Also: Collaxyl / Collaxyl ng (Ashland trade name; water, butylene glycol and hexapeptide-9) · collagen IV and XVII sequence matrikine · not Syn-Coll, which is palmitoyl tripeptide-5
CautionSupplementTopical
Collagen-sequence 'signal' peptide in firming serums; tested in people only as a modified or enhanced version.
#21 of 23 supplements · updated
Onset
Weeks to months, if anything
Lasts
Nothing persists after stopping
Access
Supplement
Cost / month
≈ €4–27
researchers' estimate; no listing to price
Users report
No first-hand Reddit reports name hexapeptide-9 or Collaxyl as the active. It turns up only on ingredient lists of multi-peptide serums (often Indian and Korean 'peptide complex' products) and in lists of what a serum contains, never with an outcome that can be traced to it. The score is a placeholder for 'unknown', in line with how often users of anonymous multi-peptide serums report seeing nothing. Felt nothing: No first-hand reports found, so nothing can be counted.
Best effects
Claimed: firmer skin and softer fine lines via more collagen and a stronger dermal-epidermal junction (supplier and lab data)
Downsides
No identifiable user outcomes · rarely disclosed at a known concentration; one of many peptides in 'complex' serums
Evidence
Small human studies — lab and supplier data say this matrikine, a sequence found in collagens IV and XVII, makes fibroblasts and keratinocytes build matrix. Human data exist only for variants: a 96-person randomised trial of a cyclised version (CHP-9) run by a Chinese cosmetics company, which beat retinol on crow's feet and forehead lines, and an industry study delivering hexapeptide-9 with an ionic-liquid penetration enhancer. Neither tests hexapeptide-9 as sold in ordinary serums
Caveat
Hexapeptide-9 is a hydrophilic six-residue peptide whose sequence occurs in collagens IV and XVII (the basement-membrane and anchoring collagens), and its own penetration into intact skin is poor, as the enhancer study shows. The headline clinical result belongs to a cyclised analogue that does not inherit to Collaxyl. Supplier efficacy numbers are unpublished. No harm signal is known; the uncertainty is about whether it does anything, not about safety.
Typical use
Finished products at supplier-recommended levels (the trade product is a dilute solution of the peptide; brands rarely state how much), once or twice daily.
Getting it
Over-the-counter cosmetic: listed as hexapeptide-9 in multi-peptide serums and firming creams; raw Collaxyl is sold to formulators.
Stacked with
Matrixyl: Usual neighbour in 'collagen peptide' serums; the better-studied of the two. · tretinoin: The proven collagen builder; hexapeptide-9 is at most an add-on.
Safety
Tier by safety barStrict CautionBalanced CautionEvidence only Clean
Seen harmMechanismData gapSilent harmProduct
Seen harm 0/3
No serious adverse events reported in the literature or first-hand; the ingredient has been sold in cosmetics for years, but at small and undisclosed levels inside multi-peptide products, so the zero reflects little traceable exposure as much as reassurance.
No published human safety or efficacy study of hexapeptide-9 as sold. The 96-person RCT tested a cyclised analogue (CHP-9), which does not inherit to the linear peptide beyond showing that a close relative was tolerated at 0.002% for 56 days; the ionic-liquid study pairs it with a penetration enhancer and gives no clinical detail in its abstract. No CIR assessment. Chang et al., J Cosmet Dermatol 2025 (cyclised hexapeptide-9, n=96) ↗
Silent harm 0/3
The only plausible harms are irritation or contact allergy, noticed at once and gone on stopping.
Product 0/3
Bought as finished over-the-counter serums and creams.
Never if
known allergy to a product containing it · pregnancy and breastfeeding (no reproductive data, though systemic exposure from a cosmetic is expected to be negligible)
Each bead is one amino acid in the peptide's chain, coloured by its side chain: grey for non-polar, cyan for polar, blue for positively charged and fuchsia for negatively charged. Length and mix tell related peptides apart at a glance, from a two-residue dipeptide like carnosine to a 43-residue protein like thymosin beta-4. The colours describe chemistry only and predict neither effect nor safety.
non-polarpolarpositivenegative
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. Kept peptides rank by the same reports' mean grade, shrunk the same way, and excluded ones follow in that order.
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 alongside the computed scores until reports arrive.
Safety tier
Each peptide is tiered clean, caution or excluded from its five risk axes under the chosen safety bar. An excluded peptide has a plausible route to serious harm, 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 exclude a peptide. 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.
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.
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.