Hydrogel facial mask for sensitive skin: A pilot study of long‐term effects on hydration, barrier function and mechanical properties

Abstract

Hydrogel‐based facial masks are commonly used in skincare, yet their long‐term effects in sensitive skin remain insufficiently characterized. In this study, we investigated the safety, tolerability and functional performance of a hydrogel facial mask based on poly(N‐vinyl pyrrolidone) (PVP), poly(ethylene glycol) (PEG‐400) and agar, incorporating bioactive compounds (hyaluronic acid, ectoine, allantoin and tocopherol). The hydrogel was manufactured using radiation‐induced crosslinking technology originally developed for medical applications and evaluated in individuals with sensitive and allergy‐prone skin, with particular emphasis on hydration, skin barrier function and mechanical properties. The safety of the formulation was initially confirmed in a patch test (n = 30), followed by a 6‐week open‐label, baseline‐controlled study (n = 15). Skin hydration, transepidermal water loss (TEWL), sebum level, mechanical properties, skin colour and pH were assessed using instrumental methods. Short‐term dynamics after a single application were additionally evaluated, and the biological activity of the formulation was assessed in vitro using human dermal fibroblasts to quantify extracellular matrix (ECM) protein synthesis. Repeated application of the hydrogel mask resulted in progressive improvement in skin hydration and firmness, without measurable adverse effects on barrier‐related parameters, sebum production, skin colour or pH. Short‐term responses were transient and consistent with occlusion‐driven modulation of the skin microenvironment, rather than sustained post‐application effects. In vitro exposure to hydrogel‐derived eluates induced a time‐dependent increase in collagen and elastin synthesis, indicating biologically relevant cellular activity. The results indicate that the hydrogel formulation combines high tolerability with measurable functional efficacy through complementary physicochemical (hydration and occlusion) and biological (ECM‐related) mechanisms, supporting its potential suitability for repeated use in the care of sensitive and allergy‐prone skin.

A hydrogel facial mask based on radiation‐crosslinked medical‐grade hydrogel technology improved hydration and skin firmness while maintaining barrier integrity and tolerability in sensitive skin. The simplified formulation demonstrated both physicochemical and biologically relevant cellular effects.

INTRODUCTION

Facial masks are widely used in skincare to modulate skin hydration and improve skin condition [1, 2]. Among the available formulations, hydrogel‐based systems have attracted considerable attention due to their high water content and three‐dimensional polymer structure able to closely conform to the skin surface [2, 3]. This intimate contact with the skin promotes the formation of a transient hydrated and semi‐occlusive microenvironment, which may alter the skin microenvironment and influence water distribution within the stratum corneum [4, 5].

Despite their widespread use, most studies on hydrogel masks focus on short‐term effects observed after a single application, such as temporary increases in skin hydration and smoothness [6]. However, cosmetic products are typically applied repeatedly over extended periods, and data addressing the cumulative and long‐term effects of hydrogel‐based formulations under real‐use conditions remain limited. In particular, the long‐term effects of repeated applications on skin barrier function and mechanical properties have not been sufficiently characterized.

Sensitive and allergy‐prone skin is characterized by increased reactivity and altered barrier function, which may affect both the efficacy and tolerability of topical formulations [7, 8, 9, 10]. In such conditions, maintaining skin hydration while supporting barrier function is particularly important. Therefore, the evaluation of cosmetic formulations intended for sensitive skin requires a balanced assessment of efficacy, tolerability and their impact on skin homeostasis. Sensitive skin affects a substantial proportion of the population, with prevalence estimates ranging from 40 to 60% depending on the population, age and other assessment criteria, highlighting its clinical and cosmetic relevance [11]. At the physiological level, sensitive skin is often associated with impaired barrier function, increased transepidermal water loss, altered lipid organization and heightened neuro‐sensory reactivity, which collectively contribute to increased susceptibility to irritation [12]. Sensitive skin is increasingly recognized as a condition involving both barrier dysfunction and altered neuro‐sensory responses, rather than a purely subjective phenomenon.

Hydrogel‐based formulations may act not only as passive carriers but also as systems capable of modulating the skin microenvironment. Their high water content and close contact with the skin surface can create transient occlusive conditions, which may enhance hydration and facilitate the interaction of incorporated bioactive compounds with the stratum corneum [5, 13]. Under these conditions, hydration‐dependent changes in the stratum corneum may influence barrier‐related parameters, mechanical behaviour and the accessibility of active ingredients to superficial skin layers [14, 15, 16]. These processes may also contribute to transient changes in the elasticity of the stratum corneum, influencing its mechanical properties and permeability. Such hydration‐driven effects may simultaneously modulate both barrier‐related parameters and mechanical properties of the skin, linking physicochemical interactions with functional skin responses.

In addition to their physicochemical properties, hydrogel systems may serve as carriers of biologically active compounds that contribute to skin function through complementary mechanisms. For instance, hyaluronic acid is known for its hygroscopic properties and ability to enhance water retention in the stratum corneum [17]. Ectoine, a compatible solute, has been reported to stabilize cellular structures and reduce stress‐induced inflammation, supporting barrier function and skin tolerance [18]. Allantoin exhibits soothing, anti‐inflammatory and skin‐conditioning properties and is widely used in cosmetic formulations for sensitive and irritated skin [19, 20], whereas tocopherol provides antioxidant protection against oxidative stress [21]. Together, these components may act through complementary mechanisms, supporting hydration, barrier stability and protection against environmental stress [22]. The combination of these components within an aqueous hydrogel matrix may therefore synergistically contribute to both immediate physicochemical effects and longer‐term functional responses of the skin.

Although the penetration of cosmetic ingredients is typically limited to the superficial layer of the skin, their interaction with epidermal structures may influence skin hydration, barrier‐related processes and indirectly affect the condition of deeper skin layers. Therefore, evaluation of hydrogel systems should consider both physicochemical effects and potential biologically relevant responses. Moreover, there is increasing interest in formulations with simplified and well‐defined compositions, particularly for sensitive skin, where minimizing the number of components reduces the risk of irritation, yet maintaining functional effectiveness.

To date, studies integrating long‐term in vivo evaluation with short‐term mechanistic assessment and in vitro analysis of extracellular matrix‐related responses remain scarce, particularly in the context of hydrogel‐based formulations designed for sensitive skin. This multidimensional approach is particularly relevant for understanding both immediate physicochemical effects and longer‐term functional and biological responses of the skin.

The aim of the present study was to evaluate the safety, tolerability and effects of a hydrogel facial mask on skin biophysical parameters in individuals with sensitive and allergy‐prone skin over a 6‐week period. The hydrogel used as a carrier matrix in this work is based on radiation‐induced crosslinking technology originally developed for medical applications and provides a well‐defined and stable polymer network with high water content and reproducible properties. The study combined instrumental in vivo assessment in human volunteers of skin hydration, transepidermal water loss (TEWL), sebum level, mechanical properties, colour and pH with an in vitro evaluation of extracellular matrix protein synthesis. In addition, a short‐term exploratory assessment was performed to characterize immediate skin responses and support interpretation of long‐term observations. This integrative approach provides complementary information on both the functional performance and the biological activity of the hydrogel formulation.

MATERIALS AND METHODS

Materials

Poly (N‐vinyl pyrrolidone) (PVP, K‐90), poly (ethylene glycol) (PEG‐400), sodium salt of hyaluronic acid and agar were purchased from BASF, Sigma‐Aldrich, Contipro a.s., and BD (Becton, Dickinson and Company), respectively. Ectoin (Sigma‐Aldrich), allantoin (Sigma‐Aldrich) and tocopherol (Kerfoot Group Ltd) were used as received.

Hydrogel formulation

The tested material was a facial mask composed of a hydrogel matrix based on crosslinked hydrophilic polymers and selected active compounds. The hydrogel was obtained via radiation‐induced crosslinking using a procedure based on the so‐called Rosiak's method developed for hydrogels for medicine, which employs ionizing radiation to form a three‐dimensional polymer network in aqueous systems [23].

The reaction mixture was prepared by dissolving polymeric components and additives in water at elevated temperature (over 60°C) under continuous mixing to ensure homogeneity. The resulting solution was then cast into moulds corresponding to the shape of a facial mask and allowed to solidify. The samples were subsequently sealed in polymer packaging and irradiated. Crosslinking of the synthetic polymer of PVP was performed using an electron beam generated by a 6 MeV linear accelerator (ELU‐6, Russia). An irradiation dose of approximately 25 kGy, determined by calorimetric dosimetry, was applied to induce covalent network formation, which resulted in a stable hydrogel with high water content and a well‐defined three‐dimensional structure and, moreover, greatly reduced the level of microorganism in the product.

The formulation contained compounds with moisturizing, soothing and protective properties, including hyaluronic acid, ectoine, allantoin and tocopherol.

The hydrogel system was designed to ensure close contact with the skin surface and appropriate mechanical integrity, enabling reproducible application conditions. The formulation was prepared under controlled laboratory conditions to ensure reproducibility of the material properties (Figure 1).

FIGURE 1.

Representative photographs of the hydrogel facial mask used in the study: (a) hydrogel mask immediately after preparation, showing the transparent crosslinked hydrogel structure and facial mask geometry, and (b) application of the hydrogel mask on facial skin during use. [Colour figure can be viewed at wileyonlinelibrary.com]

Preliminary safety assessment — Patch test

The skin tolerability of the hydrogel mask was evaluated using a patch test conducted on human volunteers. The study was performed in accordance with the principles of the Declaration of Helsinki and relevant European regulations, following standard dermatological testing guidelines.

A total of 30 healthy volunteers (aged 18–75 years), including individuals with self‐reported sensitive and allergy‐prone skin, were enrolled in the study. All participants provided informed consent prior to inclusion. During the study period, participants were instructed to avoid medications and topical products that could influence skin responses.

The tested hydrogel formulation and a control hydrogel matrix without bioactive components, both measuring 10 mm × 10 mm, were applied under occlusive conditions using patch chambers fixed to the skin on the upper back (interscapular region). The patches were removed after 48 h and skin reactions were assessed by a dermatologist at defined time points (immediately after patch removal, 24 h and 72 h after application). Skin response was evaluated using a standard dermatological scoring scale for irritation and sensitization.

Study population and experimental design

A long‐term skin response study was conducted on a group of adult volunteers with self‐declared sensitive and allergy‐prone skin. Classification of sensitive skin was based on self‐reported characteristics, reflecting real‐life consumer conditions rather than strictly clinical criteria. The final analysis included 15 participants (12 females and 3 males, aged 33–55 years) with different skin types, with 5 participants presenting reduced baseline hydration (including 2 with very dry skin). All participants self‐reported sensitive and/or allergy‐prone skin. The study was an open‐label, baseline‐controlled investigation and was conducted under controlled laboratory conditions. The study protocol complied with the principles of the Declaration of Helsinki and was approved by the Ethics Committee of Nicolaus Copernicus University in Torun (KB 67/2021). The study was designed to reflect real‐use conditions, focusing on intra‐individual changes over time rather than comparison with a placebo or reference formulation. All participants were informed about the study procedure and provided written informed consent prior to inclusion.

Participants received detailed guidance regarding the application procedure to ensure consistent use of the product, namely they were instructed to apply the hydrogel mask three times per week for a period of 6 weeks. The mask was applied to cleansed facial skin and left in place for 20 min during each application. The hydrogel mask was carefully applied to ensure uniform adhesion to the skin surface, particularly in the under‐eye region. Participants maintained their usual skincare routine throughout the study and did not introduce new cosmetic products in order to minimize the risk of skin irritation and external interference with the results.

Skin hydration, transepidermal water loss (TEWL), mechanical properties and sebum levels were assessed at predefined time points: before the start of product application (baseline, time 0), and after 2, 4 and 6 weeks of regular mask use. Skin colour and pH were evaluated at time 0 and after 6 weeks of application. All measurements were performed on predefined areas of facial skin, primarily on the cheek region, under controlled environmental conditions (temperature 20–22°C, relative humidity 40–60%) following an acclimatization period of at least 20 min. The same predefined anatomical sites, including those used for Visioscope image acquisition, were maintained throughout the study for each participant. Before each measurement session, participants were instructed to avoid application of cosmetic products on the test area for at least 12 h and to refrain from washing the face immediately before the visit.

Instrumental skin measurements

An objective assessment of skin condition was performed using a Multi Probe Adapter System (Courage & Khazaka Electronic GmbH, Cologne, Germany) equipped with dedicated probes for the evaluation of biophysical skin parameters. The following devices were used: Corneometer® CM 825 (skin hydration), Tewameter® TM Hex (transepidermal water loss, TEWL), Sebumeter® SM 815 (sebum level), Cutometer® MPA 580 (skin elasticity), Indentometer® IDM 800 (skin firmness) and Skin‐Colorimeter® CL 400 (skin tone parameters L*, a*, b*, ITA°), and a pH meter (Elmetron, Poland) equipped with a combined EPX‐3 electrode designed for measuring the pH of flat surfaces, including the skin. Additionally, standardized high‐resolution images of the skin surface were obtained using a Visioscope® PC 35 camera.

All measurements were performed according to the manufacturers' guidelines, with probes applied perpendicular to the skin surface and minimal pressure to avoid measurement artefacts. Each parameter was measured in at least three consecutive repetitions, and the mean value was used for further analysis.

Short‐term skin response after a single application

A short‐term exploratory pilot assessment was performed to evaluate the immediate skin response following a single application of the hydrogel mask. The assessment was conducted on two adult volunteers under controlled laboratory conditions. All measurements were performed under controlled environmental conditions (temperature 20–22°C, relative humidity 40–60%) following an acclimatization period of at least 20 min. The product was not reapplied during the observation period, allowing evaluation of post‐occlusion effects and short‐term recovery of the skin barrier.

Skin parameters were measured at baseline (time 0), followed by a single 30‐min application of the hydrogel mask. After mask removal, subsequent measurements were performed at defined time points over a total observation period of up to 3.5 h, in order to capture the dynamics of post‐application skin responses. Selected skin parameters, including skin hydration, transepidermal water loss (TEWL), sebum level and skin colour, were assessed using the same instrumental methods as in the main study.

Due to the limited number of participants, these results should be interpreted with caution and regarded as exploratory and primarily mechanistic in nature.

In vitro assessment of extracellular matrix protein synthesis

The biological activity of the hydrogel formulation was evaluated in vitro using human dermal fibroblasts (ATCC®, PCS‐201‐012), focusing on the effect of hydrogel‐derived eluates on the synthesis of extracellular matrix (ECM) proteins, including collagen and elastin.

Hydrogel‐derived eluates were prepared by incubating samples in cell culture medium (0.2 g/mL) at 37°C for 2 h, in accordance with ISO 10993‐12 guidelines. The eluates were collected and used for further experiments, with the medium volume adjusted to account for hydrogel swelling.

Fibroblasts were cultured in Fibroblast Basal Medium (ATCC®, PCS‐201‐030) supplemented with a Fibroblast Growth Kit Low Serum (ATCC®, PCS‐201‐041) and maintained at 37°C in a humidified atmosphere with 5% CO₂. Cells were seeded in 96‐well plates (6 × 10⁴ cells/mL, 100 μL per well) and, after 24 h, the medium was replaced with eluate‐containing medium. The eluates were tested, with cells cultured in standard medium serving as the control group. All reagents were used according to the manufacturer's instructions.

ECM protein synthesis was assessed after 24, 48 and 72 h using a fluorescent probe (Col‐F, Biorbyt, cat. no. 6346) that binds to collagen and elastin. Cells were washed with phosphate‐buffered saline (PBS), incubated with the probe for 30 min at 37°C, and fluorescence intensity was measured using a microplate reader (excitation: 490 nm, emission: 520 nm). Results were expressed as relative fluorescence intensity normalized to the control group.

Statistical analysis

Data are presented as median and interquartile range (IQR) for in vivo measurements and as mean ± standard deviation (SD) for in vitro experiments. For in vivo measurements, differences between repeated time points were evaluated using the Friedman test for repeated measures. When the overall test was significant, pairwise comparisons were performed using the Wilcoxon signed‐rank test with Bonferroni correction. The effect size was estimated using Kendall's coefficient of concordance (W). To assess the association between baseline skin condition and treatment response, Spearman's rank correlation coefficient was calculated between baseline hydration values and relative hydration change after 6 weeks of hydrogel mask application. For in vitro experiments, statistical differences between groups were evaluated using one‐way analysis of variance (ANOVA) followed by Tukey's post hoc test. All statistical analyses were performed using OriginPro 2023 (OriginLab Corporation, Northampton, MA, USA). A p‐value <0.05 was considered statistically significant.

Subjective evaluation of the hydrogel mask

Subjective evaluation of the hydrogel mask was performed to assess participants' perception of product performance under real‐use conditions. The assessment was conducted using a structured questionnaire completed by participants after the 6‐week study period.

Four parameters were evaluated: comfort during application, ease of application, perceived immediate skin effect and general mask assessment. Each parameter was rated using a 7‐point Likert‐type scale ranging from −3 to +3, where −3 indicated a strongly negative perception (e.g. ‘strongly dislike’), 0 represented a neutral response (‘no opinion’), and + 3 indicated a strongly positive perception (e.g. ‘strongly like’). Participants were instructed to base their responses on their experience during the study period. The questionnaire captured both functional and sensory aspects of hydrogel mask use, including handling characteristics and perceived effects on the skin.

RESULTS AND DISCUSSION

Skin tolerability and safety

As an initial step, the skin tolerability of the hydrogel formulation was assessed using a standardized patch test to verify the absence of potential irritation or sensitization effects. The test was performed on 30 volunteers, including individuals with self‐reported allergy‐prone skin. The application method, application sites and representative results are illustrated in Figure 2.

FIGURE 2.

Representative images of patch test application on the upper back (interscapular region): (a) immediately after application, (b) after 48 h with patches in place and (c) 48 h after patch removal. [Colour figure can be viewed at wileyonlinelibrary.com]

No positive skin reactions indicative of irritation or sensitization were observed in any of the participants at any evaluated time point, including immediately after patch removal, after 48 h of occlusive exposure, and at the 72‐h follow‐up. All test sites were classified as negative according to the applied dermatological scoring scale. This included participants with self‐reported sensitive and allergy‐prone skin, among whom no adverse skin responses were observed. These findings indicate that the tested hydrogel formulation did not exhibit irritating or sensitizing potential under the conditions of the study and was well tolerated by all participants.

The high tolerability demonstrated in the patch test is particularly relevant in the context of sensitive skin, where barrier instability and increased reactivity often limit the use of cosmetic formulations. These results provide a basis for further evaluation of the hydrogel formulation under repeated‐use conditions and support its suitability for use in individuals with sensitive and allergy‐prone skin.

Effects on skin hydration

Skin hydration was assessed on the cheek using corneometric measurements at the initial time point (baseline) and after 2, 4 and 6 weeks of regular hydrogel mask application. The individual responses of participants are presented in Figure 3, while the statistical evaluation of the results is shown in Figure 4.

FIGURE 3.

Individual changes in skin hydration measured by corneometry at week 0 and after 2, 4 and 6 weeks of hydrogel mask application. Data are presented for each participant to illustrate inter‐individual variability in response to the treatment. To further assess the influence of baseline skin condition on treatment response, correlation analysis between baseline hydration and relative hydration improvement after 6 weeks was subsequently performed. [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 4.

Statistical evaluation of skin hydration during hydrogel mask application: (a) Skin hydration measured at baseline and after 2, 4 and 6 weeks of treatment. Boxplots represent the median, interquartile range (IQR) and range, with individual data points overlaid. A significant increase in hydration was observed after 6 weeks (**p < 0.01). (b) Correlation between baseline skin hydration and relative change in skin hydration after 6 weeks of hydrogel mask application. Each point represents an individual participant. A significant negative correlation was observed (Spearman ρ = −0.71, p = 0.003), indicating greater hydration improvement in participants with lower baseline hydration levels.

The individual data presented in Figure 3 reveal considerable inter‐individual variability in hydration changes over time. While a tendency towards increased hydration can be observed in a substantial proportion of participants, the magnitude and direction of changes differ between individuals, particularly at earlier time points. This heterogeneity reflects the biological variability of skin condition and response to topical treatments.

To determine whether these visually observed changes were statistically significant at the group level, a non‐parametric analysis for repeated measures was performed. Differences between time points were assessed using the Friedman test, followed by post hoc pairwise comparisons (Wilcoxon signed‐rank test with Bonferroni correction). To further investigate the relationship between baseline skin condition and treatment response, Spearman's rank correlation analysis was performed between baseline hydration values (week 0) and relative hydration change after 6 weeks of treatment. The results of these analyses are presented in Figure 4.

The statistical analysis confirmed a time‐dependent effect of the hydrogel formulation on skin hydration. Repeated application of the hydrogel mask resulted in a measurable and statistically significant improvement in skin hydration after prolonged use. Median hydration values showed moderate fluctuations over time, changing from 67.8 units at baseline (IQR: 57.8–81.6) to 65.4 units after 2 weeks (IQR: 60.5–69.1), followed by an increase to 68.3 units after 4 weeks (IQR: 58.3–77.6) and reaching the highest median value of 72.2 units after 6 weeks (IQR: 62.0–92.3). Despite a transient decrease after 2 weeks, the overall trend indicated progressive improvement in skin hydration with continued hydrogel mask application. The observed inter‐individual variability is consistent with differences in baseline skin condition, barrier function and individual responsiveness commonly reported in in vivo cosmetic studies [24].

Importantly, the magnitude of hydration improvement appeared to be associated with the initial skin condition. Correlation analysis revealed a significant negative relationship between baseline hydration and relative hydration improvement after 6 weeks of hydrogel mask application (Spearman ρ = −0.71, p = 0.003). Participants with lower initial hydration levels generally exhibited greater relative increases in skin hydration following treatment, whereas individuals with higher baseline hydration showed smaller relative changes. In individual cases, relative hydration improvement exceeded 100%, particularly among participants with initially dehydrated skin, as a consequence of their low baseline hydration values. These findings suggest that the hydrogel formulation may be particularly beneficial for skin with lower initial hydration levels. The observed variability in treatment response is consistent with the heterogeneous nature of skin physiology and is commonly reported in in vivo cosmetic studies.

The observed effects can be attributed to the physicochemical properties of the hydrogel system. During application, the hydrogel provides a high‐water‐content environment and maintains close contact with the skin surface, creating a hydrated and mildly occlusive microenvironment that may support gradual enhancement of water content in the stratum corneum rather than being limited to an immediate effect. With repeated use, this may lead to progressive improvement in water retention and stabilization of hydration‐related processes over time. In addition, the presence of hygroscopic and protective compounds such as hyaluronic acid and ectoine may further contribute to water retention within the stratum corneum and support hydration‐related processes [25, 26].

Effects on skin barrier function (TEWL)

To complement hydration measurements, transepidermal water loss (TEWL) was assessed as an indicator of skin barrier function during the 6‐week study period. The individual responses of participants are presented in Figure 5, while the statistical evaluation of the results is shown in Figure 6.

FIGURE 5.

Individual transepidermal water loss (TEWL) values for each participant at initial time and after 2, 4 and 6 weeks of hydrogel mask application, illustrating inter‐individual variability over time. [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 6.

Time‐dependent changes in transepidermal water loss (TEWL) during the 6‐week hydrogel mask application period. Data are presented as boxplots showing the median, interquartile range (IQR), and range, with individual data points overlaid. No statistically significant changes in TEWL were observed over time, indicating preservation of skin barrier function during repeated application of the hydrogel mask.

Initial TEWL values were within the physiological range reported for healthy facial skin (approximately 5–25 g/m²/h) in nearly all participants, with only one individual exhibiting elevated baseline TEWL values (Figure 5) [27]. This indicates that the study population predominantly consisted of individuals with an intact skin barrier at baseline. The individual data demonstrate noticeable inter‐individual variability over the experimental period, with TEWL values fluctuating in both directions. However, these changes did not follow a consistent temporal pattern and are therefore considered to reflect physiological variability rather than a treatment‐related effect. A single participant exhibited consistently elevated TEWL values throughout the study period (approximately 27–34 g/m²/h). Importantly, no progressive increase was observed in this case, suggesting that repeated application of the hydrogel mask did not worsen pre‐existing barrier impairment.

In general, no sustained change in TEWL was detected following prolonged application of the formulation. The statistical analysis did not reveal significant time‐dependent variation in TEWL over the course of the study (Friedman test, p > 0.05). Median TEWL values remained within a comparable range across all time points, showing only minor fluctuations without a consistent increasing or decreasing trend (Figure 6). This finding indicates that the hydrogel mask did not induce measurable disruption of skin barrier function under the study conditions. The preservation of barrier function may also be supported by the presence of ectoine and allantoin, which are known to stabilize cellular structures, improve water retention and support skin barrier integrity under environmental or hydration‐related stress [18, 28, 29]. The observed stability of TEWL is particularly relevant for hydrogel‐based systems, which transiently the skin microenvironment through hydration‐related effects. In the context of the increase in skin hydration (Section 3.2), these findings suggest that the hydrogel formulation supports skin homeostasis while enhancing hydration without compromising barrier integrity.

Effects on skin mechanical properties

To further characterize the effects of the hydrogel formulation, skin mechanical properties were evaluated using Indentometer and Cutometer measurements. The results are presented as individual responses (Figure 7a, Indentometer) and as statistical distributions (Figures 7b and 8).

FIGURE 7.

Changes in skin firmness assessed by Indentometer: (a) individual responses of participants and (b) distribution of values (median and interquartile range) during the 6‐week study period (n = 15). Asterisks indicate statistically significant differences compared to time 0 (**p < 0.01). [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 8.

Changes in skin mechanical parameters assessed by Cutometer during the 6‐week study period (median and interquartile range, n = 15): (a) R0 (skin deformation), (b) R2 (overall elasticity), (c) R5 (net elasticity) and (d) R7 (elastic recovery). Asterisks indicate statistically significant differences compared to baseline (*p < 0.05, **p < 0.01).

The analysis of individual responses (Figure 7a) revealed noticeable inter‐individual variability of indentation depth at baseline, reflecting differences in initial skin mechanical properties among participants. Baseline values ranged from approximately 2.0 to 2.7 mm. Despite this variability, a clear pattern emerged over time. In the majority of participants, indentation depth decreased after repeated application of the hydrogel mask, particularly at weeks 2 and 4. This trend indicates an increase in skin resistance to mechanical deformation, corresponding to improved skin firmness. The magnitude of response varied between individuals. Participants with higher baseline indentation depth (indicating lower initial firmness) tended to show more pronounced reductions over time, while those with lower baseline values exhibited smaller changes. In some cases, partial reversal of the effect was observed at week 6, suggesting stabilization of the response rather than continuous improvement. The individual data indicate that the observed effect was present across most participants, although its magnitude varied between individuals. The distribution of indentation depth values (Figure 7b) confirms the trends observed at the individual level. A decrease in median values was observed after 2 weeks, with a more pronounced reduction at week 4, followed by partial stabilization at week 6. Statistical analysis indicated a time‐dependent effect. Although the Friedman test showed a trend toward significance (p = 0.094), exploratory pairwise comparisons using the Wilcoxon signed‐rank test indicated lower indentation depth values at week 4 (p = 0.0068) and week 6 (p = 0.0084) compared to baseline. Effect size analysis demonstrated a moderate effect (Kendall's W = 0.32), indicating a meaningful and consistent change in skin firmness over time. Responder analysis further supported these findings, with the majority of participants exhibiting decreased indentation depth during the study period. These results suggest that repeated application of the hydrogel formulation is associated with and improvement in skin firmness.

The analysis of Cutometer parameters (Figure 8a–d) provided additional insight into the mechanical behaviour of the skin.

The R0 parameter (Figure 8a), reflecting the extent of skin deformation under applied suction, showed a consistent decrease over time. This trend confirms the changes observed for indentation depth. A reduction in R0 values was observed after 2 weeks and was maintained at subsequent time points, indicating decreased skin deformability and increased mechanical resistance. Importantly, the values remained within the range typically reported for healthy facial skin (approximately 0.25–0.50 mm), suggesting that the observed changes reflect physiological modulation rather than abnormal skin behaviour [30]. Statistical analysis confirmed the significance of these changes, with all time points differing significantly from baseline (p < 0.05). The effect size was moderate (Kendall's W = 0.35), supporting the robustness of the observed trend. Responder analysis indicated that reduced R0 values were observed in the majority of participants throughout the study period. The strong agreement between R0 and Indentometer results confirms that the observed improvement in firmness is consistent across independent measurement techniques.

In contrast to firmness‐related parameters, elasticity‐related parameters (Figure 8b–d) demonstrated a more variable and less consistent response over time. R2 (overall elasticity) remained relatively stable over time, with no statistically significant changes observed. The values were within the expected range for adult skin (approximately 60–85%), indicating preservation of initial elastic properties. R5 (net elasticity) and R7 (elastic recovery) showed a non‐linear trend. A slight decrease was observed at early time points (weeks 2 and 4), followed by partial recovery or increase at week 6. For R5, the increase at week 6 reached statistical significance (p = 0.048), whereas R7 showed only a non‐significant trend. This behaviour may reflect transient changes in the viscoelastic properties of the stratum corneum. The initial decrease may be associated with hydration‐induced softening of superficial skin layers, leading to temporarily reduced elastic recovery [31]. With continued application, partial restoration and improvement of elasticity‐related parameters may occur, reflecting adaptation of the skin to repeated hydration.

The results demonstrate that the hydrogel formulation exerts a more pronounced and consistent effect on skin firmness than on elasticity‐related parameters. The improvement in firmness, confirmed by both Indentometer and R0 measurements, indicates increased resistance of the skin to mechanical deformation. These changes are consistent with the increase in skin hydration (see Section 3.2), suggesting that hydration‐related mechanisms play a key role in modulating mechanical properties. In addition to hydration‐driven effects, the presence of bioactive components in the formulation may contribute to extracellular matrix‐related cellular processes, thereby potentially supporting the observed improvement in skin firmness [32]. Importantly, these effects occurred without deterioration of skin barrier function (Section 3.3), indicating that the observed improvements in mechanical properties are achieved while maintaining skin homeostasis. The relatively modest and delayed response observed for elasticity‐related parameters is consistent with literature data indicating that changes in skin elasticity are typically associated with longer‐term extracellular matrix remodelling rather than short‐term physicochemical effects [33].

Effects on sebum level, skin colour and pH

To provide a broader characterization of skin responses to the hydrogel formulation, sebum level was assessed as an indicator of skin surface lipid balance during repeated application. Sebum measurements were performed on the forehead and cheek, reflecting regions with different physiological sebaceous activity. The results are presented in Figure 9 as median values with interquartile range together with individual data points.

FIGURE 9.

Changes in sebum level measured on the (a) forehead and (b) cheek during the 6‐week study period (median and interquartile range, n = 15). No statistically significant changes were observed (p > 0.05).

At the initial time point, sebum levels exhibited substantial inter‐individual variability, reflecting differences in skin type among participants. On the forehead, values ranged from approximately 45 to 180 μg/cm², whereas lower values were observed on the cheek (approximately 10–120 μg/cm²), consistent with the known distribution of sebaceous gland activity across facial regions. Throughout the study period, sebum levels showed moderate fluctuations; however, no consistent time‐dependent trend was observed for either measurement site. Importantly, the variability of values remained comparable across time points, indicating the absence of a systematic shift in sebum production.

This lack of a clear directional response indicates that the hydrogel formulation did not exert a strong modulatory effect on sebum production. Instead, the observed variability appears to reflect the inherent heterogeneity of sebaceous activity among individuals rather than a treatment‐related effect. Statistical analysis using the Friedman test confirmed that changes in sebum levels were not statistically significant for either the forehead or cheek (p > 0.05), supporting the observation that no consistent time‐dependent effect was present. From a physiological perspective, the maintenance of stable sebum levels suggests that the formulation does not disrupt skin surface lipid homeostasis [34]. The absence of excessive sebum reduction is also noteworthy, as overly aggressive lipid removal may impair barrier function and increase skin susceptibility to irritation. When considered alongside the increase in skin hydration (Section 3.2) and the maintenance of stable TEWL values (Section 3.3), these results indicate that the formulation improves skin hydration and mechanical properties without disrupting sebaceous homeostasis. These findings suggest that the formulation does not interfere with physiological lipid balance and supports the maintenance of skin homeostasis. Following the analysis of sebum levels, skin colour parameters were assessed to further evaluate changes in skin appearance, including brightness, redness and skin tone. The results are presented in Figure 10 for cheek and forehead, as median values with interquartile range together with individual data points (n = 15).

FIGURE 10.

Changes in skin colour parameters measured on the (a) cheek and (b) forehead at the initial time point and after 6 weeks of hydrogel mask application. Data are presented as median and interquartile range with individual values (n = 15). No statistically significant changes were observed (p > 0.05).

Skin colour parameters (L*, ITA°, b* and a*) measured before (the initial time point) and after 6 weeks of application showed only minor fluctuations, with no consistent time‐dependent trends observed across the study population. These parameters characterize skin brightness, redness and pigmentation‐related properties, where L* represents lightness, a* reflects erythema‐related changes, b* corresponds to the yellow‐blue axis, and ITA° characterizes skin tone and pigmentation.

At both measurement sites (cheek and forehead), L* values remained stable, indicating the absence of any noticeable skin‐brightening or darkening effect. Similarly, a* values, reflecting skin redness, did not show a systematic increase, indicating no evidence of erythema‐related changes. The b* parameter and ITA° values also remained within comparable ranges throughout the study period, confirming the absence of changes in skin tone and pigmentation. Importantly, the absence of increased redness—an explicit indicator of skin irritation—supports the good tolerability of the formulation, particularly in individuals with sensitive and allergy‐prone skin, as examined in this study [35].

This observation is consistent with previous reports indicating that stable or reduced erythema responses are associated with good dermatological tolerability of topical formulations, especially in sensitive skin conditions [36]. From a physiological perspective, the stability of skin colour parameters suggests that the hydrogel formulation does not induce visible alterations in skin appearance or disrupt pigmentation‐related processes. When considered alongside the stable sebum levels (Figure 9), unchanged TEWL (Section 3.3), and improved hydration and mechanical properties (Sections 3.2 and 3.4), these findings indicate that the formulation provides functional benefits without compromising skin appearance. Importantly, no visible adverse reactions or erythema‐related changes were observed.

Additionally, qualitative assessment of the skin surface was performed using high‐resolution imaging conducted on defined facial areas (forehead and cheek) at the initial time point and after 6 weeks of hydrogel mask application. Representative images of participants' skin are presented in Figure 11.

FIGURE 11.

Representative high‐resolution images of the skin surface obtained using Visioscope® PC 35, illustrating skin appearance at the initial time point and after 6 weeks of hydrogel mask application. No visible deterioration of skin surface structure was qualitatively observed. [Colour figure can be viewed at wileyonlinelibrary.com]

Qualitative analysis of the Visioscope images revealed no visible changes in skin surface topography or microrelief after 6 weeks of repeated hydrogel mask application. These observations are consistent with the instrumental measurements, confirming preservation of skin surface integrity and good tolerability of the formulation. No visible adverse reactions or erythema‐related changes were observed.

To complement the above findings, skin pH was evaluated as an additional parameter reflecting the acid–base balance of the skin surface, with the results presented in Figure 12.

FIGURE 12.

Changes in skin pH measured at the initial time point and after 6 weeks of hydrogel mask application (median and interquartile range, n = 15). Individual data points are shown. Differences were not statistically significant (Wilcoxon signed‐rank test, p > 0.05). [Colour figure can be viewed at wileyonlinelibrary.com]

Skin pH values decreased slightly from a median of 6.15 (IQR: 5.51–6.27) at baseline to 5.76 (IQR: 5.50–6.01) after 6 weeks of application. Although a trend toward lower pH values was observed, the change was not statistically significant (Wilcoxon signed‐rank test, p > 0.05). Importantly, pH values remained within the physiological range typical for healthy skin [37, 38].

The maintenance of physiological pH values suggests that the formulation does not disrupt the acid–base balance of the skin, which is essential for proper barrier function and microbial homeostasis. This is consistent with the use of mild and biocompatible formulation components that do not interfere with the natural acid mantle of the skin. A slight shift toward lower pH values may be considered beneficial, as mildly acidic conditions support enzymatic activity involved in barrier maintenance and inhibit the growth of pathogenic microorganisms. These experiments demonstrated that the hydrogel formulation preserves key parameters of skin homeostasis, including sebum production, colour and pH, without inducing measurable adverse changes.

In conclusion, the results presented in this section confirm that the formulation maintains the physicochemical and visual stability of the skin surface, supporting its suitability for repeated use, particularly in individuals with sensitive and allergy‐prone skin.

Subjective evaluation of the hydrogel mask

Subjective evaluation was conducted using a 7‐point Likert‐type scale ranging from −3 to +3, where −3 indicated a strongly negative perception, 0 a neutral response and + 3 a strongly positive perception, to assess user perception of the hydrogel mask, including comfort during use, ease of application, perceived immediate skin effect and mask assessment. The results are presented in Figure 13.

FIGURE 13.

Subjective assessment of the hydrogel mask, including comfort during application, ease of application, immediate skin effect and overall mask assessment (mean scores, −3 to +3 scale, n = 15). Higher values indicate more favourable responses. [Colour figure can be viewed at wileyonlinelibrary.com]

Participants consistently reported positive responses across all assessed parameters. Mean scores ranged from 2.17 to 2.67 on a scale from −3 to +3, indicating a strongly positive perception across all evaluated parameters. The highest ratings were observed for comfort during application and immediate skin effect (both 2.67), followed by overall mask assessment (2.50) and ease of application (2.17). All mean values were located in the upper positive range of the scale, with no neutral or negative trends observed. This indicates a high level of user acceptance and a consistently favourable perception of the hydrogel mask. Comfort during application was rated highly, which may be attributed to good adhesion of the hydrogel mask to the skin surface, its stable positioning without slipping, and the absence of excess liquid that could cause dripping or discomfort, particularly in sensitive facial areas such as the eyes. These features likely allowed participants to maintain normal activity (e.g. sitting or moving bearing the hydrogel mask) during application without disturbance. Ease of application received slightly lower, though still highly positive scores. This may reflect the inherent handling characteristics of hydrogel‐based formulations, which, despite providing good skin contact, may require careful positioning to ensure uniform adherence to facial contours. Immediate skin effect was also highly rated, indicating that participants perceived a rapid improvement in skin condition following application, likely associated with increased hydration and a transient smoothing effect on the skin surface.

No adverse sensations, such as burning, itching or discomfort, were reported during the study. This is consistent with the absence of irritation observed in the patch test and the stability of objective skin parameters, including TEWL, sebum level and skin colour. Subjective evaluation is thus consistent with the instrumental data, indicating that the hydrogel formulation provides measurable functional benefits while maintaining a favourable user experience. In summary, these findings further support the suitability of the formulation for repeated use, particularly in individuals with sensitive and allergy‐prone skin.

Short‐term skin response after application

Short‐term assessment was performed to evaluate the immediate skin response to hydrogel mask application and to provide additional insight into the mechanisms underlying the cumulative effects observed during repeated use. Therefore, selected skin parameters were monitored following a single application of the hydrogel mask. The assessment was performed in two individuals using a split‐face design, in which the hydrogel mask was applied to one side of the face, while the contralateral side remained untreated and served as a control. The results are presented in Figure 14a–d.

FIGURE 14.

Short‐term changes in skin parameters following hydrogel mask application (mean ± SD): (a) skin hydration, (b) transepidermal water loss (TEWL), (c) sebum level and (d) skin colour. [Colour figure can be viewed at wileyonlinelibrary.com]

The short‐term results demonstrate that hydrogel mask application induces a rapid but transient modulation of the skin microenvironment, primarily driven by occlusion and hydration‐related processes. However, short‐term hydration measurements also revealed noticeable fluctuations on the untreated control area during the 3.5 h observation period (Figure 14a), likely influenced by experimental conditions. This indicates that, under short‐term experimental conditions, skin hydration may vary dynamically even without product application, likely reflecting physiological variability, redistribution of water within the stratum corneum, and sensitivity of corneometric measurements to local skin conditions. During application, the hydrogel system created a hydrated and occlusive microenvironment in close contact with the skin surface. After mask removal, hydration values on the treated area did not remain elevated but gradually stabilized at values comparable to the initial level. However, in comparison with the untreated control area, a relative reduction in hydration was observed in the hydrogel‐treated skin during the observation period. This effect may reflect temporary hydration‐related changes in the superficial layers of the stratum corneum, potentially facilitate water evaporation after mask removal. This interpretation is further supported by the TEWL measurements (Figure 14b), which demonstrated increased transepidermal water loss in the treated area. Therefore, the short‐term hydration data should not be interpreted as evidence of a sustained immediate hydrating effect after a single application, but rather as indicating transient modulation of the skin surface microenvironment. This interpretation is consistent with the long‐term results, where significant improvement in hydration was observed only after repeated application over 6 weeks.

This transient hydration response was accompanied by dynamic changes in barrier‐related parameters, reflecting re‐equilibration of the stratum corneum after occlusion. In particular, TEWL increased shortly after mask removal (Figure 14b), suggesting enhanced water evaporation from the skin surface as the stratum corneum returned to its equilibrium state following occlusion. It should be noted that no additional emollient or occlusive product was applied after mask removal; therefore, the observed increase in TEWL and concurrent stabilization of hydration likely reflect natural post‐occlusion re‐equilibration processes associated with water evaporation from the skin surface. Importantly, TEWL values remained elevated throughout the short‐term observation period, indicating that the skin barrier had not fully returned to its baseline levels within the analysed timeframe. However, in the long‐term 6‐week study, no persistent increase in TEWL was observed, suggesting that repeated hydrogel mask application did not result in lasting impairment of skin barrier function.

Similar short‐term dynamics were observed for surface‐related parameters. Sebum levels also showed variability over time in both the treated and untreated areas (Figure 14c), indicating that short‐term sebum measurements are influenced by dynamic surface conditions and should be interpreted with caution. In the hydrogel‐treated area, sebum levels initially remained lower than or comparable to the initial value, which may be attributed to temporary occlusion‐related effects and redistribution of surface lipids during mask removal. At the final observation point, sebum values increased, suggesting recovery or redistribution of skin surface lipids rather than a persistent suppressive effect of the hydrogel mask. These findings support the interpretation that a single hydrogel mask application temporarily modifies skin surface conditions but does not induce a stable or directional change in sebum production [39].

Skin colour parameters also showed slight, transient changes (Figure 14d). An increase in L* values indicates a temporary enhancement of skin brightness, while a decrease in a* values suggests a reduction in redness, indicating no evidence of erythema‐related responses. Changes in ITA° values were consistent with a transient shift towards a lighter skin tone immediately after application. However, these effects diminished during the observation period, indicating a short‐lived cosmetic response without signs of irritation. The transient increase in hydration during application may also create favourable conditions for subsequent application of topical formulations.

When considered in the context of the dataset, these findings indicate that a single application of the hydrogel mask does not induce lasting changes in skin parameters but temporarily modifies the skin microenvironment. The short‐term variability observed in hydration and sebum levels, including fluctuations in the untreated control area, highlights the exploratory nature of this assessment and supports cautious interpretation of immediate effects. This transient modulation may contribute to increased water availability within the stratum corneum and may create favourable conditions for subsequent topical application, but the cumulative improvements observed in the long‐term study appear to require repeated use. Given the exploratory nature of this assessment and the limited number of participants, these observations should be interpreted with caution.

In vitro assessment of extracellular matrix protein synthesis

To further investigate the biological activity of the hydrogel formulation, its effect on extracellular matrix (ECM) protein synthesis was evaluated in human dermal fibroblasts. Fluorescence imaging was performed using the Col‐F probe, a fluorescent marker that selectively binds to collagen and elastin fibres in the extracellular matrix. The presence of these proteins is visualized as green fluorescence, with higher intensity corresponding to increased ECM protein content. Representative fluorescence images obtained after 48 h and 72 h of incubation are presented in Figure 15, and the quantitative analysis of fluorescence intensity is summarized in Figure 16.

FIGURE 15.

In vitro assessment of extracellular matrix protein synthesis in human dermal fibroblasts: Representative fluorescence images of collagen and elastin labelled with Col‐F probe (green fluorescence) after 48 h and 72 h of incubation. Control cells cultured in standard medium without additives are shown on the left, while cells exposed to hydrogel‐derived eluates are shown on the right. [Colour figure can be viewed at wileyonlinelibrary.com]

FIGURE 16.

Quantitative analysis of extracellular matrix (ECM) protein synthesis in human dermal fibroblasts exposed to hydrogel‐derived eluates after 24, 48 and 72 h of incubation. Fluorescence intensity (Col‐F staining) is expressed relative to control cells cultured in standard medium (set as 100%) and presented as mean ± SD (n = 8). Statistically significant differences are indicated as *p < 0.001. [Colour figure can be viewed at wileyonlinelibrary.com]

To enable direct comparison, fluorescence images include control fibroblasts cultured in standard medium without additives (left panels) and cells exposed to hydrogel‐derived eluates (right panels). Visual inspection of the representative images revealed a noticeable and reproducible increase in green fluorescence intensity in treated cells after 48 h and 72 h of incubation (Figure 15), indicating enhanced accumulation of collagen and elastin in the extracellular matrix compared to control conditions.

This qualitative observation was supported by quantitative fluorescence measurements, which were normalized to control cells (set as 100%). As shown in Figure 16, a progressive increase in fluorescence intensity was observed over time, confirming a time‐dependent increase in ECM protein content in response to hydrogel‐derived eluates. Statistical analysis using one‐way ANOVA indicated that the increase observed at 72 h was statistically significant compared to earlier time points (p < 0.05), while differences between 24 h and 48 h were not statistically significant.

Collagen and elastin are key components of the extracellular matrix and play an essential role in maintaining skin firmness, elasticity and structural integrity. Increased synthesis of these proteins is associated with improved mechanical properties of the skin and is considered a desirable outcome in cosmetic applications. The observed stimulation of ECM protein synthesis provides a potential biological basis for the changes in skin mechanical properties observed in vivo. In particular, the improvement in firmness‐related parameters (Indentometer and R0) and the progressive changes observed in elasticity‐related parameters (R5 and R7) may be associated with processes supporting extracellular matrix function. However, direct translation of in vitro findings to in vivo conditions is limited, and the observed effects should be interpreted as indicative rather than conclusive evidence of dermal remodelling. Nevertheless, the convergence of cellular responses and instrumental in vivo measurements supports the hypothesis that the hydrogel formulation may create conditions favourable for ECM‐related processes in the skin.

The observed biological activity may be attributed to the combined effect of the hydrogel matrix and incorporated active ingredients. The hydrated and occlusive environment created by the hydrogel system may facilitate the release and availability of bioactive compounds, enhancing their interaction with skin cells. In particular, components such as hyaluronic acid, ectoine, allantoin and tocopherol are known to support hydration, protect cellular structures and modulate cellular responses under stress conditions [40, 41]. Their presence in the formulation may contribute to the stimulation of fibroblast activity and the increased ECM protein synthesis observed in this study.

Therefore, the in vitro results demonstrate that the hydrogel formulation exhibits measurable biological activity at the cellular level, promoting the synthesis of key extracellular matrix proteins. When considered alongside the in vivo findings, these results support the concept that the formulation may improve skin condition through complementary physicochemical mechanisms (hydration and occlusion) and biologically relevant pathways associated with extracellular matrix function.

Study limitations

The present study has several limitations that should be noted when interpreting the results. The in vivo assessment was conducted in a relatively small pilot study group and followed an open‐label, baseline‐controlled design without a placebo or comparator formulation. The sample size (n = 15) may limit the statistical power to detect subtle differences and generalizability of the findings. In addition, although the short‐term study provided valuable mechanistic insight, it was performed on a limited number of participants and should be considered exploratory. Furthermore, the in vitro findings cannot be directly extrapolated to in vivo conditions and should be interpreted as supportive rather than definitive evidence of dermal‐level effects. Another limitation is the absence of long‐term follow‐up beyond the study period, which precludes assessment of the durability of the observed effects. Despite these limitations, the consistency observed across in vivo instrumental measurements, exploratory short‐term dynamic responses, and cellular‐level; responses provide complementary evidence supporting the interpretation of the formulation's effects.

CONCLUSIONS

The present study indicates that regular application of the hydrogel facial mask based on PVP, PEG‐400 and agar, and containing active compounds such as hyaluronic acid, ectoine, allantoin and tocopherol, is well tolerated by individuals with sensitive and allergy‐prone skin and provides measurable functional benefits under real‐use conditions. Six weeks of repeated use resulted in improved skin hydration and increased firmness, while barrier‐related parameters, sebum level, skin colour, skin surface appearance and pH remained unaltered. The absence of irritation in the patch test, together with stable TEWL values and no increase in erythema, indicates that the formulation does not compromise skin barrier function or visible skin tolerance. These findings are particularly relevant for sensitive skin, where efficacy must be balanced with the maintenance of skin homeostasis. The short‐term assessment showed that a single application induced transient changes in hydration, TEWL, sebum level and skin colour, consistent with temporary modulation of the skin microenvironment during and after hydrogel application. These effects support the interpretation that repeated use may lead to cumulative improvement in hydration‐related parameters rather than a persistent effect after a single application. In vitro experiments showed increased extracellular matrix protein synthesis in fibroblasts exposed to hydrogel‐derived eluates. These findings provide supportive evidence of biologically relevant cellular activity.

The observed effects may be attributed to both the physicochemical properties of the hydrogel matrix and the presence of bioactive components involved in hydration and barrier‐supporting processes. The formulation appears to act primarily through hydration‐ and occlusion‐related effects, with additional support from biologically relevant cellular responses. This integrated evaluation supports the suitability of the hydrogel mask for repeated use in the care of sensitive and allergy‐prone skin.

An additional advantage of the developed formulation is the use of radiation‐induced crosslinking technology originally established for the fabrication of medical hydrogel wound dressings. Besides enabling the formation of a resilient three‐dimensional polymer network, the applied radiation process simultaneously provides substantial reduction of bioburden, virtually to zero colony‐forming units (CFU) without the need for additional chemical crosslinking agents.

Equally important is the well‐defined composition of the hydrogel formulation. In contrast to many commercially available cosmetic products containing complex mixtures of stabilizers, emulsifiers, preservatives, fragrances, and other auxiliary additives that may contribute to irritation or sensitization, the presented hydrogel system is based on three well‐established hydrophilic polymers widely used in medical applications, combined with selected bioactive ingredients. Such a minimal and well‐defined composition is particularly advantageous for sensitive and allergy‐prone skin improving tolerability and reducing the risk of adverse skin reactions. Further studies involving larger cohorts and controlled clinical designs are warranted to confirm these findings.

FUNDING INFORMATION

This work was supported by European Regional Development Fund, RPLD.01.02.02‐10‐0008/19‐00.

CONFLICT OF INTEREST STATEMENT

B.R., A.A.‐W., A.K.O., R.C.‐B. and R.W. are affiliated with BioMatGel, a company involved in the development of hydrogel‐based formulations. The remaining authors declare no conflicts of interest.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.