A 3% peptide serum almost never contains 3% peptide. When a supplier sells a peptide as a ready-made blend, the 3% refers to the blend, and the blend is mostly glycerin and water.1 No federal rule requires any cosmetic label to state a concentration at all, so the number you see is voluntary and undefined.2
No route runs from a label to the real figure. Ingredient lists do yield a ceiling, and recovering it is the useful skill.
Does a 3% peptide serum contain 3% peptide?
Not usually, because the 3% describes a supplier blend instead of a pure peptide. Sederma's technical file for one widely used peptide blend gives its recommended use level as "Dosis recomendada: 3%," and that 3% applies to the whole blend.1
What sits inside the blend changes the arithmetic completely. Sederma prints the composition in this order: Glycerin, Aqua (Water), Butylene Glycol, Carbomer, Polysorbate 20, Palmitoyl Oligopeptide, Palmitoyl Tetrapeptide-7.1 Ingredient lists run in descending order of concentration, so the two peptides are the smallest components of a material that is mostly glycerin and water.2
Three percent of a mostly-water blend puts the peptides somewhere far below three percent of the finished serum. Nobody outside the formulator knows where, because the file gives no individual peptide concentration anywhere.1
What does the 3% on a supplier datasheet refer to?
Supplier percentages describe how much of their material to add to a formula, not how much peptide ends up in it. Laboratory testing in the same file ran at "1%, 3%, 5%" of the blend, not of either peptide separately.1
That detail matters for reading claims. Brands saying their serum matches the concentration used in the studies are describing a blend percentage, and the studies behind it used blend percentages too. Both numbers are internally consistent and neither one tells you the peptide content.
Use levels exist for a practical reason. Formulators buying a peptide as a pre-dispersed blend are buying solubility and stability along with the active, since short peptides are difficult to disperse evenly at tiny weights and a carrier system handles that problem. Suppliers have to say how much of their material produces the effect they tested, and a percentage of their own material is the only form that instruction can take.
Inside the formulation lab the number does its job correctly, and it travels badly outside. Nothing in the supplier's phrasing claims to describe peptide content. Trouble starts when a figure meant for the person mixing the batch appears on the carton for the person buying it.
Where is the peptide in that blend's ingredient order?
Sixth and seventh of seven in the blend's ingredient order. Glycerin, water, butylene glycol, carbomer and polysorbate 20 all come before the two peptides in Sederma's printed order.1
The peptides themselves are named in the file as "Pal-GHK y Pal-GQPR," a three-residue and a four-residue chain.1 Chains that short, present below five other ingredients in a blend added at 3%, end up at a concentration with several zeros after the decimal point. Only the manufacturer holds the exact figure.
Rough arithmetic shows the scale of the dilution without pretending to precision. Add a blend at 3% of a formula and every component of that blend is at most 3% of the formula. Any single component is some fraction of that 3%, and the two peptides are the last two of seven entries in a descending list. Even a generous assumption, where the peptides together take a tenth of the blend, lands them around 0.3% of the finished serum between them.
One caveat matters more than the arithmetic: the tenth is invented. Sederma publishes no split, so every version of this arithmetic rests on an assumption the reader supplies, and the only correct conclusion is the direction: far below 3%, by an amount nobody outside the company can state.1
Does any rule require a percentage on a cosmetic label?
No rule requires a percentage on a cosmetic label. FDA's own labeling guide states the position in a parenthesis, noting that concentrations "need not be declared by regulation."2
Cosmetic ingredient declaration is governed by 21 CFR 701.3. 21 CFR 701.3 requires that a label "bear a declaration of the name of each ingredient" and says nothing at all about quantity.3 A percentage on a cosmetic carton is therefore marketing copy, and a brand choosing to print one is choosing both whether to print it and what it refers to.
Drug products work differently, and that difference is part of why the expectation exists. On a sunscreen or a minoxidil label, a percentage is an active ingredient concentration under a different set of rules. Cosmetic peptides carry no such requirement.
What does the ingredient order actually tell you?
Ingredient order gives you ranking, not amounts. Under 21 CFR 701.3 ingredients must be declared "in descending order of predominance," and FDA's summary repeats it as a plain rule.34
Rank order still tells you something. An ingredient listed third in a nine-item list is present at more than whatever follows it. Sometimes that alone settles whether a hero ingredient is doing real work or decorating a label.
What ranking cannot give you is the size of the gaps. Two ingredients sitting next to each other in a list might be 40% and 38%, or they might be 40% and 0.4%, and the declaration reads identically in both cases.3 Water commonly makes up most of a serum, so the first entry alone can account for more of the bottle than every other entry combined, with the remaining names dividing a small remainder in an order that says nothing about how small.
That is why a peptide's position in a list answers a narrower question than people expect. It tells you which side of other ingredients a peptide falls on. It does not tell you whether the quantity does anything.
Where does the 1% line sit on a label?
On a label the 1% line sits wherever the sub-1% group begins, and below it the ordering rule stops applying. That is where the useful ceiling comes from. Paragraph (f) permits an alternative grouping, listing "Ingredients, other than color additives, present at a concentration greater than 1 percent, in descending order of predominance," followed by "Ingredients, other than color additives, present at a concentration of not more than 1 percent, without respect to order of predominance."3
FDA's summary states the same thing from the reader's side: "ingredients present at one percent or less (21 CFR 701.3(f)(2)) may be declared without regard for predominance."4
One class of ingredient marks where that line falls on a real label. Preservatives, fragrance and color additives almost always sit under 1%, so the first of those in a list marks roughly where the sub-1% group begins. Anything after it is 1% or less. That is a ceiling and not a number, and a ceiling answers the question that matters most often: whether an ingredient is present in a meaningful quantity or a trace.
One caution on reading it that way. Nothing requires a brand to use the grouped format, so a label in strict descending order throughout gives no 1% landmark at all.3
What can hide behind the word fragrance?
Fragrance can stand in for a list of its own, and 21 CFR 701.3 permits it explicitly. Every ingredient must be declared "in descending order of predominance, except that fragrance or flavor may be listed as fragrance or flavor."3
One entry reading fragrance may therefore represent dozens of individual materials, declared as one word in one position. One limit applies: an ingredient qualifies only if it is a fragrance "within the meaning of such term as commonly understood by consumers," so the provision cannot be used to bury an active.3 Components serving two purposes have to be declared for each function they perform unless they are named outright.3
For somebody reading a peptide serum's list, the practical effect is a gap of unknown width near the bottom. Fragrance usually sits in the sub-1% group, so its presence rarely changes what you can infer about a peptide's ceiling. It does mean the list you are reading is shorter than the formula it describes.
Why do two supplier documents list the same blend differently?
Supplier documents use different formats and sometimes different ingredient names, and neither format is the one that appears on a finished label. Sederma's file prints the blend in descending order, so it conveys concentration ranking.1 Croda's own datasheet for the same blend prints it as "Butylene Glycol (and) Carbomer (and) Glycerin (and) Palmitoyl Tetrapeptide-7 (and) Palmitoyl Tripeptide-1 (and) Polysorbate 20 (and) Aqua," which is alphabetical and conveys no concentration information whatsoever.5
Peptide names also differ between the two documents. Sederma's file says Palmitoyl Oligopeptide and the parent company's datasheet says Palmitoyl Tripeptide-1, for the same peptide.15 Palmitoyl Oligopeptide is a superseded INCI name, so anybody matching a product label against an older supplier document can conclude the ingredients differ when they do not.
Access limits the comparison further. Most fields on that datasheet, including the chemical composition and compliance details, are marked "Visible After Login."5
What happens to a blend's name on a finished label?
A blend's name disappears from a finished label, because FDA requires the components to be listed individually. The labeling guide instructs that for proprietary mixtures, "The compounds of such mixtures must be separated, the '(and)' omitted."2
A serum built on a 3% addition of a seven-component blend therefore shows those seven components scattered through its ingredient list in their own positions, with no indication that they arrived together or in what proportion. A trade name appearing in marketing copy will not appear in the ingredient declaration at all. That removes the last route to reconstructing the blend percentage from the label.
A separated list also makes a blend's carrier indistinguishable from the formula's own. Glycerin arriving inside a peptide blend and glycerin added separately for humectancy appear as one entry, combined, in whatever position their total earns.2 A reader seeing glycerin high in a list cannot tell which part of it came along with the active.
All of this runs in the brand's favor without anybody breaking a rule. Marketing copy can name a blend and quote its use level, the ingredient list can show the components, and the two cannot be reconciled against each other by anyone outside the lab. Both statements are accurate and the combination is unverifiable.
Can a brand leave an ingredient off the list entirely?
Yes, with FDA's acceptance. 21 CFR 701.3(a) allows that where an ingredient is "accepted by the Food and Drug Administration as exempt from public disclosure," then "in lieu of label declaration of identity the phrase 'and other ingredients' may be used at the end of the ingredient declaration."3
FDA's guide describes the same provision and notes that a product whose confidentiality request is still under review "may not bear the label statement."2 Seeing "and other ingredients" on a label therefore tells you an exemption was granted and tells you nothing about what was exempted.
FDA has to accept the claim first, so the provision runs through a formal process, and that process is a meaningful limit on it. Paragraph (a) points to 720.8(a), so a company cannot simply decide an ingredient is secret and omit it; FDA has to accept the claim, and until it does the phrase cannot appear.3 A label carrying it has been through that review.
What the phrase costs a reader is position as well as identity. An exempted ingredient sits at the end of the declaration regardless of how much of it is present, so the ordering information for that entry disappears along with its name.3 In practice the provision is used rarely and for genuine formulation secrets, and the point for reading a label is narrow: a list ending that way is incomplete by design and by permission.
Did the 2022 cosmetics law change any of this?
No, not for what a label has to tell you. The Modernization of Cosmetics Regulation Act of 2022 gave FDA substantial new authority, and none of it requires a concentration on a carton.6
What the law added runs toward the regulator instead of the shopper. Manufacturers and processors "must register their facilities with FDA and renew their registration every two years," a responsible person has to list each marketed product with FDA "including product ingredients" with annual updates, records supporting safety substantiation have to be kept, and serious adverse events must be reported "within 15 business days."6
Taken together, those requirements make the asymmetry the point. FDA now receives product ingredient information under the listing requirement, and a consumer reading the same product's label gets the same declaration they got before 2022, with no quantities on it.6
One labeling change is pending and it concerns something else. FDA is required to establish "Fragrance allergen labeling requirements," with no detail yet on what they will demand, and nothing in that mandate addresses ingredient concentrations.6
What does a real ingredient list look like worked through?
Worked through, a label gives you a ranking and one boundary, and the exercise is short enough to do in a store.
A plausible serum lists water, glycerin, butylene glycol, niacinamide, carbomer, polysorbate 20, phenoxyethanol, palmitoyl tripeptide-1, palmitoyl tetrapeptide-7, fragrance. Phenoxyethanol is a preservative, and preservatives sit under 1% in ordinary use, so the sub-1% group plausibly starts there. Both peptides appear after it. Each one is therefore 1% or less, and the regulation stops ordering them against each other at that point, so their order carries no further information.3
The first six entries tell you something different. Water, glycerin, butylene glycol, carbomer and polysorbate 20 are exactly the carrier components of the peptide blend described above, appearing separately because FDA requires proprietary mixtures to be broken apart on the label.12 Their presence high in the list is consistent with a blend added at a few percent, and it is equally consistent with those ingredients having been added on their own for texture. A label cannot distinguish the two cases.
The best available read of that list is a sentence and not a number: the peptides are present, each at 1% or less, and the serum's marketing percentage refers to something the list does not define. Anybody offering a tighter figure from the same list is estimating.
How is this different from peptide purity?
Purity and concentration answer different questions, and conflating them is the most common error on this topic. A 99% purity figure describes a raw material, meaning the powder is 99% the intended peptide and 1% other things. The second figure describes a finished product, meaning how much of that powder sits in what you apply.
Both numbers can be true at once and they constrain each other not at all. A serum can contain a 99% pure peptide at a concentration of 0.002% and both figures are accurate. A supplier certificate reporting purity says nothing about the serum, and a serum percentage says nothing about what was in the drum.
The two numbers also move for unrelated reasons. Purity is a property of a synthesis and a purification run, set before the material ships, and improving it means better chromatography. Formulators set concentration by cost, solubility, stability and skin tolerance, and raising it means more expensive material in every bottle. A brand can buy the purest grade available and still formulate at a trace level, and the purity figure is the one it will quote.
Conflating them is useful to whoever does it, and the usefulness is why the error persists. A high purity number reads like a high strength number to anybody not watching the units, and it is the number a supplier hands over freely.
Purity is one of four numbers that get quoted around peptide products, and each of the four answers a different question.
| Number you see | What it refers to | What it does not tell you |
|---|---|---|
| Supplier use level, such as 3% | How much of the supplier's blend goes into a formula1 | How much peptide is in the blend, or in the finished product1 |
| A percentage in marketing or on a carton | Whatever the brand chooses it to mean, since no rule defines it23 | Anything a reader can verify |
| Raw-material purity, such as 99% | How much of a shipped powder is the intended peptide | How much of that powder is in the bottle |
| Position in the ingredient list | Rank against the other ingredients34 | The size of the gaps, or any order below the 1% line3 |
Only the fourth row comes from the product you are holding. The first two come from documents you cannot see, and the third describes a drum in a warehouse.
What would let you work out a real concentration?
Three disclosures would settle it, and brands are not required to make any of them. The blend's addition rate in the formula, the peptide's concentration inside the blend, and confirmation of which blend was used would together give a figure.
Formulators hold all three and customers hold none. Independent testing of a finished product can measure peptide content directly, and it is the only route that does not depend on disclosure. No routine consumer-facing version of that testing exists for cosmetic peptides.
A certificate of analysis does not close the gap either, and it gets offered as though it does. Certificates describe a raw material lot: identity, purity, water content, sometimes heavy metals. A certificate for a peptide powder is a document about the powder, generated before anybody decided how much of it to put in a bottle, so a brand supplying one has answered a question about its supplier and not about its product.
Testing a finished serum is a different exercise and a harder one. The peptide has to be extracted from an emulsion or a gel and quantified against a reference standard, usually by liquid chromatography. That work requires the reference peptide, a validated method for that matrix and a laboratory willing to run it. That work is routine for pharmaceutical release testing and rare for cosmetics, and nobody is obliged to commission it.
What has not been measured?
Four limits sit outside what any label can tell you.
Individual peptide concentration inside a commercial blend is not published by the supplier whose file was read for this guide.1 Finished-product peptide content is not required on any label and not independently reported.2 Whether a stated percentage refers to a blend or to a peptide is left to each brand, with no definition enforced. Skin penetration at whatever the real concentration turns out to be is a separate question again, since a concentration in a bottle is not a dose at a target. Palmitoylated peptides carry a fatty tail specifically to help them cross the stratum corneum, and how much crosses at a trace concentration is a measurement nobody publishes per product.
How well a peptide holds up over a product's life sits outside all of it too. Whatever gets measured at filling is not what sits in a bottle opened eight months later, and no cosmetic label reports either figure.
Common questions
Does a 3% peptide serum contain 3% peptide?
Not usually, because the 3% refers to a supplier blend. Sederma's technical file for a widely used peptide blend gives its recommended use level as "Dosis recomendada: 3%," applying to the blend, whose own composition is mostly glycerin and water.1
Is a cosmetic brand required to state ingredient percentages?
No federal rule requires it, and 21 CFR 701.3 asks for ingredient names without any quantity.3 FDA's labeling guide states that concentrations "need not be declared by regulation."2
What order are cosmetic ingredients listed in?
Most abundant first, in descending order of predominance under 21 CFR 701.3. FDA's summary states that "The ingredients must be declared in descending order of predominance."4
Where does the 1% rule come in?
Under 21 CFR 701.3(f)(2), ingredients "present at a concentration of not more than 1 percent" may be listed "without respect to order of predominance."3 Anything after the sub-1% group begins is therefore 1% or less.
How do you find the 1% line on a label?
Preservatives, fragrance and color additives almost always sit under 1%, so the first of those in a list marks roughly where the group begins. Nothing in 21 CFR 701.3 requires a brand to use the grouped format, so some labels give no landmark at all.3
Does the ingredient list tell you how much of something is in a product?
Ranking only, since 21 CFR 701.3 requires no numbers alongside the names.3 An ingredient listed above another is present at a higher concentration. Below the 1% line even that ranking stops applying.24
Why does the same peptide appear under different names?
INCI names change over time, and Palmitoyl Oligopeptide is a superseded name for palmitoyl tripeptide-1. Sederma's file prints the older name where the parent company's datasheet prints the current one, for the same peptide.15
What does "and other ingredients" mean on a label?
Under 21 CFR 701.3(a), where an ingredient is "accepted by the Food and Drug Administration as exempt from public disclosure," that phrase "may be used at the end of the ingredient declaration."3 It confirms an exemption was granted and identifies nothing.
Will a peptide blend's trade name appear in the ingredient list?
No, because the Food and Drug Administration requires a proprietary mixture's components to be listed individually. Its guide instructs that "The compounds of such mixtures must be separated, the '(and)' omitted," so the blend name does not appear.2
Is 99% purity the same as 99% concentration?
Different measurements entirely, and a serum can hold a 99% pure peptide at a concentration near zero with both figures accurate. Purity describes a raw material and concentration describes a finished product.
What percentage did the studies on these blends use?
Blend percentages, with the Sederma file reporting its laboratory testing at "1%, 3%, 5%" of the blend.1 Neither peptide was tested at those levels on its own. A brand matching the study concentration is matching a blend percentage.1
How many ingredients come before the peptides in that blend?
Five ingredients precede them in the file's printed order: Glycerin, Aqua (Water), Butylene Glycol, Carbomer and Polysorbate 20.1
Can you calculate the peptide concentration from a label?
No route exists from a label alone, because 21 CFR 701.3 requires no quantities.3 Someone would need the blend's addition rate, the peptide content inside the blend, and confirmation of which blend was used. No rule requires a brand to publish any of them.2
Does a higher percentage mean a better product?
A percentage with no stated referent cannot support that comparison, and 21 CFR 701.3 defines neither figure.3 Two serums both labeled 3% may refer to different blends at entirely different peptide contents.
Do drug labels work the same way?
Drug labeling is a separate framework under which active ingredient concentrations are required, unlike cosmetic declaration under 21 CFR 701.3.3 That contrast is part of why a percentage on a cosmetic carries an expectation it cannot meet.
What can the word fragrance hide on an ingredient list?
Fragrance may represent many individual materials declared as a single entry, because 21 CFR 701.3 allows ingredients to be declared in descending order "except that fragrance or flavor may be listed as fragrance or flavor."3 An ingredient qualifies only if it is a fragrance as commonly understood by consumers, so the exception cannot be used to bury an active.3
Did MoCRA change cosmetic ingredient labeling?
Not for concentrations, and the 2022 law left label content alone. The Modernization of Cosmetics Regulation Act of 2022 added facility registration, product listing with FDA "including product ingredients," safety substantiation records and adverse event reporting, and it requires no concentration on a label.6
Does a certificate of analysis tell you a serum's strength?
No certificate of analysis answers that question, because 21 CFR 701.3 governs the label and a certificate describes a raw material lot. Certificates cover identity, purity and water content, and they are generated before anybody decides how much of the material goes into a bottle.
What would actually tell you a serum's peptide content?
Independent laboratory testing of a finished serum measures peptide content directly, with no dependence on a Sederma or Croda datasheet. No routine consumer-facing version of that testing exists for cosmetic peptides.
Sources
- Sederma ("Sederma - miembro del Grupo Internacional Croda"), MATRIXYL 3000 technical file, in Spanish. Read at source via a chemical distributor's hosted copy of the manufacturer's document. The file gives the recommended use level, the composition order, the two peptide shorthand names and the blend percentages used in testing. It states no individual peptide concentration anywhere, and that absence is the central fact this guide rests on. It prints the peptide as Palmitoyl Oligopeptide, a superseded INCI name. ↩1 ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13 ↩14 ↩15 ↩16 ↩17 ↩18 ↩19
- 21 CFR 701.3, Designation of ingredients. Read at source from the Code of Federal Regulations PDF on govinfo.gov, 2015 annual edition. Because it is the 2015 compilation and not the live eCFR text, the current wording should be confirmed against eCFR before republication. The live eCFR page refused automated access from this environment, so it was not read. ↩1 ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13 ↩14 ↩15 ↩16 ↩17 ↩18 ↩19 ↩20 ↩21 ↩22 ↩23 ↩24 ↩25
- Croda, Matrixyl 3000 technical datasheet, accessed through a business-to-business materials database. Read at source, partially gated. The chemical composition, origin, benefits detail, compliance and availability fields are marked "Visible After Login" and were not read. The INCI string and the supplier-stated functions were visible. ↩1 ↩2 ↩3 ↩4
- US Food and Drug Administration, "Modernization of Cosmetics Regulation Act of 2022 (MoCRA)." Read at source on fda.gov. Source for the facility registration, product listing, safety substantiation and adverse event reporting requirements, and for the pending fragrance allergen labeling mandate. The page does not mention ingredient concentration disclosure at all, and it gives no enactment date, naming the law and linking the enrolled bill H.R. 2617. ↩1 ↩2 ↩3 ↩4 ↩5