Late-40s woman, 10 weeks of The Ordinary Multi-Peptide Serum for Hair Density 3-4 days a week.
Over-the-counter cosmetic: The Ordinary Multi-Peptide Serum for Hair Density (~€20/60 ml), many RCP/Procapil sprays (3-5%) and shampoos, especially in India and Turkey.
No listing can be priced, so the researchers estimate ≈ €10–20 a month.
Cheapest from trusted shops in the EU
Shop
Pack
Price
Per mg
Per month
Testing
Amazon.frEU · FRTrust 3/5Amazon.fr itself is a regulated EU retailer whose A-to-z guarantee covers non-delivery, but the listings used are small third-party marketplace sellers with few or no reviews and no public testing (the AHK-Cu serum is a generic China-made listing), so the actual vendor has only a limited track record.Ships to France for €3.99, 3–5 days.Customs risk low for parcels to France.
serum+5 other actives
€21
—
—
No public tests
Studies
Evidence
Small human studies — industry-run trials of the cosmetic complexes (Capixyl placebo-controlled n=30; RCP vs minoxidil open comparison); no independent trial of biotinoyl tripeptide-1 alone
Caveat
Biotinoyl tripeptide-1 is biotin bound to GHK (without copper); its anti-5-alpha-reductase and anchoring claims come from supplier (Sederma) in-vitro data. Public evidence is two small industry-adjacent trials of blends, and Reddit reports are of blends, so the score is for 'peptide hair serums', not the molecule. Acetyl tetrapeptide-3 (Capixyl) had too few standalone reports for its own entry and is folded in here. No harm path found; the palpitation/headache reports fit the caffeine in The Ordinary's formula and resolved on stopping.
The peptide's chain of amino acids from its start (the N-terminus) to its end, one bead and one letter for each: A alanine, C cysteine, D aspartic acid, E glutamic acid, F phenylalanine, G glycine, H histidine, I isoleucine, K lysine, L leucine, M methionine, N asparagine, P proline, Q glutamine, R arginine, S serine, T threonine, V valine, W tryptophan, Y tyrosine. A modification such as an N-acetyl cap or a C-terminal amide changes how long it lasts in the body. Length tells related peptides apart, from a two-residue dipeptide like carnosine to a 43-residue protein like thymosin beta-4, and predicts neither effect nor safety.
Report grades
Every first-hand Reddit or X report is graded on its own, from glowing through positive, mixed, nothing and negative to bad reaction, and the bar shows how those grades split. Posts that look vendor-adjacent stay on the peptide's page but are left out of the counts.
GlowingPositiveMixedNothingNegativeBad reaction
% positive
The share of a peptide's graded Reddit and X reports that are glowing or positive, vendor-adjacent posts left out. A peptide with few reports is pulled toward the average of all reports, as if it had eight average ones besides its own, so two glowing posts cannot top the list. Peptides rank by this figure, those with no graded report yet after those with one, and Avoid ones after every other entry.
Researcher estimate
No first-hand report of this peptide has been graded yet, so the figure is the researchers' own rating out of 10 from what they read about it. It ranks after every peptide with graded reports until its own arrive.
Safety tier
Each peptide is tiered Clean, Caution or Avoid from its five risk axes under the chosen safety bar. An Avoid peptide carries a real risk of harm, a plausible route to serious harm rather than mere unpleasantness, so it stays listed with the reason but ranks behind every other entry, however good its reviews.
Safety bar
The safety bar sets how much risk it takes to rate a peptide Avoid. Strict: out on any serious mechanism with little human data, or any documented serious harm. Balanced: out on documented serious harm (unless it is obvious, reversible and from a regulated product), or a serious mechanism whose harm would be silent with no human data at all. Evidence only: out only on documented serious harm in humans that is lasting, delayed or from grey-market product.
Seen harm
Documented serious adverse events in humans, from 0 for none despite real exposure to 3 for deaths or several well-documented serious harms. Serious means a hospital or emergency visit or harm lasting weeks, so a headache or a bad night does not count.
Mechanism
A plausible biological route to serious harm at the doses people use, such as growth-factor signalling, hormone-axis suppression, heart or blood-pressure effects or immune activation. It runs from 0 when none is known to 3 when a dangerous pathway has been shown in living animals.
Data gap
How little human safety data exists for the molecule actually sold, from 0 for an approved drug with large trials and years of use to 3 for no human safety data at all. A modified analogue does not inherit its parent's trials.
Silent harm
Whether the feared harm would show quickly or stay hidden, from 0 when it is obvious and goes on stopping to 3 when it is silent and delayed, like tumour promotion or slow organ damage. User reports cannot reveal a harm that takes years to appear, so a high score here limits what good reviews can tell you.
Product
The risk of what people actually buy, from 0 for a regulated pharmacy or supplement product taken by mouth or on the skin to 3 for a grey-market injectable. In one dataset of 6,441 grey-market samples, 42–71% failed basic quality criteria and 15% carried endotoxin; taken by mouth or in the nose, a pack avoids the injection risks.
Evidence
The strongest kind of study behind the peptide's effects, from an approved drug through human controlled trials and small human studies to animal work or nothing of its own. Animal results often fail to carry over to people.
Access
How people get it: as an approved drug, a compounded prescription, an over-the-counter supplement or from the grey market, where nobody checks the vial. The channel decides both the legal position and the risk of a bad batch.
Price per month
Thirty days of the typical dose, from its low end to its high end, priced at the listing a careful buyer would choose: in stock, from a shop scoring 4 of 5 on trust (third-party tested where no score is set), failing that 3, a pure pack before a blend, a European shop first, then the cheapest per mg. The range is the dose's, not the shops'. A per-dose amount counts once a day unless the dose says otherwise. Prices are in euros at ECB rates of 2026-10-29, before shipping; the shop table keeps each listing's price per mg, per gram for bulk supplements. Where no listing can be priced the researchers' own estimate stands in, and says so.
Dose users report
The middle half of the daily doses stated in at least five first-hand reports, vendor posts left out. Where its middle sits more than twice above or below the declared dose, the month is priced at it as well, since what people take is what they pay for.
Shop trust
Each shop's trust on a 1–5 scale, read from its testing and its reputation: 1 for serious red flags (fabricated COAs, scam reports, impersonation, a closed shop), 2 for no public testing, a new shop or active complaints such as seized parcels, 3 for its own COAs or a short track record, 4 for verified third-party testing or a strong reputation, and 5 for third-party batch reports that name the shop, with years of good independent reputation. A shop without a score counts third-party batch testing as 4, its own COAs as 3 and no public tests as 2.
Best value
Within a category or a goal, a peptide that no other beats on both counts: none is rated more positively for the same or a lower monthly price, and none costs less for the same or a higher rating. The chart joins these into the best-value line; the cheapest of them and the best-rated of them both make it, so the line spans the trade-off from cheap to best. Avoid entries never count, and a peptide needs both a % positive and a price to be compared.
Testing
Whether the shop publishes lab results: third-party tested means an independent lab checks each batch, own COA means the shop's own certificate of analysis, and no public tests means neither. A certificate shows purity, not safety.
Added peptide
Some packs sold under one peptide's name hold a second one, such as 5 mg GHK-Cu in a nasal kit, stated only in the description. Sprayed in the nose or injected it reaches the blood like an injection, so it carries the risk of that route and is tiered as the injectable form, whatever its tier on the skin. A pack whose page gives no contents list may hold more than its name.