Peptides in the eye area: creams, serums, eyelash products and a review of the evidence

Peptide products designed for the eye area include eye creams, serums, eyelash and eyebrow preparations, and other cosmetics used in the periorbital region. Although all these products are used on a similar part of the face, they may be intended for completely different tissues and evaluated for different results.

An eye cream can be tested for skin hydration, firmness, elasticity, transepidermal water loss, the appearance of crow's feet, dark circles under the eyes, or other skin characteristics. An eyelash serum, on the other hand, can be evaluated for visible length, thickness, number, alignment, or overall visibility of the lashes. Eyebrow products concern yet another area of hair-bearing skin.

These results should not be equated with each other.

Improving the appearance of the skin under the eyes is not proof of eyelash growth.

An increase in the measured length of the eyelashes does not mean an improvement in the appearance of dark circles under the eyes.

Testing an eyebrow product does not automatically confirm its suitability for use near the eyelid margin.

Similarly, good skin tolerance of a cosmetic product around the eyes does not mean that it has been tested for direct contact with the surface of the eye.

The scientific evidence regarding such products is also very mixed. Some peptide-containing preparations have been evaluated in randomised or controlled trials. In other cases, only small pilot studies, open-label studies or comparisons of results before and after using the product are available.

Therefore, when interpreting research concerning peptide products used around the eyes, it is always worth establishing five basic elements:

1. what exact preparation was studied;
2. where was it used;
3. what were the results compared with;
4. what parameter was actually measured;
5. How long did the examination take?.

This approach limits the risk of transferring results concerning a single product, one part of the face, or one type of measurement to a completely different application.

Why does the eye area require separate assessment?

Several different tissues are located within a small area

The term „eye area” can refer to:

• under-eye skin;
• outer corners of the eyes, where crow's feet appear;
• of the upper and lower eyelids;
• eyelid margin, from which the eyelashes grow;
• Eyebrows;
• conjunctivae;
• tear-jerker;
• ocular surface.

These areas are located very close to each other, but from a biological point of view they are not a single site of exposure.

A product tested on the skin around the eyes has not automatically been evaluated for direct contact with the eye. Similarly, a product tested on the eyebrows does not necessarily have to be suitable for use along the lash line.

Therefore, the full composition of the preparation and its exact intended use are more important than the mere label „peptide”.

In its information regarding cosmetics used around the eyes, the US Food and Drug Administration (FDA) draws attention, among other things, to the intended use of the product, the possibility of contamination, injuries associated with applicators, and irritation. [1]

These are general issues related to cosmetics used near the eyes. They do not constitute proof that the peptides themselves pose a particular hazard to the eye.

Testing of a product intended for this area should therefore specify as precisely as possible:

• place of application;
• frequency of application as part of the study;
• was the product applied along the lash line;
• what local symptoms and signs were observed;
• Was an ophthalmic assessment also carried out?.

The skin around the eye and the ocular surface are two different exposure sites

The cosmetic may be intended for the skin around the eyes, but not for putting into the eye.

Terms such as „eye serum” can sometimes blur this obvious distinction.

The periocular skin remains skin. The surface of the eye, however, encompasses other structures, including the conjunctiva and the corneal surface, which is why the nature of exposure is different.

If a peptide-containing cream was well tolerated when used under the eyes, it does not automatically mean that its direct contact with the surface of the eye has been tested.

Simply put:

eye area cosmetic ≠ eye drops.

The presence of the peptide in the composition does not change this difference.

Skin appearance and eyelash characteristics are different outcomes

A cream designed for the crow's feet area can be evaluated primarily in terms of skin surface, mechanical properties, or the appearance of wrinkles.

The eyelash product, on the other hand, relates to the hair and potentially the processes associated with the hair follicles.

Brow products cover yet another area.

Therefore, each of these objectives requires appropriate measurement methods.

Skin hydration can be assessed instrumentally. The appearance of wrinkles can be analysed using:

• clinical assessment;
• standardised photography;
• skin surface replica;
• profilometries;
• three-dimensional imaging.

In eyelash research, on the other hand, one can measure:

• length;
• width;
• the number of visible hairs;
• orientation;
• darkness;
• volume;
• general visibility.

Measurement of one of these parameters does not automatically confirm the others.

A study published in 2024 evaluated an eyelash serum containing peptides and glycosaminoglycans. The researchers analysed several specific parameters regarding the eyelashes. [2]

These are completely different endpoints to those used in eye cream trials.

For this reason, the result for the serum used on the skin around the eyes cannot be automatically used as evidence regarding eyelash growth.

The appearance of the hair and the biology of hair growth are also not the same thing

Even in eyelash and eyebrow research, a distinction must be made between the visible change and the biological mechanism.

Eyelashes can look more defined for a number of reasons, including a change in:

• lengths;
• thicknesses;
• pigmentation;
• arrangements;
• fragilities;
• hair coverings;
• number of hairs visible in the photograph.

The observed improvement in appearance does not therefore automatically identify the process taking place within the hair follicle.

Similarly, a greater number of visible eyelashes does not mean the formation of new hair follicles.

First, one must precisely determine what was measured. Only afterwards can possible biological explanations be considered.

Facial skin peptide research is background, not proof regarding every under-eye product

Research into peptides used on other parts of the face can provide useful information.

They may, for example, show that a specific peptide or formulation has previously been evaluated in humans.

However, they do not automatically answer questions concerning all products used in the eye area.

What matters are:

• composition of the preparation;
• place of application;
• concentration;
• nature of the exhibition;
• survey population;
• actual endpoint.

An example is the study of palmitoyl pentapeptide conducted on 93 women. A randomised, double-blind, split-face design was used and the preparation was compared with a corresponding moisturiser. The study evaluated fine lines and facial wrinkles. [3]

This is a valuable study concerning a specific formulation and specific skin parameters.

However, it does not constitute independent evidence of:

• eyelash growth;
• increase in eyebrow density;
• reduction of dark circles under the eyes;
• safety of direct eye contact;
• the efficacy of any other eye cream containing the same peptide.

Even two products containing an identically named peptide can differ in concentration, base, pH, chemical stability, other ingredients and place of application.

Therefore, the same peptide name does not mean that two finished cosmetic products are equivalent.

Peptide eye creams and serums

The form of the product does not determine its „potency”

Eye creams usually take the form of a semi-solid emulsion. Serums can be more fluid, gel-like or have the form of a light emulsion.

These differences may affect:

• distribution;
• evaporation rate;
• product retention on the surface;
• Occlusivity;
• sensations after application;
• user preferences.

However, they do not form a universal scale of peptide efficacy.

A serum is not automatically „stronger” than a cream.

A cream doesn't become more effective just because it has a thicker consistency.

Both forms can contain moisturisers, emollients, occlusive ingredients, peptides, antioxidants, niacinamide, botanical ingredients and many other substances.

The moisturizing system itself can affect the look and feel of the skin independently of the action attributed to the peptide.

For this reason, the improvement observed during the study of the multi-component product should primarily be regarded as a result concerning the entire test formulation, unless the experimental design allows the effect of the peptide to be isolated.

A similar principle applies to others creams and moisturisers containing peptidesthe presence of the peptide is one of the elements of the entire formulation, rather than standalone proof of its efficacy.

A greater number of peptides does not automatically mean greater efficacy

The number of different peptides listed in the product's ingredients describes its composition.

However, it is not a validated scale of „power”.

A serum containing several peptides does not automatically become more effective just because the list of peptides is longer.

To demonstrate such a relationship, one would need to compare formulations that are as similar as possible, for example:

• just the substrate without the peptide;
• the same substrate with one peptide;
• the same substrate with a precisely defined combination of peptides.

Without such a comparison, it cannot be stated that a larger number of peptides corresponds to a better result.

What was evaluated in the multi-peptide serum study?

A 2023 study evaluated a multi-peptide eye serum in 32 participants with a mean age of 28.5 years. [4]

For 28 days, the following were evaluated, among other things:

• moisture;
• mechanical properties of the skin;
• imaging of the skin surface in the crow's feet area;
• participants' self-assessment.

The authors described an improvement in several evaluated parameters and reported no adverse reactions attributed to the product during the study period. [4]

The results concern the skin around the eyes.

They are not evidence regarding eyelash growth.

It is also not apparent from the available study description that this was a randomised, matched-background comparison without active ingredients.

Therefore, the most precise interpretation is:

A short-term human study showed changes in several parameters during the use of a specific multi-peptide eye formulation.

This does not mean that:

„the superiority of multiple peptides in under-eye products has been proven.

Nor does it mean that all multi-peptide serums yield similar results.

Participant evaluation and instrumental measurements answer different questions

The subjective assessments of participants can be valuable.

They may concern, among other things:

• perceived smoothness;
• comfort;
• cosmetic properties;
• ease of application;
• perceived hydration;
• perceived improvement in appearance.

However, they are not the same as instrumental measurement.

Statement:

„my skin around the eyes appears smoother”

and the result:

„instrumentally measured surface roughness decreased”

describe two different types of data.

Both may have significance, but they should not be combined into a single, stronger conclusion.

Newer formulations also require critical evaluation

Twenty-two subjects participated in a 12-week study of an eye formulation containing OS-01. [5]

The authors described the changes relative to the initial values in the scope of:

• moisturisation;
• transepidermal water loss;
• firmness;
• flexibility;
• photographic evaluation of several appearance traits.

The preparation also contained other active ingredients. [5]

Cellular ageing was discussed in the theoretical part of the publication. This provides a mechanistic rationale for conducting research on such a formulation.

However, it does not mean that every cosmetic change observed in the participants was caused by the modification of cellular ageing processes.

Human results should remain tied to what was actually measured.

It can therefore be said that during the investigation of a specific formulation, changes in several properties of the skin around the eyes were observed.

A much stronger statement that:

„cream reverses cellular ageing”

it would require additional mechanistic evidence.

Hydration and transepidermal water loss are different parameters

Hydration and transepidermal water loss, referred to as TEWL, are often discussed together, but they do not mean the same thing.

Moisture measurement assesses a specific property related to the water content in the skin.

TEWL concerns the flow of water vapour through the skin.

The preparation may affect both parameters to varying degrees.

None of these measurements in themselves prove:

• increase in collagen synthesis;
• peptide penetration;
• reversal of cellular ageing;
• eyelash growth.

In the OS-01 study, the use of several different measurements avoids treating all skin properties as a single result. [5]

A blinded assessment does not automatically mean a full randomised trial

In a small prospective pilot study of an eye cream containing defensins, eight subjects completed the six-week application period. [6]

The study included:

• participants' feedback;
• imaging;
• instrumental measurements;
• blinded assessment.

Blinding the assessor can reduce some of the errors related to the interpretation of results.

However, this does not automatically mean:

• randomisation;
• blinding of participants;
• applications of matched control substrate;
• of adequate statistical power.

These are distinct elements of the study design.

The small number of participants also limits the ability to broadly generalise the results.

The study can therefore be treated as exploratory data concerning a specific cream containing defensins, rather than as definitive proof regarding all defensins or all peptide eye cosmetics.

Pilot studies have a specific role

Small-scale pilot studies can be useful for:

• detecting potential signals;
• testing of measurement methods;
• feasibility assessments for a larger study;
• formulating new hypotheses.

A small number of participants does not render the study worthless.

However, it means that the results usually require confirmation in larger and better-controlled studies.

This is particularly important when analysing many different endpoints in a small number of people.

Controlled studies allow for more precise comparisons

In two randomised, controlled split-face studies involving 42 and 35 women respectively, three-dimensional imaging was used to evaluate several moisturising preparations applied around the eyes. [7]

The formulations contained combinations including, amongst others:

• niacinamide;
• peptides;
• carnosine;
• other ingredients.

They were compared with untreated skin, rather than with an identical control sample devoid of peptide components.

Such a study can show the difference between the finished product and the area without the preparation.

However, it does not allow the peptide fraction to be isolated.

Furthermore, the results varied between products, studies and individual skin roughness measurements. [7]

This is an important observation.

It shows why one cannot assume that all peptide-based eye creams work in exactly the same way.

A control without product and a control with a substrate answer different questions

A comparison with an area where no product has been applied helps to determine whether the skin has changed compared with the area without the product.

A suitable context, on the other hand, allows us to answer a more specific question:

Does adding the ingredient under investigation produce a greater effect than the cosmetic base alone?

This is of particular importance in research into moisturising products.

The substrate itself can affect:

• moisture;
• smoothness;
• properties of the skin barrier;
• surface appearance.

Therefore, the comparison:

active formulation versus no formulation

does not isolate the effect of the peptide as effectively as:

the active formulation versus its corresponding peptide-free control.

Other small-scale studies provide additional data on the skin

Additional tests include, amongst others:

• an eight-week trial of two peptide creams and a placebo involving 21 women in Indonesia [8];
• A 12-week study of a formulation containing tetrapeptide-68 in 25 women. [9]

These studies provide further data on formulations used around the eyes.

When interpreting the results, however, it is important to bear in mind the sample size and the duration of the observation.

None of these studies automatically confirms:

• eyelash growth;
• brow lift;
• actions that act directly on the surface of the eye;
• the universal effectiveness of all peptide-based under-eye cosmetics.

The improvement in appearance does not indicate penetration of the peptide

A smoother appearance of the skin around the eyes does not mean that the intact peptide molecule has reached the specific cells.

The appearance of the surface can be influenced by, among other things:

• moisture;
• occlusion;
• optical properties;
• the other ingredients of the formulation.

Analytical methods can help in studying the delivery of peptides to the skin.

One publication developed LC-MS/MS methods that enable the quantitative determination of hexapeptides in materials used in skin studies, such as samples obtained by tape stripping or separated layers of skin. [10]

The mere existence of such a method does not mean, however, that every peptide present in the serum under the eyes passes through the skin.

Similarly, the detection of a peptide in a finished cosmetic product confirms its presence in the product, but does not automatically answer the questions:

• whether it remains stable during use;
• whether it penetrates the skin;
• what amount reaches a specific layer;
• whether the molecule remains intact;
• whether it produces the declared clinical effect. [11]

The chain of evidence should remain visible

In the case of locally applied peptides, it is worth dividing the stages into separate groups:

The peptide mentioned in the composition → the peptide is confirmed analytically → the peptide is stable in the formulation → the peptide reaches the appropriate site → it affects a specific biological target → the corresponding effect is observed in humans.

Evidence regarding one stage does not automatically confirm all subsequent stages.

This is an important principle not only for eye products, but also for other peptide-based cosmetics such as peptide lip products, where we must also distinguish the composition of the formulation from its actually measured effects.

Peptide products for eyelashes and eyebrows

Conditioning eyelashes, improving appearance and affecting the hair follicle are different claims

An eyelash product can be intended for:

• covering the surface of the hair;
• improving their flexibility;
• reduction of visible fragility;
• conditioning;
• increase in visual darkness;
• improvement of visibility;
• changes in the specific parameters of the hair.

A much stronger claim that the preparation stimulates biological hair growth requires studies regarding the relevant processes and endpoints.

The longer appearance of the eyelashes does not automatically indicate a mechanism.

Depending on the product and the measurement method, the change could potentially result from:

• less fragility;
• different hair styles;
• greater contrast;
• more visible eyelashes;
• the actual increase in the measured length;
• changes in the hair cycle.

These are not equivalent phenomena.

A higher number of visible eyelashes does not mean the formation of new follicles

The measurement of the number of visible eyelashes refers to the hair that can be detected using a specific imaging method.

A higher number of visible hairs does not automatically mean that new hair follicles have formed.

The result may be influenced by:

• the appearance of hair on the surface of the skin;
• its arrangement;
• contrast;
• image quality;
• the detection threshold set by the software.

The claim that new follicles are being formed would require completely different evidence.

What does the study of formulations containing peptides and glycosaminoglycans show?

Thirty women aged 25 to 65 were included in an open-label study of a product for eyelashes. The eyelashes were evaluated before the start of the study, after four weeks, and after 12 weeks. [2]

High-resolution images and specialized software were used.

The authors described an increase in several parameters compared to the initial values. After 12 weeks, the measured eyelash length was 8.3% longer.[2]

This is a direct human study of a specific formulation for eyelashes.

However, the study did not include a randomized group receiving the base substance alone.

Therefore, it does not allow to determine exactly:

• what part of the change resulted from the product’s action;
• which part could be attributed to the peptide itself;
• whether glucosaminoglycans or other ingredients were of importance;
• how the product would perform in direct comparison with another preparation.

The most cautious conclusion is that changes in certain eyelash parameters were observed during the use of the tested formulation.

An open study is not the same as a lack of evidence

The absence of a randomized control group does not mean that the study does not provide any information.

The study provides:

• observations in humans;
• specific duration;
• defined measurements;
• a signal requiring further investigation.

The possibility of attributing causality is weaker, however.

Therefore, two extreme statements:

„The study proves that peptides cause eyelash growth”

and

„The study shows nothing”

they would be too far-reaching.

The short-term lack of reported adverse reactions has its limitations.

The absence of reported adverse reactions in 30 participants provides information about what was observed in this particular group during the study.[2]

However, this does not mean that:

• rare reactions may not occur;
• longer use has an identical tolerance profile;
• all age groups react in the same way;
• all peptide eyelash products are equally well tolerated.

Information about tolerance should always be related to the size of the group being studied and the length of the observation period.

Peptides and analogues of prostaglandins are different groups of substances

Peptides are molecules made up of amino acids.

Prostaglandin analogues, such as bimatoprost, belong to another chemical and pharmacological group.

Their mechanisms and evidence base should not be combined.

A product labeled as „peptide eyelash serum” should not be automatically considered to work through a prostaglandin-related mechanism.

At the same time, the product's marketing name does not describe its entire composition.

The preparation may contain many different classes of ingredients.

The mere labeling of peptides on the label does not, therefore, prove the absence of other substances.

Marketing labeling is not a complete classification of ingredients

The product can be advertised as:

„peptide serum for eyelashes”

and at the same time contains many other ingredients.

Similarly, the term:

„without prostaglandins”

it answers only one question regarding the composition.

It does not automatically confirm the safety, tolerance or effectiveness of the other ingredients.

In a publication analyzing 79 cosmetic products intended to improve the appearance of eyelashes, analogues of prostaglandins were identified in some of the preparations.[12]

This shows why all eyelash products should not be treated as a single, chemically uniform category.

At the same time, this study did not cover every product available in all markets.

The evidence regarding bimatoprost is not evidence regarding peptide serum.

In a multicenter, randomized, and double-blind study, bimatoprost was compared with a placebo in 278 participants.[13]

After 16 weeks, a majority of the participants receiving bimatoprost met the study-defined improvement criterion, and the imaging results of the eyelashes also indicated a benefit of the active intervention.

Glaucoma occurred statistically more frequently in the active group [13].

These are the results regarding bimatoprost.

They are not evidence regarding peptide eyelash products.

The study shows, however, that different classes of ingredients can have different properties:

• mechanisms;
• clinical research projects;
• data on effectiveness;
• security-related data.

These results should not be transferred between different substances.

Percentages from various studies should not be used as a direct ranking.

If one study of a peptide preparation reports a specific percentage change in eyelash length, and another study of bimatoprost reports a different percentage or proportion of people responding to the intervention, the values from these cannot simply be compared and used to select the „better” product.

The studies may differ:

• population;
• the initial appearance of the eyelashes;
• by imaging method;
• definition of the end point;
• the length of the observation;
• the control group;
• by statistical methods;
• conditions of use.

A reliable comparison requires a study designed specifically to directly compare the interventions.

Eyebrows require separate examinations

Eyebrows and eyelashes are hair-covered structures, but they are located in different places and vary in appearance.

The result regarding the length of the eyelashes does not confirm an increase in brow density.

Similarly, the product tested on the eyebrows was not automatically evaluated for use on the edge of the eyelid.

In a small randomized controlled trial with a placebo control, bimatoprost was evaluated in 20 people with blepharitis [14].

This study concerned bimatoprost, not a peptide cosmetic, but it does well to illustrate the principle of conducting research specific to a particular location.

The available data regarding peptides do not automatically confirm the effectiveness of all products labeled as peptide brow serum.

Conditioning is not a hidden synonym for hair growth

Study showing:

• easier installation;
• smoother surface of the hair;
• less brittleness;
• greater luster;
• user satisfaction

it can support claims regarding conditioning.

It does not automatically confirm the biological changes in the hair follicle.

On the other hand, the actual measurement of a larger hair length remains an important result, even if the mechanism of this change has not been established.

The results of the study of the peptide-glycosaminoglycan formulation constitute a signal requiring further controlled studies, but do not show all the biological steps leading from the application of the product to the observed change. [2]

How to compare the results of different products used around the eyes?

First, the location and actual measurement must be determined.

Products used just a few centimeters apart can use similar marketing terms, even though completely different parameters are evaluated in the studies.

Particular caution is required when determining such things as:

• more complete;
• sturdier;
• smoother;
• upset;
• clearer;
• thicker;
• look younger.

Without a definition of the endpoint, their meaning can be unclear.

The measurement should correspond to the declared effect.

The result from one area should not be used to confirm an entirely different claim.

Dark circles under the eyes are a description of appearance, not a single biological mechanism.

„Dark circles under the eyes” describe the appearance.

They do not indicate a single, uniform biological cause.

If the standardized assessment of the appearance of the under-eye shadows improves in the study, this result refers to the evaluated appearance itself.

It does not automatically rule out the possibility that all the factors responsible for this image are present.

For this reason, the result for hydration and the result for under-eye shadows should be reported separately.

The abscess also requires its own endpoint.

The appearance of puffiness under the eyes can be evaluated using scales, imaging, or other methods.

A change in its appearance does not automatically indicate a cause.

Similarly, a moisturizing preparation cannot be described as reducing edema if this parameter is not measured at all.

Moisture, elasticity and firmness are not the same thing

Humidification assessment devices measure the water-related properties in the skin.

TEWL measures the flow of water through the skin.

Mechanical devices, on the other hand, assess the skin's reaction to a specific deformation and its return to its initial state.

These are different pieces of information.

The mechanical measurement result is not a direct measure of collagen synthesis.

Moisture is not evidence of hair follicle activity.

In study OS-01 these parameters were evaluated separately. [5]

At the same time, comparison with the initial value did not allow the mechanism or the contribution of the specific peptide itself to be fully isolated.

Therefore, the statement about „improvement of firmness” should, if possible, indicate whether it comes from:

• instrumental measurement;
• expert assessments;
• standardized imaging;
• the participant's self-assessment.

Imaging wrinkles and eyelashes has different sources of error

In skin surface studies, it is necessary to monitor, among other things:

• position;
• lighting;
• mimicry;
• time of measurement execution.

Smiling or squinting the eyes can clearly change the appearance of the sheep's lips.

Cosmetic residue and the level of hydration can also affect the measurement.

With eyelashes, the problems are different.

The following may be important:

• correct identification of individual hairs;
• identical area of analysis;
• position of the eyelid;
• contrast;
• control of the use of ink;
• identical rules for detecting hair by the software.

These elements remain important even when the final result is a very precise percentage value.

Precise measurement does not mean certainty about the cause

The device can generate a very accurate numerical value.

This precision applies to measurement.

It does not automatically confirm causality.

The study may accurately show a change, but it still does not have an appropriate control group to determine why the change occurred.

Therefore, the controlled study of the peripheral skin imaging and the open study of the eyelash product represent different levels of evidence regarding causality, even though in both cases advanced measurement technologies were used.[7][2]

The improvement compared to the beginning of the study does not mean an advantage over the background

Comparing with the initial value answers the question:

has the parameter changed during product use?

A comparison with the substrate, however, answers the question:

did the active formulation cause a change other than the product base itself?

These are not the same questions.

Both the active product and its base can, for example, improve hydration, because both contain moisturizing ingredients.

If the active formulation produces a result that is higher than the baseline, comparison between the groups can provide more detailed information.

„Clinically tested” does not say what the research project was.

The product can be described as „clinically tested” after very different types of evaluation.

The term alone does not inform:

• how many participants there were;
• whether a control group was used;
• whether the allocation was randomized;
• whether the participants or the evaluators were blinded;
• how long the examination took;
• what parameters were measured.

The strength of the evidence is determined by the methodology, not by the marketing term alone.

Short-term tolerance and long-term security are different questions

A four- or twelve-week study can describe the events that occur during that period.

He cannot prove that rarer reactions never occur.

Small trials are particularly limited in terms of detecting rare events.

The study of a cosmetic product for the skin around the eyes may also not include a detailed ophthalmological evaluation, like the pharmacological study of a product affecting the eyelashes.

An ocular evaluation was performed in the bimatoprost study. [13]

In cosmetic research, the scope of monitoring may be different.

This does not automatically mean that one product is safer than the other.

It simply means that the scope of the safety assessment was different.

Limits of generalization of research results

Results should not be transferred between different anatomical areas.

The skin test does not confirm eyelash growth just because the product is called an eye serum.

The eyelash examination does not confirm a reduction in dark circles under the eyes.

The brow test does not confirm product tolerance on the surface of the eye.

The multi-peptide serum study evaluated, among other things, hydration, mechanical skin properties, and characteristics of sheep’s lips. [4]

The study evaluated the properties of the eyelashes while evaluating the properties of the hair.[2]

These are two different research questions.

Results should not be transferred between formulations without proper justification

Testing a single peptide or product does not automatically confirm the effectiveness of any product that contains a similar ingredient.

What matters are:

• concentration;
• the substrate;
• pH;
• stability;
• other ingredients;
• packaging;
• nature of the exhibition;
• place of use.

A multipeptide mixture also does not automatically yield all the beneficial results obtained for each of its components under completely different conditions.

Analytical studies of the content of peptides show why the actual formulation of a cosmetic product is important. [11]

The proposed models for assessing the safety of cosmetic peptides, however, can help organize questions about safety, but do not confirm the tolerance or effectiveness of any ready-made eye cream product.[15]

The proposed mechanism is not the same as the mechanism demonstrated in humans

The peptide can be described in the literature as:

• signalling;
• senomorphic;
• supporting extracellular matrix;
• related to growth processes;
• biologically active.

Such terms can justify a research hypothesis.

However, they do not prove that the change in appearance observed in humans occurred through this mechanism.

Study OS-01 provides results regarding skin properties and appearance. [5]

The eyelash serum test provides results regarding hair parameters.[2]

They should not be presented as direct evidence of all the mechanisms discussed in their theoretical part.

Evidence regarding the ingredient and the finished product is at different levels of information.

For a single component, there may be:

• laboratory data;
• analytical characteristics;
• mechanical studies;
• data from other formulations.

The finished cosmetic product can undergo its own clinical study.

These levels should not be combined into one.

For example:

cellular study of peptide X ≠ clinical study of serum under the eyes containing peptide X.

Similarly:

clinical study of one serum with peptide X ≠ evidence regarding all products containing peptide X.

The dosing scheme from the study is not a universal protocol for all peptides.

The method of application used in the study determines the conditions of a specific experiment.

It does not automatically constitute a universal scheme for all peptide cosmetics.

Testing a product under the eyes does not mean that the same preparation has been evaluated for use:

• on the edge of the eyelashes;
• on the eyebrows;
• directly in the eye;
• in another place.

The FDA recommends using eye cosmetics according to their intended purpose and discontinuing use in the event of irritation, and in the case of persistent problems, undergoing an appropriate medical evaluation.[1]

This is general information about eye care cosmetics, and not a specific protocol for the use of peptides.

How to evaluate the evidence regarding peptide products under the eyes?

When analyzing studies or statements regarding such products, it is worth checking the following:

1st Destination

Does the product target the skin under the eyes, the cheeks, the eyelids, the eyelashes or the eyebrows?

2. Precise wording

Was the entire finished product tested, or only a single component?

3. The identity of the peptide

Was a specific peptide defined, or was only the general term „peptidic complex” used?

4. Final point

Was there any testing of moisture, wrinkle depth, firmness, the appearance of the shadows, the length of the eyelashes, the number of visible eyelashes, or any other parameter?

5. Type of comparison

Was the result compared to the initial value, untreated skin, placebo, matched substrate, or another active product?

6. Research project

Was it an open-label, split-face, randomized, blinded, controlled trial or a pilot study?

7. Duration

The four-week and twelve-month studies address different questions.

8. Scope of the safety assessment

Was skin irritation, ocular symptoms, ophthalmological parameters, or only general adverse events observed?

9. Separating the mechanism from the result

Has the proposed biological mechanism actually been measured?

10. No automatic transfer of results

The positive result of one formulation should not be automatically attributed to other products.

Frequently asked questions

1. Are peptide eyelash serums the same as products containing prostaglandin analogues?

No. Peptides and prostaglandin analogues belong to different chemical classes and have different pharmacological and research bases. However, the product may contain many types of ingredients, so the term „peptide serum” on the packaging front does not in itself prove that the composition does not contain substances belonging to other groups. In the analysis of 79 eyelash cosmetics, analogues of prostaglandins were identified in some products. [12] However, this study does not cover all products or all markets. The full composition and data regarding specific substances are more informative than the category name itself.

2. Can an eye serum test confirm eyelash growth?

Only when the eyelashes were actually evaluated using the appropriate parameters in the study. The study of the skin around the eyes itself does not confirm eyelash growth. In the multipeptide serum for the under-eye area, the study evaluated, among other things, hydration, the mechanical properties of the skin, and characteristics of sheep’s wool pads, not eyelash growth. [4] These results should therefore be considered data regarding the skin being studied. The claim regarding the effect on the eyelashes requires studies regarding the eyelashes.

3. What can a multi-peptide serum for the under-eye area actually show?

It can show the changes in these parameters that were actually measured for a specific formulation, population, and period. In the 28-day study, hydration, skin mechanical properties, goat paw characteristics, and participant opinions were evaluated. [4] The available description does not indicate a randomized comparison with a matched control. Therefore, it cannot be determined from it which portion of the change was specifically caused by the peptides or whether a larger number of peptides was better than a smaller one.

4. Is the eye cream stronger than the eye serum?

This cannot be determined based on the product form alone. „Cream” and „serum” primarily describe the characteristics of the formulation, not the standard biological potency. Serum may contain more or less peptide than cream, and both products can vary significantly in their base and other ingredients. Controlled studies of various eye-drop formulations do not establish a universal hierarchy of creams and serums. [7] To determine which product provides a greater effect, a specific parameter and appropriate direct comparison would be needed.

5. Does the improvement in the appearance of the chicken legs prove that the peptide has reached the underlying skin?

No. The reduction in the visibility of wrinkles does not in itself indicate whether the peptide has penetrated the epidermis or at what depth it was acting. Hydration, occlusion, optical properties, and other components can affect the appearance of the skin. Analytical methods that allow the determination of hexapeptides in various materials derived from the skin show that the distribution of the peptide must be examined separately. [10] Even the detection of the peptide in a specific layer does not automatically confirm the biological mechanism.

6. Does improving hydration mean reducing dark circles under the eyes?

No. Hydration and the appearance of eyeshadows are separate endpoints. In the OS-01 formulation study, hydration was evaluated separately from the photographic assessment of the eyeshadows and other appearance characteristics. [5] Improvement in one parameter does not necessarily mean improvement in the other. Additionally, changing the appearance of eyeshadows does not automatically eliminate all the possible factors responsible for their formation.

7. Are there any studies in humans on peptide eyelash products?

Yes. In an open-label study of 30 women over 12 weeks, they used a formulation containing peptides and glucosaminoglycans, and the authors described changes in several eyelash parameters. [2] This is direct evidence for this specific formulation. However, the lack of a randomized group receiving the sole base limits the ability to attribute the results to the peptides. The data should therefore be considered preliminary and specific to the product under study, rather than evidence for all peptide eyelash serums.

8. Does a higher number of visible eyelashes mean the formation of new hair follicles?

No. The number of visible hairs determines the hair detected under specific imaging conditions. A peptide-based study of eyelashes included such a parameter, but did not show the formation of new follicles. [2] The number of visible hairs can be influenced by factors such as their appearance above the skin surface, their arrangement, contrast, and the way the image is analyzed. The formation of new follicles would require completely different evidence.

9. Can self-conditioning alone improve the appearance of eyelashes without stimulating the hair follicles?

Yes. The formulation can affect the hair surface, elasticity, brittleness, texture, or visibility without proven effects on the biological activity of the hair follicle. A study of a product containing peptides and glucosaminoglycans showed changes in several eyelash characteristics, but its open design did not determine all the mechanisms responsible for these observations.[2] Conditioning, reduced brittleness, increased visibility, and changes in the biological growth of the hair remain separate issues.

10. Can the results of the bimatoprost study be used as evidence for peptide serum for eyelashes?

No. Bimatoprost is a different substance and has a separate pharmacological and clinical database. In a large randomized study, it was compared with a placebo and evaluated both eyelash parameters and ocular safety. [13] The results of this study do not show that the peptides act through the same mechanism or produce similar effects. Furthermore, individual percentages derived from different studies should not be compared as if they were a direct test of two products.

11. Does the term „without prostaglandins” mean that the eyelash serum is completely risk-free?

No. This term only indicates the absence of a specific group of ingredients. It does not confirm the safety or tolerance of all other substances present in the finished product. The proposed models for the safety assessment of cosmetic peptides emphasize the need for systematic analysis rather than relying solely on the names of the ingredient categories.[15] The full formulation, the application site, the population studied, the duration of use, and actual data on tolerance are important.

12. Does a study of the product on eyelashes confirm that the same preparation will increase the density of the eyebrows?

Not directly. The eyebrows are a different anatomical area and may require different assessment methods. A small bimatoprost study of the eyebrows illustrates well the need to conduct site-specific studies, although it concerns a different class of substance than peptides.[14] A positive result regarding eyelashes should therefore not be automatically translated into an increase in eyebrow growth.

13. Does the biased evaluation of the photographs mean that a randomized controlled study was conducted?

No. The blinding of the evaluators is only one element of the methodology. Randomization, the type of control group, blinding of the participants, and blinding of the evaluators are separate features of the study. In a small study involving a cream containing defensins, blinded evaluators were used, but the study was still exploratory and only eight people completed it.[6] Blinding can improve the quality of the evaluation, but it does not replace the other elements of a well-controlled experiment.

14. Does the absence of adverse reactions mean long-term safety for the eye area?

No. Such a result describes only what was observed in a specific group and at a specific time. Small cosmetic studies may not detect rare events, and the scope of monitoring may be smaller than in pharmacological studies involving detailed ophthalmological evaluation. The study of a multi-peptide serum for the eyes lasted 28 days. [4] This provides short-term information regarding tolerability, but does not constitute evidence of universal long-term safety.

15. Can the eye cream be used as an eye drop?

No. A product intended for the skin surrounding the eye is not automatically suitable for direct application to the surface of the eye. The FDA emphasizes the importance of using cosmetics according to their intended purpose. [1] The presence of a peptide does not change this principle. Data regarding the skin under the eyes or the eyelids should remain data regarding these areas, and not evidence of tolerance to direct contact with the eye.

16. Does a higher number of peptides in serum predict better results?

No. Available studies do not show a general relationship whereby a higher number of different peptides means greater effectiveness of the product for under-eye use. A study involving 32 participants did not compare identical formulations differing only in the number of peptides. [4] The identity of the peptide, its quantity, stability, vehicle, other ingredients, and the quality of the study are much more important.

17. How best to evaluate claims regarding peptide eye products?

First, the exact composition of the product, the site of use, the parameter being studied, the type of comparison, the design of the study, and the duration of the observation must be determined. Then it is necessary to verify whether the stated claim fits within these data limits. The difference between the study of serum on the skin around the eyes and the open study of the eyelash product shows how important the site and endpoint are. [4] [2] The proposed biological mechanism should also be separated from the actually observed effect in humans.

18. Does „clinically tested” mean that the product has been confirmed in a randomized study?

No. The term „clinically tested” by itself does not define the experimental design. It may refer to an open-label study, a comparison with baseline values, a small pilot study, a split-face design, a controlled trial, or another method. To understand the strength of the evidence, one should check the number of participants, the type of control, randomization, blinding, length of the study, endpoints, and statistical analysis.

19. Can better hydration make fine lines around the eyes less noticeable?

It can affect their appearance because the water content and surface properties of the skin can change its texture. However, this does not automatically result in new collagen formation or deeper tissue remodeling. That is why in studies, hydration and the appearance of wrinkles are often evaluated separately. The claim of a peptide-dependent structural change requires additional evidence beyond observation that the skin is better hydrated or looks smoother.

20. Does instrumental measurement of greater firmness prove an increase in the amount of collagen?

No. The instruments assess the mechanical behavior of the skin under specific measurement conditions. They do not directly measure the amount of newly synthesized collagen. In the OS-01 formulation study, firmness and elasticity were one of several separate endpoints. [5] These results should therefore remain a description of the mechanical properties of the skin, unless separate studies directly confirm the collagen-related mechanism.

21. Are dark circles a problem that a peptide can simply „treat”?

This should not be interpreted in this way. The shadows under the eyes describe the appearance, not a single unified biological mechanism. Cosmetic testing can assess whether their visibility has changed under certain conditions. However, this does not mean that the product has eliminated all possible factors responsible for such appearance. If the photographic assessment of the shadows improved in the test, the most precise conclusion remains the improvement of that specific appearance parameter.

22. Can a product that is well tolerated under the eyes be unsuitable for the eyelash line?

Yes. These are different exposure sites. The product can be intended and tested on the eye-surrounding skin, but not on the eyelid edge. When applied closer to the eye, the migration of the product, the nature of the ingredients, and the possibility of contact with the eye surface can all play a role. Therefore, data on skin tolerance under the eyes should not be automatically extended to use along the lash line.

23. Does the detection of the peptide in the skin mean that it is working?

No. Detecting a peptide in a specific layer of skin would be important evidence regarding the delivery of the molecule, but it does not in itself confirm a biological or cosmetic effect. It would still have to be determined whether the peptide remained in the appropriate form, whether it interacted with the intended target, and whether it led to a measurable result. Data on penetration and data on the clinical effect complement each other, but are not the same.

24. Can the results of a multi-ingredient eye cream be attributed to the designated peptide?

Not automatically. If a product contains several functional ingredients, a clinical study primarily assesses the entire formulation. Without an appropriately matched control product differing only in the presence of a specific peptide, it is difficult to determine the independent contribution of this component. This problem applies to several of the eye-care products discussed. [5] [7] Therefore, it is more reasonable to report the result for the entire formulation than to attribute each observed change to a single identified component.

Limitations of the available evidence

The literature regarding peptide products used around the eyes has several recurring limitations.

First of all, the term „product under the eyes” covers many different anatomical areas.

The skin under the eyes, the earlobes, the eyelids, the eyelashes, the eyebrows and the surface of the eye should not be treated as a single tissue.

Secondly, many of the tested preparations contain several functional ingredients.

The study of the finished formulation does not therefore automatically isolate the peptide component.

Thirdly, many available studies involve small groups.

The aforementioned publications included studies from:

• eight people who completed the study [6];
• 21 participants [8];
• 22 participants [5];
• 25 participants [9];
• 30 participants [2];
• 32 participants [4].

Such studies can provide useful data in humans, but they limit the ability to generalize the results and detect rare adverse events.

Fourthly, some of the research is based primarily on a comparison with the initial value, rather than with a suitably matched background.

A change from the beginning of the study does not provide the same possibility of attributing causality as a well-designed comparison of the active preparation with an appropriate control product.

Fifthly, the use of advanced instruments does not eliminate the need for an appropriate control group.

A very accurate measurement can show that a change has occurred, but it does not necessarily explain its cause.

Sixthly, the proposed mechanisms often go beyond what was directly evaluated in a clinical study.

The peptide can be discussed in the context of cellular signaling, extracellular matrix, cellular aging, or hair-related processes, whereas the human study only measures appearance or physical properties.

Seventhly, data regarding a component should not be automatically transferred between different finished products.

The concentration, stability, base material and other components are important.

After the eighth, the results obtained in one anatomical location should not be automatically transferred to others.

Studies of facial wrinkles do not confirm the growth of eyelashes on their own.

Studies of eyelashes do not confirm a reduction in dark circles under the eyes.

Brow studies do not confirm tolerance through the eye surface.

Finally, short-term good tolerance is not the same as universal long-term safety.

This is particularly important for products used very close to the eyes.

Summary

Peptide products used around the eyes fall into several fundamentally different categories of cosmetics.

Creams and cheese under the eyes primarily affect the skin surrounding the eye.

Eyelash serums concern the appearance and parameters of the hair.

Brow products cover yet another area.

The fact that all these preparations are used close together does not mean that the evidence regarding them is interchangeable.

Available studies in humans provide some data regarding specific peptide formulations.

In a 28-day multi-peptide serum eye study, changes in hydration, skin mechanical properties, parameters related to crow’s feet, and participant assessments were described [4].

In other studies, formulations for the under-eye area were evaluated for, among other things, hydration, periorbital water loss, firmness, elasticity, wrinkles, and other appearance characteristics.[5–9]

In a 12-week open-label study of a formulation containing peptides and glucosaminoglycans, changes were observed in several eyelash parameters, including measured length.[2]

These studies, however, differ significantly in terms of:

• number of participants;
• comparative groups;
• blindness;
• duration;
• formulation;
• anatomical location;
• the evaluated parameters.

The available evidence therefore does not confirm a single universal „peptides-around-the-eye effect”.

The most important distinctions can be summarized as follows:

the skin around the eye ≠ the surface of the eye

eye cream ≠ mascara serum

evidence regarding eyelashes ≠ evidence regarding eyebrows

moisturizing ≠ improvement of dark circles under the eyes

measurement of firmness ≠ direct evidence of collagen synthesis

more visible lashes ≠ the formation of new follicles

conditioning ≠ proven stimulation of the hair follicle

The peptide present in the cosmetic product ≠ the peptide delivered to the appropriate layer of the skin

Peptide detected in the skin ≠ proven clinical effect

more peptides ≠ automatically greater effectiveness

improvement compared to the initial value ≠ superiority over the substrate

Short-term good tolerance ≠ universal long-term safety

and

Peptide serum for eyelashes ≠ a product based on a prostaglandin analogue.

The most reliable interpretation remains therefore specific:

it is necessary to determine the formulation, the site of application, the actually measured parameter, the type of comparison, the duration of the study and its limitations.

Disclaimer

The article is purely educational and scientifically informative in nature. It discusses cosmetic formulations containing peptides, research on the skin around the eyes, products for eyelashes and eyebrows, the methodology of research, different classes of ingredients, and available scientific publications. It does not constitute medical, ophthalmological, or dermatological advice and is not a recommendation for the use of a specific eye cream, serum, eyelash or eyebrow product, a prostaglandin analogue, or any other cosmetic or pharmaceutical product. The results regarding a single peptide, formulation, concentration, anatomical location, population, or study design should not be automatically extrapolated to other products. Cosmetics intended for the skin around the eyes should not be considered suitable for direct contact with the surface of the eye based solely on the composition. Persistent redness, pain, swelling, visual disturbances, significant irritation, or suspicion of an allergic reaction require appropriate evaluation by a qualified healthcare professional.

References

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