Oral products containing peptides and advertised as „plumping” usually aim to make the lips look fuller, smoother, more supple or more defined. However, the term „lip plumping” can describe several very different effects. A cosmetic product can increase hydration, smooth fine lines resulting from dryness, add a greater shine, temporarily change the impression of fullness, or affect a specific, measurable lip dimension. None of these effects in themselves prove a lasting increase in the volume of the lip tissue.
The presence of a peptide in the composition also does not automatically indicate which mechanism is responsible for the observed improvement. A peptide product may simultaneously contain hyaluronic acid, emollients, film-forming substances, plant ingredients, and compounds that elicit sensory sensations or a short-lasting effect of fuller lips. Therefore, before attributing the effect to a single identified ingredient, the entire finished formulation must be evaluated.
Clinical studies related to the cosmetic effect of fuller lips include, among others, multi-ingredient products containing peptides, topical formulations containing hyaluronic acid, and lip plumper products that do not contain peptides. In these studies, various measurement methods and observation periods were used. Some evaluated hydration, others the specific dimension of the lips, while others used visual scales of fullness, three-dimensional imaging, or participants’ satisfaction ratings.
Therefore, evidence becomes much easier to interpret when moisture, perceived fullness, objectively measured dimensions, and volume assessed using three-dimensional methods are treated as separate results, rather than being combined into a single broad concept of „lip augmentation”.
What exactly do the declarations regarding fuller lips mean?
One term can describe several different effects
The expression „fuller lips” sounds unambiguous, but from a scientific point of view it can refer to very different measurements.
In one study, fuller lips may mean that participants or researchers assessed them visually as more prominent. In another study, researchers may notice an improvement on a standardized photographic scale. Another study may measure one linear dimension using a slider, while another may estimate changes in the three-dimensional geometry of the lip surface.
These results may be linked, but they are not equivalent.
Therefore, the product declaration should clearly indicate what has actually been measured.
For example, a glossy cosmetic can change the way light reflects off the surface of the lips, affecting the visual impression of their fullness. A moisturizing product can reduce the appearance of dryness and fine lines, making the lips appear smoother and fuller. However, some ingredients can cause short-term local reactions that may include redness or visible fullness.
The proposed biological mechanism of action of the peptide is another matter altogether.
Several such effects may occur simultaneously after the use of one product; however, in order to determine which process is responsible for the observed change, appropriate measurements and a proper comparator group are needed.
For the same reason, an impressive „before and after” photo or a clear sensation of tingling are not sufficient evidence of the action of a specific peptide. None of these observations identifies the component responsible for the change, does not confirm the mechanism of action, or shows whether the effect will persist.
The cosmetic effect of fuller lips is not the same as permanent augmentation
Temporary cosmetic improvement can still be an important result.
A product for the lips does not need to cause permanent anatomical changes to yield a noticeable cosmetic result. However, the duration of the effect should be described precisely.
If the lips appear fuller when using the product regularly, this means that the effect was observed during the period of use. This does not automatically mean that the change will remain after discontinuing use of the product.
This distinction is particularly important when local cosmetics are referred to by terms such as „lip filler”.
Local cosmetics called „lip fillers” are not automatically equivalent to injected fillers.
Local and injectable products differ in the route of administration, formulation, tissue exposure, concentration, mechanism of action, and the time of effect. Even if both contain a component with the same general name, such as hyaluronic acid, they should not be considered equivalent interventions.
We discuss more about the properties of hyaluronic acid in cosmetic formulations in the article. Peptides and hyaluronic acid.
To demonstrate the equivalence of the local cosmetic treatment and the injection procedure, a properly designed study directly comparing the two interventions would be needed, with clearly defined endpoints and sufficient observation time.
The mere statement by a participant that they prefer a local product does not prove that it provides the same degree of volume increase, the same duration of action, or the same biological effect as a preparation administered by injection.
The peptide is only one of the components of the finished formulation
Many peptide-based lip products are complex formulations.
In addition to peptides, they may contain hyaluronic acid, emollients, humectants, plant extracts, film-forming substances, pigments, flavor and fragrance components, and substances that produce a short-lasting sensation or fuller-mouth effect.
This causes a significant problem with assigning the action to a specific component.
If the finished product improves hydration, smoothness, or perceived mouthfeel, this observation primarily applies to the entire formulation. Without proper comparative testing of the individual ingredients, a result cannot be automatically attributed to a peptide.
This problem is particularly significant in the case of formulations containing many different peptides and active ingredients. We discuss it in more detail in the article. Multipeptide serum.
In an earlier clinical study, two-step oral care containing a tripeptide complex along with growth factors, hyaluronic acid, emollients, and a separate plumper formulation were evaluated.[1]
The study provides information regarding the entire care regimen.
However, it does not prove that the tripeptide itself was responsible for all the observed changes.
The same principle should be applied when interpreting modern multi-ingredient masks, balms, lipsticks, overnight products, or lip tints. The inclusion of a single peptide on the packaging does not mean that the other ingredients lose their scientific significance.
Moistening and temporary changes in the appearance of the lips
The skin of the mouth should be examined directly
The visible part of the mouth has characteristics that differ from the typical skin of the face.
In a biophysical study involving 303 women, the lips were compared with the skin of the cheeks. In the winter conditions used during the study, greater water loss and lower surface moisture values were observed on the lips. [2]
This provides a useful biological context that helps to understand why hydration can be particularly important for the appearance and comfort of the mouth.
It also shows why the results obtained for normal facial skin should not be automatically applied to the lips.
This study did not, however, cover peptidic products for the mouth.
It does not prove that every balm corrects barrier dysfunction or that peptides are needed to improve oral hydration.
It describes the properties of a specific anatomical area.
Evidence regarding oral biology and evidence confirming the effectiveness of a specific cosmetic product are related to each other, but they address different questions.
Moisture can change the texture and visibility of fine lines
Dry-looking lips can appear rough, cracked, scaly and less uniform.
Increasing hydration can smooth the surface and reduce the visibility of fine lines and peeling. These are real cosmetic effects.
However, they should not be automatically presented as evidence of the formation of new collagen, new adipose tissue, or permanent anatomical enlargement of the lips.
In a four-week open-label, two-step study with hyaluronic acid for the lips, 36 women participated. Clinical signs, moisture measurements, and one dimension measured with a digital caliper were evaluated. [3]
The beneficial observations provide information about what happened during the use of this particular regimen.
However, since the preparation contained many ingredients and no comparison was used to isolate their individual effects, it is not possible to determine which ingredient was responsible for the individual effects.
The study also does not confirm a permanent increase in the size of the mouth.
If the authors of the study use the term „long-lasting effect,” it should be interpreted within the limits of the actual observation period. Several weeks of observation cannot be taken as an assertion of unlimited durability.
Moisture, redness, shine and fullness are different effects
The product can increase the moisture content of the lips without measurably increasing their size.
It may increase the visible redness without improving hydration.
A shiny surface can make the lips appear more voluminous without causing a measurable increase in the three-dimensional volume of the tissues.
These effects can occur simultaneously, but they should not be combined into an inaccurate claim that the product simply „enlarges” the lips.
In a study involving 60 women, the product Lip Plumper based on ginger was evaluated. The observed effect depended partly on the measurement method used. Profilometry detected a short-term change that was not detected by simpler anthropometric measurements.[4]
This was not a peptide study.
Its significance lies in showing how strongly conclusions regarding the „plumping” effect can depend on the endpoint, the measurement method, and the length of observation period.
The sensations during use do not indicate the mechanism of action
Tinging, a feeling of warmth or cold are often associated with cosmetics intended to give a fuller-looking mouth.
Such sensations do not indicate the action of peptides.
In a small open-label study, a product containing capsaicin, cinnamon, and menthol was evaluated. Short-term changes in the assessed mouth-filling sensation and sensory effects were noted.[5]
These components do not constitute evidence of the activity of the peptides.
The study shows, however, that non-peptide ingredients can cause pronounced sensations in products advertised as mouth-enlarging.
The absence of baking does not therefore automatically mean a lack of effectiveness.
Similarly, stronger tingling does not automatically mean a better effect.
Sensory sensations and the cosmetic effect should be evaluated separately.
This is especially important because the irritation itself can temporarily increase redness or swelling, causing a change in appearance that should not be automatically considered a desirable cosmetic effect.
How to measure the volume of the mouth?
The photo shows the appearance, but it does not automatically measure the volume.
„Before and after” photos can be useful if the conditions of the photography are exactly standardized.
The lighting, the distance of the camera, the head position, the facial expressions, and the presence of any cosmetic residue should be as similar as possible.
However, a simple photograph does not directly calculate the three-dimensional volume of the mouth.
Their arrangement is particularly important.
Contraction of the lips, slight opening of the mouth, a change in the tension of the facial muscles, or another degree of relaxation can noticeably change their apparent shape.
The sheen and color also affect the reflection of light and can enhance the impression of fullness.
This does not mean that photography is useless.
It, however, shows why its standardization is necessary.
A well-designed study should indicate whether the photographs were evaluated by blinded observers, whether makeup and product residues were controlled, and whether the same anatomical area was analyzed during each visit.
The scale measures the specific dimension, not the total volume of the mouth.
A digital caliper measures a specified linear distance or thickness.
It can therefore provide useful quantitative data.
However, increases in one measured dimension should not be automatically described as equivalent increases in the total three-dimensional volume of the object.
In an earlier study of combined therapy, lower lip measurement was used in conjunction with corneometry and clinical assessment [1].
Each method answered a different question.
Corneometry provided information about the water content. The caliper measured a specific dimension. The clinical assessment concerned the visible appearance.
Simply describing the measurement result as „an increase in mouth volume” without indicating the actually measured parameter can therefore overly broaden the significance of the results.
Similarly, the percentage change in one linear dimension cannot be automatically converted into an identical percentage increase in the total volume of the container.
Validated scales of completeness standardize the visual assessment
The photonumeric scale uses reference images and previously defined levels, allowing observers to more consistently assess the apparent full range of the mouth.
Validation studies can verify whether different observers attribute similar results and whether the differences between the levels are clinically noticeable.
Validation studies of the full-mouth scale showed that the method can provide reproducible clinical assessment [6].
Another methodological study analyzed the assessment of mouth volume or thickness and its relationship with three-dimensional measurements.[7]
These studies are important because they improve the way fullness of the mouth is measured.
However, they do not constitute proof of the action of a specific peptide cosmetic.
Validation of the measurement method and confirmation of the product's effectiveness are two different scientific issues.
An improvement of one degree on the full scale indicates a change in the assessment of appearance according to the given scale.
It cannot be automatically converted into a specific number of milliliters of additional tissue or a specific percentage increase in anatomical volume.
3D imaging also requires careful interpretation
3D imaging can provide more detailed information about the geometry of surfaces than ordinary photography.
Depending on the system used, researchers can estimate changes in a specific area of the mouth and compare surface characteristics at subsequent time points.
The quality of the results depends on the methodology, however.
The study should describe the calibration, image matching, the method of determining the examined area, the repeatability of measurements, and whether the observed difference exceeds the expected measurement variability.
Even a very precise imaging system in itself does not indicate the cause of the change.
The measured geometric difference may, depending on the situation, result from moisture, the product layer on the surface, transient swelling, natural variability, or other intervention.
An appropriate comparison group therefore remains essential.
Three-dimensional measurement is more useful than an unstandardized visual impression when the question concerns geometry.
However, it does not automatically confirm the formation of new collagen, the specific biological activity of the peptide, or the permanent growth of tissue.
Different measurements should not be treated as equivalent.
Humidity measurements primarily provide information about the water-related properties of surface materials. They are not a direct measure of the new volume of tissue.
The texture or scaly appearance assessment describes the visible condition of the oral surface. It is not a direct evidence of collagen production.
The verified full scale standardizes the visual assessment of appearance. It is not automatically equivalent to measuring volume in milliliters.
The gauge measures a specific linear dimension and should not be treated as a direct measurement of the total three-dimensional volume.
3D imaging provides information about the geometry of a specific area, but without proper control it does not explain why the geometry has changed.
Satisfaction questionnaires provide valuable information about perceived benefits and product acceptance, but they do not replace objective measurements.
A well-designed oral cosmetics product can use several of these methods simultaneously.
The most important thing is to maintain the correct meaning of each result instead of choosing a term that sounds most effective.
What do the studies on ready-made formulations show?
Previous studies of multi-ingredient products provide evidence regarding the entire formulation
In an earlier four-week study of two-step care, 32 participants completed the entire observation period. Improvements in oral health, hydration, and the measured dimension of the lower lip were noted.[1]
These observations apply to the entire examined scheme.
However, the study did not include a blinded comparison with a suitably matched control, which would have allowed the independent contribution of the tripeptide to be determined.
At the same time, several potentially important ingredients were used.
Therefore, it cannot be concluded that the improvement was solely due to the peptide.
This is a common problem in cosmetic research.
A ready-made formulation can provide real benefits, but at the same time it does not answer the question of whether the ingredient featured on the packaging was necessary to achieve this effect.
The product can, for example, effectively moisturize the lips without showing that the peptide is responsible for the hydration.
A similar problem with the attribution of the effect occurs in a separate two-step study of a product focused on hyaluronic acid.[3]
The study included useful measurements specific to the mouth, but did not directly compare the peptides with the peptide-free formulation.
A more recent study of peptides and hyaluronic acid requires careful interpretation
A 2025 publication described two small studies of a topical formulation containing peptides and hyaluronic acid.[8]
In one, 18 people participated who had not recently undergone filler treatments, while in the other 11 people had previously had their lips enlarged using hyaluronic acid.
Importantly, only two people were included in the placebo group, which made it impossible to conduct a statistically significant comparison between the groups.
The reported clinical results concerned primarily such characteristics as gloss, texture, contour clarity and aesthetic evaluation.
These are legitimate cosmetic effects, but they should not be automatically presented as evidence of significant anatomical enlargement of the lips.
The publication also describes separate, illustrative three-dimensional observations involving six patients from daily practice.[8]
These observations should not be presented as if they were the main endpoint regarding volume in the randomized part of the study.
The distinction between formal research groups and separate illustrative observations should remain clear.
The period after discontinuation of use of the product was particularly interesting.
After about two weeks without the use of the preparation, the previously observed changes returned or almost returned to the initial values.[8]
This is important in the context of durability, because it refutes the automatic interpretation of observed cosmetic effects as permanent structural enlargement.
The study was also funded by the manufacturer, and the authors revealed commercial connections.[8]
Funding does not automatically invalidate the results, but it is an important piece of information when assessing the independence and strength of the evidence.
Overall, the publication provides cautious evidence regarding a specific product.
It does not demonstrate equivalence with injectable fillers, does not confirm that the peptide itself was responsible for the effect, nor does it demonstrate a sustained increase in tissue volume.
Even the term of the study as a „controlled placebo” is insufficient if the placebo group is too small to conduct the planned statistical comparison.
What matters is the actual implementation of the research project, not just its labeling.
Previous use of fillers changes the context of the evidence
People who have previously undergone injectable lip augmentation may be different from people who have never had this procedure.
Initial anatomy, tissue properties, mouth shape, and participants' expectations can influence the interpretation of the effect of the subsequently applied topical product.
Therefore, studies should clearly report the history of previous use of fillers.
Evidence obtained from individuals with previously enlarged mouths may be relevant for this particular population.
However, they should not be generalized automatically to people who have never used fillers.
Similarly, the improvement observed in previously treated patients does not prove that the local peptide preparation prolongs the effect of the injected filler.
Such a claim would require a study designed specifically for this purpose.
Comparing the components would allow a better determination of the peptide's share.
If the goal is to determine whether a specific peptide makes a significant contribution to the product's effect on the mouth, it would be useful to compare two possibly similar formulations in which the main difference is the presence or absence of this peptide.
This would answer a much more precise question than simply observing the improvement after the use of a multi-component mixture.
Claims regarding synergy require even stronger evidence.
To determine whether, for example, a peptide and hyaluronic acid work together better than would be the case if they acted separately, it would be necessary to use appropriate groups with individual components and combinations thereof, and to conduct an analysis that would allow the interaction to be evaluated.
The improvement „before and after” using the mixture does not confirm the synergy.
Similarly, demonstrating the effect of a peptide on cells in laboratory conditions does not mean that the topical product for the mouth delivers the same concentration to the appropriate tissue in humans.
A credible biological mechanism provides a justification for conducting a clinical study.
It does not replace this examination.
The immediate effect, the effect with regular use, and durability are different claims.
The claim that the product „works immediately” differs from the claim that regular use over several weeks results in a certain improvement.
Both are even more different from the statement that the effect remains after discontinuing the product.
Immediate change can result primarily from superficial hydration, optical effects, sensory components, or transient local processes.
The effects that occur during repeated use may have different mechanisms, but if the claim concerns their durability, observation after discontinuation of the product is still necessary.
A study that concludes measurements on the last day of using the cosmetic product cannot confirm a lasting result.
Even if the benefit persists for a limited period of observation after discontinuation, the term „lasting” would require significantly stronger evidence.
The time stated in the cosmetic declaration should therefore correspond to the period actually confirmed in the study.
Irritation and exaggerated claims regarding the augmentation of the lips
Baking is not a specific symptom of the peptide's action
The sensation of warmth, coldness, or tingling may be due to components that are completely unrelated to peptides.
This study clearly shows pro