The cleansing product with peptides is a rinse-off cosmetic formula containing one or more peptide ingredients. However, its primary function remains cleansing the skin, which helps remove excess sebum, impurities, residues of cosmetics, and other substances found on its surface.
Whether the peptide component provides an additional, measurable effect is a separate scientific question.
One cannot answer these questions based solely on the presence of a peptide in the product composition. What matters are the identity of the specific peptide, the entire formulation of the cosmetic product, its stability, the way the product is applied, the amount of substance remaining on the skin after rinsing, and – above all – the type of claimed effect.
Rinsing causes cleansing products containing peptides to differ scientifically from products that remain on the skin, such as peptide serum creams. The concentration of the peptide in the packaging does not necessarily correspond to the amount remaining on the skin after washing. Similarly, the detection of a specific substance on the skin surface after rinsing does not mean that the intact peptide has reached the living tissue.
At the same time, the short time of contact with the skin does not justify the opposite assumption that every peptide or other functional ingredient present in the rinsed formula must be ineffective.
Evidence is found between these two extremes.
Researchers can analyze the effectiveness of cleansing, the product's tolerance, the accumulation of substances on the skin after rinsing, penetration, and clinical effects. However, each of these questions requires an appropriate research method.
In this article, we explain how to interpret such evidence and how studies of other types of cosmetics can provide useful scientific context without being a direct confirmation of the efficacy of a specific peptide-based cleansing product.
How peptides are used in cleansing products
The presence of the peptide does not define the entire product
Peptides consist of amino acid residues linked by peptide bonds. In cosmetics, this term can refer to various materials, including specific short sequences of amino acids, chemically modified peptides, and mixtures of smaller fragments formed by the breakdown of larger proteins.
These materials are not interchangeable.
They can differ in molecular size, electrical charge, solubility, chemical stability, and analytical methods needed to identify and quantify them.
The word „peptide” therefore describes a broad chemical category, not a single standardized active ingredient in cosmetics.
The cleansing product also contains many ingredients responsible for cleansing itself, formulation properties, and the user experience during use. Depending on the product, these may include surfactants, solvents, humectants, viscosity regulators, and other auxiliary ingredients.
They affect the way the product is distributed, the formation of foam, its interaction with sebum and cosmetic residues, its ease of rinsing, and the feel of the skin after washing.
Therefore, abundant foam, easy rinsing, slipping, or the softness of the skin after application cannot be automatically attributed to the peptide just because it is particularly highlighted on the label.
The most useful scientific description should refer to a complete intervention: a ready-made cleansing product, the method of its use, and the additional effect that is suggested to occur.
The statement „this cleansing product contains a peptide” describes the composition.
Whereas the statement „this product reduces wrinkles thanks to this peptide” is a claim regarding the causal relationship and effectiveness.
The second statement requires much stronger evidence.
Cleansing products based on amino acids are not automatically peptide products
The terms „amino acid” and „peptide” are biochemically related, but they do not describe the same substance.
The surfactant obtained using an amino acid can be produced from the amino acid as a starting material, but this does not mean that it is equivalent to the amino acid chain of the peptide under study as a cosmetic peptide.
Similarly, a protein extract or protein hydrolysate should not be automatically considered an equivalent of a specific synthetic peptide.
The hydrolysate may contain numerous peptide fragments of varying length and composition. The individual fragments may have different physicochemical and biological properties.
Therefore, evidence regarding a precisely characterized peptide sequence cannot be extrapolated to every component whose name contains words such as „protein”, „amino acid” or „hydrolyzed”.
This distinction helps to avoid a significant error in the interpretation of the evidence: the assumption that similar biochemical terminology means the presence of the same scientifically tested substance.
First, the identity of the author must be established. Only then can it be assessed whether a particular scientific publication actually refers to the material in question.
Laboratory analysis confirms the composition, not the effectiveness
Laboratory analyses can determine whether a specific peptide is present in a cosmetic product, and, using appropriate methods, also estimate its amount that can be recovered from the formulation.
Studies on developing LC-MS/MS methods for palmitoylated peptides in cosmetic products show that the identity and content of the peptide can be determined analytically, rather than being inferred solely from the marketing language.[1]
Such evidence is valuable, but its significance remains limited to a specific question.
Confirmation of the presence of the peptide in the cleansing product does not prove that the product provides a clinical benefit.
The individual experiments answer different questions.
The content analysis determines what is contained in the packaging. The deposition study after rinsing checks what remains attached to the skin after washing. The penetration study assesses where the substance can be detected in specific layers of the skin. The controlled clinical study, on the other hand, verifies whether the finished product changes a specific result.
These types of evidence can complement each other, but one does not automatically replace the other.
Stability is another matter entirely.
The peptide should remain properly characterized in the finished product for a significant period of its storage. We discuss this issue in more detail in the article about Storage of peptides.
Evidence that the same peptide remains stable in a simple laboratory solution does not mean that it will behave identically in a surfactant-rich product with a different pH, packaging, preservative system, and other formulation components.
What was studied directly in cleansing products
Direct studies of cleansing products containing peptides are more reliable than the transmission of results obtained for products left on the skin.
In one randomized, double-blind study, 60 people with mild to moderate acne participated. For eight weeks, the cleansing product containing 5-aminolevulinic acid and peptides was compared with the basic cleansing product. [2]
The publication described a reduction in the number of changes compared to the initial value in the group using the complex product, as well as better assessments by researchers and greater satisfaction among participants compared to the control group.[2]
The study is directly related to the topic discussed, because the tested intervention was actually a cleansing product.
However, the interpretation still requires a clear definition of the boundaries.
The product contained a combination of 5-aminolevulinic acid and peptides. Therefore, the experiment did not allow the influence of the peptides themselves to be isolated as the sole explanation for the observed results.
The abstract also does not specify what amount of intact peptide remained on the skin after rinsing, nor what part of it, if any, reached the specific area of the skin.
Most importantly, a positive result regarding this specific compound cannot be generalized to all products marketed as peptide-based cleansing products.
The study justifies further evaluation of the specific tested formula.
However, it does not establish a therapeutic effect for the entire category of products.
Contact time and rinsing
An exhibition is more than just a time measured by a clock
Contact time is important when evaluating rinse-off cosmetics, but exposure cannot be reduced solely to the number of seconds the product remains on the face.
During washing, the formula simultaneously interacts with water, the skin, sebum, residual cosmetics, and other substances that are removed.
The product can be diluted after application. It can be moved during application or massage. The individual ingredients can interact with the skin or the material on its surface before the entire mixture is rinsed off.
This process is fundamentally different from applying a specific amount of serum and leaving it on the skin.
Therefore, in the case of claims regarding the delivery of the component, researchers must characterize the actual exposure conditions.
The amount of product used, the degree of dilution, the contact time, the method of application, the method of rinsing, and the moment of taking the sample can all be important factors.
A laboratory experiment that uses prolonged exposure cannot be automatically presented as a representation of regular facial washing.
There is also no scientifically established universal minimum contact time after which each product cleansing with peptides becomes effective.
Different peptides, formulation bases, and claimed effects require separate verification.
Extensions of the washing time beyond the method of use specified for a given product should not therefore be considered to be a method based on evidence for transforming the washed product into an equivalent serum that remains on the skin.
Deposition, penetration and biological activity are different phenomena
Deposition, penetration, and biological activity describe different levels of evidence.
Deposition means that a certain amount of the substance remains on the surface of the skin or in a specific superficial area after the product is applied and removed.
Penetration refers to the movement of substances into specific layers of the skin.
The biological effect goes even further. It requires evidence linking the appropriate exposure with a specific reaction or result.
| Question | Evidence that can answer them | Which he himself does not confirm in himself |
|---|---|---|
| Is the peptide present in the cleansing product? | Verifiable analysis of identity and content | Staying on the skin after washing |
| Does it remain after rinsing? | Standardized study of recovery or deposition after flushing | Delivery to living tissue |
| Does the intact peptide reach the target layer? | Analysis of individual layers of the skin | Obvious or clinical effect |
| Does the product improve a specific outcome? | Controlled study of the finished product | Individual contribution of the peptide |
| Does the peptide provide an additional effect compared to the base? | Appropriately selected comparison of matched formulations | Equivalentities of other products |
Separating these questions does not reduce the value of the evidence.
However, it allows each result to correspond exactly to the question it was intended to answer, without expanding it into much broader claims.
The deposit after flushing can be measured, but analogies have limitations
The deposition of the substance after rinsing can be investigated experimentally.
Studies concerning salicylic acid in rinse formulations have, for example, developed methods for quantifying deposition on human and swine skin.[3]
Salicylic acid is not a peptide.
The amounts retained on the skin in this study, therefore, cannot be presented as an indicator of peptide retention.
The significance of this study is methodological.
It shows that the question „what remains on the skin after washing?” can be investigated directly, instead of answering it based on assumptions.
An analogous peptide study would require an analytical method validated for the specific peptide, the formulation of the cleansing product, and the biological material being studied.
Among other things, the recovery efficiency, the interference caused by other components of the formulation, the analytical background, and the detection limits should be taken into account.
This is also important for interpreting negative results.
The failure to detect the peptide after rinsing does not necessarily mean that absolutely no molecule of the peptide remains on the skin. The amount may simply have fallen below the detection limit or the limit of quantification of the method used.
The reverse situation is equally important.
The detection of a very small amount of peptide does not automatically mean that the appropriate amount of it has reached the skin site needed to produce the claimed effect.
Analytical detectability and clinical significance are related, but are not the same thing.
Studies of the penetration of products remaining on the skin cannot be presented as studies of products that are flushed down the toilet.
Studies of formulations remaining on the skin can help in understanding the principles of peptide delivery, but they should not be presented as direct evidence regarding cleansing products.
In an in vitro study of acetyl hexapeptide-8 in emulsion, it was found that most of the recovered material remained on the surface, a small amount was recovered in the outer layers of the skin, and no peptide was detected in the skin proper and the receptor fluid under the tested conditions.[4]
The experiment involved prolonged exposure, followed by analytical purification.
This was not a clinical study of a facial cleansing product containing peptides.
Its significance lies in showing why the location where the peptide was recovered is important.
The study does not allow for a universal absorption percentage for rinse-off products to be determined.
It also does not prove that every peptide behaves the same way as acetyl hexapeptide-8.
Similarly, if one formulation left on the skin delivers a peptide differently from the other, this does not mean that the cleansing product will replicate any of these exposure profiles.
Purification effects versus peptide-specific effects
The product can effectively cleanse without a proven peptide mechanism.
A cleansing product containing peptides can be an effective cosmetic product without demonstrating a specific biological mechanism resulting from the presence of the peptide.
The finished product can, for example, effectively remove cosmetic residues, be well-spread, easily rinsed off, and provide users with satisfying sensations during use.
These are legitimate product characteristics if they are properly measured.
However, they do not constitute evidence of collagen synthesis, deep penetration of the peptide, or changes in cellular signaling simply because the cosmetic product contains a peptide.
The study should therefore clearly specify what result was measured.
The removal of standardized cosmetic residues tests the effectiveness of cleansing.
Instrumental humidity measurement evaluates skin properties related to water content under specific test conditions.
The participants' questionnaires measure their subjective experiences.
Each of these results can provide useful information.
However, they should not be combined into an imprecise statement that the product simply „works”.
The claim regarding the action of the peptide itself requires an additional level of evidence, as researchers must distinguish its effect from that of the other components of the cleansing formula.
Comparing two different products can reveal differences in their performance as finished formulations.
However, it usually does not allow determining which specific component is responsible for this difference.
Moisturizing and comfort are not the same thing as structural skin reconstruction
The skin may appear softer or more comfortable after washing due to the properties of the entire formulation and the immediate condition of its surface.
This can be a significant cosmetic effect.
However, it does not independently promote the formation of new collagen in the epidermis or the long-term remodeling of its structure.
Similarly, a slight feeling of tightness after washing can be valuable information regarding user comfort, but it is not a direct measure of the structure of deeper tissues.
Researchers can use both subjective and instrumental measurements, provided that the results remain clearly separated.
The consistency of the various types of measurements can strengthen the conclusion that the finished product performs its function well.
However, Nadal does not automatically support the proposed molecular mechanism.
The measurement time also matters.
The observation conducted directly after washing answers a different question from the result obtained after several weeks of regular use.
Both also differ from the result measured after discontinuing use of the product.
If the declared effect is to be sustained, observation is necessary even after the product is discontinued.
Natural skin peptides are not evidence of the delivery of peptides from cosmetics
Searching for scientific publications can lead to studies seemingly related to the topic, which in reality concern a completely different peptide-related issue.
In one study of human forearm skin, the effect of commonly used cleansing products on the naturally occurring antimicrobial peptide LL-37 and bacterial parameters was analyzed after washing.[5]
This was a study concerning the skin's own biological defense system.
It did not prove that the cleansing product delivers an externally added cosmetic peptide.
This distinction is of great importance during the selection of studies.
A publication containing both the terms „peptide” and „cleansing product” may refer to endogenous skin peptides, a cleansing product used solely as part of a larger protocol, or to a completely different research question.
Therefore, search results require scientific selection before they can be used to justify a claim about the product.
The same principle applies to the terminology related to the microbiome.
The measurement of bacteria, the measurement of endogenous peptide, and the acne result are separate endpoints.
None of them should be automatically presented as a universal measure of „skin health” without explaining what exactly was being assessed.
More information about distinguishing between different types of evidence in the case of reactive and acne skin can be found in the article about peptides for sensitive and acne-prone skin.
Multistage care does not allow the cleansing product’s action to be isolated.
If participants simultaneously start using a cleansing product, serum, moisturizing cream, and sunscreen, the observed improvement should initially be attributed to the entire treatment regimen being tested.
The study can still provide valuable information.
However, it does not allow the cleansing product to be cited as the cause of the effect if the study design does not separate its contribution from the action of the other cosmetics.
This is particularly important when the product’s website refers to a study of the entire skincare system as evidence of the effectiveness of a single cosmetic product.
It is important to determine whether the cleansing product differed between the comparison groups, while the other important care elements remained similar.
If several products were changed at the same time, assigning the entire result to the cleaning stage is not justified.
The same restriction applies to uncontrolled „before and after” observations reported by individual users.
Such reports can describe what a person noticed, but alternative explanations remain other cosmetics, expectations, seasonal changes, environmental conditions, and the natural variability of the skin condition.
What should the test of a cleansing product show
The comparison should correspond to the claimed statement
The research project should be based on a specific claim that needs to be evaluated.
The claim regarding the effectiveness of the purification process requires an appropriate comparator product and a clearly defined endpoint related to the removal of impurities.
The assessment of tolerance requires appropriate examination of symptoms, reactions, and adverse effects.
The claim that the peptide itself provides an additional benefit should be best tested by comparing the same or very similar base formula with the peptide and without it, while maintaining control over the remaining important differences.
The study of a face cream containing palmitoylated pentapeptide, in which a tailored base formulation was used, provides an example of such an approach to attributing the effect to a specific component.[6]
In the context discussed, however, it remains an example of a research project.
It does not prove that a washed-off product containing the same or another peptide will reproduce the results obtained for a cream left on the skin.
The type of comparison should also be clearly presented when communicating the results.
An improvement over the initial value does not automatically mean that the product was more effective than the control.
Similarly, the statement that there was a statistically significant change in one group and no change in the other does not in itself mean that the difference between the groups was statistically significant.
It is necessary to directly analyze the appropriate comparison between the groups.
The study should replicate the method of use and measure the appropriate exposure.
A well-designed study of a cleansing product should describe the conditions of its use in sufficient detail to allow the exposure being studied to be understood.
This also applies to the important details of application and rinsing.
If the main claim concerns the deposit of the peptide after rinsing, researchers should measure it under realistic washing conditions, rather than infer retention based on the product's composition alone.
If the claim concerns the delivery of an intact peptide, the analytical method should, as far as possible, distinguish the original molecule from fragments, metabolites, or other signals.
The importance of taking a sample also has significance.
Detecting the substance on the surface of the skin should not be presented as evidence that the peptide has reached the true skin.
Even convincing evidence regarding the delivery of the substance does not automatically mean visible or clinically significant benefit.
A separate study of the effects would be needed, which would combine the exposure with the declared effect.
At the same time, not every simple claim regarding cleansing requires advanced tissue penetration studies.
The level of evidence required should correspond to the scale of the claim.
Demonstrating the effective removal of surface contaminants is a much simpler scientific question than determining that a peptide present in the rinsed product reaches living tissue and causes a specific biological change.
Checking measurement errors and reporting uncertainties
Well-designed product studies try to limit the possible sources of errors that can be avoided.
Randomization can help evenly distribute the differences between the participants.
A biased assessment, when possible, can limit the impact of expectations.
Standardized photographs, controlled environmental conditions, and repeatable measurement locations can improve the comparability of results.
None of these elements guarantees the correctness of the research conclusions.
Together, however, they make it easier to interpret them.
The report should also include information on the sample size, individuals who discontinued participation, significant baseline differences, and the simultaneous use of other cosmetics.
The magnitude of the effect and the confidence intervals help to understand both the magnitude of the observed difference and the associated uncertainty.
For comparison, a marketing statement that lacks information about the comparison group, the measurement method, or the moment of evaluation is difficult to interpret scientifically.
In the same analysis, tolerance must be taken into account.
The product cannot be reliably described as „not causing irritation in everyone” just because a small study reported few adverse reactions.
The characteristics of the studied population, the number of participants, and the reasons for the resignations all influence how widely the results regarding tolerance can be generalized.
It is necessary to clearly indicate what remains unexplained
The direct evidence regarding cleansing products containing peptides identified in the studies discussed is much narrower than the broad commercial category of such cosmetics.
Current evidence does not confirm that every product that cleanses with peptides leaves clinically significant amounts of intact peptide after rinsing.
They also do not show that the entire category provides anti-aging effects or other biological effects typical of peptides.
This is the limit of available evidence, not proof that every cleansing product containing peptides is ineffective.
A specific formula can still provide valuable cleansing properties or sensory effects that improve skin comfort.
Some individual formulations may also merit further study in terms of additional effects.
What is most important is that stronger claims regarding the activity of peptides require correspondingly stronger evidence obtained for the actual finished product under conditions similar to the intended method of use.
Frequently asked questions
Can serum tests confirm the effectiveness of a cleansing product?
Serum studies can provide valuable scientific context, but they do not directly confirm the efficacy of the product being rinsed off. Serum and cleansing products differ in their formulation, dilution ratio, contact time, and whether the product remains on the skin or is removed with water. Formulation studies also show that the delivery of peptides may depend on the surrounding system.[7] The presence of the same peptide in serum and cleansing product does not therefore mean equivalent exposure or efficacy. Evidence regarding the cleansing product should refer to its own finished formulation, application conditions, and claimed efficacy. In the case of products remaining on the skin, a separate issue is also the method of application. peptide serum and the interpretation of more complex ones multipeptide serum.
Do the peptide cleansing products remain on the skin after use?
This is possible, but no retention of the peptide after rinsing can be assumed for any formulation. Determining the amount remaining on the skin requires a validated analytical method that allows the measurement of a specific molecule after realistic washing and rinsing. Studies on the deposition after rinsing of non-peptide substances show that such a question can be investigated experimentally, but they do not provide a percentage value for peptide retention. [3] In the case of a product that has not been tested in this way, the amount, integrity, and location of the remaining peptide remain uncertain.
Is the amino acid-based cleansing product the same as the peptide product?
No. The cleansing ingredient derived from an amino acid is not automatically equivalent to a specific peptide sequence, and neither of them should automatically be identified with protein hydrolysate. These terms can refer to chemically different materials that perform different functions in cosmetics. Therefore, evidence regarding a specific peptide cannot be transferred to another product simply because its composition uses similar biochemical terminology. The first step is to determine the actual identity of the ingredient.
Does abundant foam mean that the peptides are working?
No. The foam results primarily from the properties of the surfactants and the entire formulation system, and is not a measure of peptide activity. Abundant foam may affect user experience and preferences during use, but does not confirm peptide penetration or biological response. The claim regarding the peptide would require a separate study with a conclusion appropriate to such a claim. Even very effective removal of surface contaminants does not in itself allow a determination whether the peptide provides additional biological benefit.
Can a peptide-based cleansing product treat acne?
Such a conclusion cannot be applied to the entire category of products that purify with peptides. One controlled study concerned a specific compound containing peptides and 5-aminolevulinic acid, used by people with mild or moderate acne. [2] The results refer to this specific intervention and population. Since the formula contained several important ingredients, the study did not allow the peptides to be identified as the cause of the observed effects. Therefore, it cannot confirm the effects of other cleansing products or prove that the addition of a peptide alone transforms the product into a therapeutic product.
Does longer washing ensure better delivery of peptides?
No. Extending the contact time does not prove that a greater amount of intact peptide reaches the appropriate skin layer or that a clinical effect will occur. Delivery depends on the specific peptide, formulation, skin environment, and conditions of use. Formulation studies show that the vehicle can influence peptide transport. [7] Therefore, prolonged laboratory experiments with a product left on the skin cannot be used as justification for extending the time of use of a cleansing product beyond the method intended for the given formulation.
Does the concentration of the peptide in the package correspond to the amount absorbed by the skin?
No. The amount contained in the packaging, the amount remaining after rinsing, and the amount reaching the specific layer of skin are three different measurements. Analysis of the cosmetic product can determine the content of the peptide in the formulation, but it does not show what happens to it after diluting the product, applying it to the skin, and rinsing it off.[1] A separate study is needed to assess exposure after application. Therefore, a high or highly marketed concentration of the peptide does not in itself indicate absorption, clinical efficacy, or superiority over another formulation.
Does the softness of the skin after washing mean collagen production?
No. The softness or comfort of the skin after cleansing are sensory effects and do not directly measure collagen synthesis. The entire formulation can alter sensations on the skin’s surface through many mechanisms without causing deeper structural remodeling. Therefore, studies should separate the participants’ sensations, hydration measurements, and endpoints regarding tissues. If after applying the product the skin appears softer, that is the result that can be reported. A conclusion regarding collagen would require separate evidence to study this specific process.
Are all peptides completely removed during flushing?
Such a statement is too broad. Retentivity after rinsing may depend on the component, the formulation matrix, the skin surface, the method of washing, and the sensitivity of the analytical method. Studies of rinsed formulations show that residues of substances can be detected after washing, although the cited study concerned salicylic acid and not a peptide. [3] Analytical methods also have certain detection limits. Therefore, the absence of a peptide does not necessarily indicate a complete absence of the molecule, and the detection of a small amount does not clinically demonstrate significant retention.
Can a skin laboratory test prove a visible cosmetic effect?
No. Laboratory experiments can investigate the penetration, deposition, or retention of a molecule under controlled conditions, but they do not replace clinical studies assessing the actual effects. For example, the study of acetyl hexapeptide in vitro provided information on where the peptide could be recovered under specific experimental conditions. [4] However, it did not demonstrate a discernible cosmetic benefit in people using the cleansing product. Therefore, laboratory results should remain linked to the model used, while effects seen, long-term results, and tolerability should be evaluated in appropriately designed human studies.
Do the results regarding the skin microbiome indicate the delivery of added peptides?
No. The study of a cleansing product may concern the population of bacteria or naturally occurring skin peptides, without at all investigating the delivery of an external cosmetic peptide. The LL-37 study, for example, concerned the endogenous antimicrobial component belonging to the skin defense system.[5] It did not show that the commercial product delivered an added peptide. Therefore, when interpreting microbiome and peptide studies, it is necessary to clearly specify the source of the measured molecule.
Does the study involving the cleansing product and serum confirm the effectiveness of the cleansing product itself?
Usually not. If participants simultaneously start using several products, the observed result applies primarily to the entire treatment regimen being studied. The study may still be valuable, but isolating the effect of the cleansing product requires a design in which this element differs between groups, while the other relevant factors are controlled. Without such separation, attributing all the improvement to the cleansing product is not justified.
Does the term „clinically tested” mean proven peptide activity?
No. The wording „clinically tested” does not inform about what exactly was tested, what endpoint was evaluated, whether a comparator group was used, or what the result was obtained. A clinical assessment may concern tolerance, cleansing efficacy, hydration, participants’ satisfaction, or other properties, without examining the individual effects of the peptide. A more valuable description indicates who participated in the study, what product was used, for how long, what was measured, and whether the result differed from the corresponding control.
Are peptide-based cleansing products automatically suitable for sensitive skin?
No. Tolerance depends on the entire formulation and individual skin characteristics, not just the presence of one category of ingredients. A product with peptides may also contain surfactants, preservatives, fragrance substances, plant ingredients, and other compounds that are relevant for tolerance. Small studies conducted in selected groups do not represent all types of sensitive or reactive skin. The mere presence of a peptide cannot therefore guarantee the product’s mildness.
Can the „before and after” photos confirm the effectiveness of the cleansing product?
Photographs can document skin appearance, but in themselves they are not sufficient to demonstrate a causal relationship. Differences in lighting, camera position, facial expressions, concurrent skincare, environmental conditions, and the natural variability of skin can affect comparisons. Standardized photographs become more valuable when they are combined with clearly defined endpoints, consistent shooting conditions, blinded evaluation, and an appropriate comparison group.
Does a higher number of peptides mean a better cleansing product?
No. The number of peptide names in the composition does not inform about their stability, retention after rinsing, delivery to the skin, or the effect in the clinical setting. Analytical confirmation of the presence of several peptides would only answer part of the question. [1] Their behavior still depends on the entire formulation and the conditions of use. Therefore, a multi-peptide product requires proper comparison at the level of the finished formulation if it is to be presented as more effective.
What evidence would justify the claim regarding the specific action of the peptide in the cleansing product?
The strongest evidence would combine a well-characterized finished product with a controlled result corresponding to the claimed benefit, and when the claim depends on the delivery of the peptide – also with appropriate measurements conducted under realistic rinsing conditions. Comparing the product with a very similar base formulation without the peptide would help determine whether the peptide adds something beyond the action of the other ingredients. The population, study duration, comparator group, and endpoint should correspond to the stated claim. Until such relationships are demonstrated, broader claims regarding the peptide mechanism remain hypotheses rather than confirmed effects of the finished product.
Applications
Cleansing products containing peptides should primarily be evaluated as complete rinse-off formulas, rather than as peptide preparations that remain on the skin placed simply in a different packaging.
Their primary function is purification, and this property can be directly investigated. Additional claims regarding peptides introduce separate scientific questions.
The peptide content, the stability of the formulation, the retention after rinsing, skin penetration, and clinical effects represent different levels of evidence. The demonstration of one does not automatically confirm the next.
The analysis can, for example, confirm the presence of a specific peptide in the product.[1] However, it does not show what amount remains on the skin after washing. Detection of the substance after rinsing may indicate some degree of retention, but it does not necessarily indicate penetration into living tissue. On the other hand, demonstrating penetration does not automatically constitute evidence of a visible or clinically significant benefit.
There are direct studies on the complex cleansing product containing peptides. [2] They are important because the cleansing product was actually the intervention being studied, not a serum or cream. However, they concerned a specific complex formulation and do not establish the universal efficacy of all cosmetics marketed as cleansing products containing peptides.
Studies of other ingredients used in rinse formulations can also help to understand how to measure deposition after washing.[3] Meanwhile, experiments with peptides in products remaining on the skin provide context regarding the formulation-dependent delivery of the substance and the importance of the site where the molecule is detected.[4][7]
These studies provide a scientific context.
However, they should not be used as evidence that any peptide-based cleansing product leaves a significant amount of intact peptide on the skin or replicates the effects observed with products left on the skin.
It is particularly important to distinguish between the action of the entire product and attributing the effect to a specific peptide.
The product can effectively remove impurities, keep the skin in a comfortable condition, support its hydration under certain study conditions, or obtain good participant ratings. All of these results can be justified and useful.
However, none of them independently proves that a peptide is responsible for it.
Determining the individual contribution of a peptide usually requires a study design that allows the effect of the peptide to be separated from the effect of the remaining part of the formulation.
The most valuable evidence therefore describes the specific cleansing product, the identity of the peptide, if relevant for the question under investigation, the comparative product, the application and rinsing conditions, the population studied, the measurement method, the moment of evaluation, and the result.
If such data are lacking, the uncertainty should remain visible, rather than being replaced by assumptions that result solely from the presence of the word „peptide”.
In a practical interpretation of the evidence, neither extreme is justified. It would be a too far-reaching conclusion to assume that every peptide found in every cleansing product is completely ineffective just because the product is rinsed off. It is equally poorly justified to assume that the mere presence of a peptide makes such a product equivalent to a peptide-based cosmetic product left on the skin.
The correct conclusion depends on what has actually been measured for a specific finished product.
Disclaimer
The article is purely educational and scientifically informative in nature. It discusses cleansing products containing peptides, the science of cosmetic formulations, the exposure associated with rinse-off products, and methods for interpreting evidence regarding skin care. It is not intended to diagnose or treat skin diseases, nor to provide individual advice regarding skin care, recommendations for acne treatment, or a recommendation for a specific cleansing product, peptide ingredient, or commercial product.
Results of studies involving a single peptide, cleansing product, or complex formulation should not be automatically extrapolated to the efficacy of another product. Differences in peptide identity, concentration, formulation, surfactant system, stability, contact time, rinsing conditions, and other components may influence the significance of published results.
Similarly, evidence from laboratory models, deposition studies, or formulations remaining on the skin do not automatically indicate equivalent exposure or the same effects when the product is used as intended.
Tolerance also depends on the entire product and the individual characteristics of the user. The presence of a peptide does not guarantee that a cleansing product will be suitable for every person or every type of skin.
Individuals with persistent acne, significant irritation, chronic skin disease, or other dermatological problems should, if necessary, seek an individual assessment by a suitably qualified specialist, rather than relying solely on general information about cosmetics.
References
- Chirita, R. I., Chaimbault, P., Archambault, J. C., Robert, I., & Elfakir, C. (2009). Development of a LC-MS/MS method to monitor palmitoyl peptides content in anti-wrinkle cosmetics. Analytica Chimica Acta, 641(1-2), 95–100. https://doi.org/10.1016/j.aca.2009.03.015
- Lee, H. J., Kim, J. Y., Park, K. D., & Lee, W. J. (2020). Randomized controlled double-blind study of a cleanser composed of 5-aminolevulinic acid and peptides on mild and moderate acne vulgaris. Journal of Cosmetic Dermatology, 19(7), 1745–1750. https://doi.org/10.1111/jocd.13232
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