Formulation of a Cannabinoid-, Prebiotic-, and Postbiotic-Based Face Serum—A 30-Day Pilot Study on Skin Hydration and Aging Parameters

Abstract

This study aimed to formulate and evaluate a facial serum containing Cannabis extract, a prebiotic blend of glycerin, lactitol, and xylitol, as well as heat-treated Lactobacillus plantarum HEAL19, a non-viable probiotic-derived ingredient (postbiotic) that preserves beneficial structural components and biological activity. Additionally, alternative preservatives were tested to replace conventional ones, aligning with environmentally and consumer-friendly cosmetic trends. The formulation underwent stability testing, physicochemical analysis, and microbiological control, including a challenge test to assess preservative efficacy. The efficacy of the formulation was investigated through a randomized, placebo-controlled pilot study involving sixteen healthy female volunteers aged 24–53 years. Participants were instructed to apply the active serum to one side of the face and the placebo preparation to the opposite side twice daily for a period of 30 days. Study endpoints were evaluated through clinical measurements of transepidermal water loss (TEWL), skin hydration, elasticity, and skin surface topography, together with participant-reported outcome questionnaires. Results demonstrated that the formulation possessed suitable physicochemical properties and microbiological stability. The serum was well tolerated and improved skin hydration. Participants reported enhanced esthetic appearance and perceived efficacy. These findings support the potential of combining innovative active ingredients with alternative preservatives in skin-friendly cosmetic formulations.

1. Introduction

The cosmetics industry is experiencing significant growth with the introduction of newer and advanced cosmetic products. Scientific documentation of the alleged bioactivity of new cosmetic ingredients, as well as guarantees relating to the safety of their use, is required [1,2]. Both these requirements are promoted both by legislation and by consumers themselves and are ensured by extensive studies of effectiveness, compatibility and toxicity. These studies concern both the product itself and its individual ingredients, with an emphasis on preservatives, as in the past, suspicions have been raised about their safe use [3].

The application of prebiotics, probiotics, and postbiotics in cosmetic formulations has attracted considerable scientific interest owing to their potential contribution to skin health and their role in regulating the composition and function of the skin microbiome. Prebiotics are particularly attractive for topical use, as they act as selective substrates that stimulate the growth and activity of beneficial skin microorganisms, thereby supporting barrier function, hydration, and overall skin homeostasis. In contrast, the use of live probiotics in cosmetics presents significant challenges, including formulation stability, preservation requirements, and maintaining microbial viability throughout the product’s shelf life. These limitations complicate their integration into conventional cosmetic systems. As a result, postbiotics—non-viable microbial cells or their bioactive components—have emerged as a promising alternative. Postbiotics retain many of the functional benefits of probiotics, such as anti-inflammatory and antioxidant properties, while offering improved stability, safety, and compatibility with standard cosmetic formulations. Consequently, they represent an innovative and practical approach for developing effective and microbiome-friendly skincare products [4].

Growing environmental concerns are also reflected in the search for new plant ingredients for local skincare applications. The related innovations that arise constitute a strong competitive factor in the cosmetic market [5]. Among the various plant ingredients that are systematically studied is cannabis. Cannabis-based products have been used mainly for pharmaceutical and medical purposes. In recent years, its use has been extended to the market of therapeutic and cosmetic personal care products. This extension was based on research related to the safety of the main active ingredient of cannabis, cannabidiol (CBD). These studies have shown positive results for its use in animals and in humans, while there are few reports of possible toxic effects [6,7,8,9,10].

The growing emphasis on environmental sustainability and health-conscious consumer behavior has led the cosmetic industry to reassess ingredient-selection strategies, particularly regarding substances for which safety concerns have been reported. Preservatives, in particular, have attracted considerable attention due to their potential association with adverse health effects. As a result, cosmetic manufacturers are increasingly exploring alternative preservative systems promoted as safer substitutes to conventional formulations; however, such claims should be supported by appropriate dermatological and safety evaluations [11,12].

The following article presents an experimental study in which the compatibility of the above three active ingredients within the same composition is investigated, while the addition of alternative preservatives is also investigated. The purpose of this research was to develop a Face Serum and assess the combined benefits of cannabinoids and prebiotics/postbiotics on women’s face skin (Figure 1). No prior research has been published that evaluates the combined effects of these three substances.

2. Materials and Methods

2.1. Cosmetic Ingredients Used for the Development of the Formulation

The selection of raw materials used for formulation development, including emollients, viscosity-adjusting agents, pH regulators, preservatives, and other excipients, was performed according to information provided in the corresponding Material Safety Data Sheets (MSDS). The developed formulation is hereafter referred to as the “Face Serum”.

Panthenol (Panthenol—BASF, Monheim am Rhein, Germany) represents the biologically active and chemically stable form of pantothenic acid (vitamin B5), which plays an essential role in cellular metabolic processes.

Glycerin (Glycerin—COSMOCHEM, Heraclion, Greece) is a natural ingredient found in all lipids of plant or animal origin. It is a powerful moisturizing and softening ingredient derived from natural sources or synthetic and widely utilized by the modern beauty industry [13].

Zemea^® (Propanediol— Primient Covation LLC, Loudon, TN, USA) is a natural, skin-friendly, preservative-enhancing alternative to oil-based glycols for manufacturers who want flexible and innovative cosmetic ingredients.

Hyaluronic acid—(Hyaluronic acid—Contipro, Dolní Dobrouč, Czech Republic) (HA) is a high-molecular-weight linear polysaccharide naturally found in the human body. It is a natural moisturizer for the skin, guaranteeing its elasticity and moisture retention properties.

Siligel^® (Xanthan Gum, Lecithin, Sclerotium Gum, Pullulan—Seppic, Paris, France) is a natural gel agent that leaves a feel of silicone on the skin. Siligel^® is easy to use (cold procedure, no pre-dispersion) and has high electrolyte tolerance (up to 20% NaCl), making it the ideal ingredient for preparations containing stress-causing ingredients. The versatility of Siligel^® leads to many applications as a gel, stabilizer, coagulant, suspension agent, or skin sensation enhancer as a silicone substitute, and it even has moisturizing properties. Its natural origin with a sustainable green production process meets today’s demand for ecological ingredients.

Covapearl Satin 931 (CI 77891, Mica—Sensient Cosmetic Technologies, Saint-Ouen-l’Aumône, France) is an inorganic marble pigment coated with titanium dioxide and rutyl. It appears as a white pearl powder with a satin shade.

For the selection of the active ingredients, the documentation and related efficacy studies were reviewed. SymReboot^® L19 (Maltodextrin, Lactobacillus Ferment- SYMRISE, Holzminden, Germany), Ecodermine^® (Glycerin, Lactitol, Xylitol- Lubrizol, Wickliffe, OH, USA), and Lipobelle^® Pino C (Pinus Cembra Wood Extract, Cannabis Sativa Seed Oil, Cannabis Sativa Leaf Extract, Lecithin, Alcohol, Pentylene Glycol, Tocopherol, Aqua/Water—Lubrizol, Wickliffe, OH, USA) were selected as active ingredients (

Table 1. Cosmetic claim depending on the three studied active ingredients used in the formulation.

Commercial Name	INCI Name	Cosmetic Claim
SymReboot® L19	Maltodextrin, Lactobacillus Ferment	Component based on probiotics for the care of sensitive skin. It is derived from a structurally preserved bacterium. By triggering the skin’s built-in defensive system, SymReboot® L19 helps to protect and soothe the skin barrier.
Ecodermine®	Glycerin, Lactitol, Xylitol	Protecting agent/Prebiotic. This composition consists of two complementary active ingredients dissolved in glycerin and is designed to support the maintenance and restoration of the cutaneous microflora and skin ecosystem. Its activity is associated with promoting microbial homeostasis within the skin microenvironment, thereby contributing to the reduction in disturbances related to microbial imbalance and supporting the skin’s natural defense mechanisms.
Lipobelle® Pino C	Pinus Cembra Wood Extract, Cannabis Sativa Seed Oil, Cannabis Sativa Leaf Extract, Lecithin, Alcohol, Pentylene Glycol, Tocopherol, Aqua/Water	It exhibits properties associated with the reduction in oxidative stress and discomfort sensation while also supporting tissue regeneration processes following injury and contributing to the relaxation of facial muscle tension. Additionally, it has been associated with improvements in skin appearance through reductions in parameters related to hemoglobin and melanin content, contributing to smoother skin texture in areas such as the cheeks, periocular region, and forehead. Lipobelle™ Pino C is a phytocomplex containing encapsulated cannabidiol (CBD).

).

Furthermore, replacing conventional preservatives with alternatives was considered so that the development of the products would keep pace with developments in the field of cosmetology for a shift to more environmentally friendly, as well as consumer-friendly, preservatives. Three preservatives were chosen: Nipaguard^® SCE (Sorbitan Caprylate, Propanediol, Benzoic Acid—Clariant, Muttenz, Switzerland), Euxyl^® PE 9010 (Phenoxyethanol, Ethylhexylglycerin—Schülke & Mayr, Norderstedt, Germany) and Iscaguard^® DGP (Pentylene Glycol, caprylyl glycol, decylene glycol—ISCA UK, Bromborough, UK). Stability and challenge tests were conducted for every product where each ingredient was used.

Placebo contained the same ingredients, at the same concentration as Face Serum (

Table 2. Analytical composition of Face Serum.

Commercial Name	INCI	Function	Supplier	INCI-KEY * (%)
Aqua	Water	solvent		A
Panthenol	Panthenol	moisturizing agent	BASF	E
Glycerine	Glycerin	denaturant/humectant/solvent	COSMOCHEM	E
Zemea®	Propanediol	denaturant/humectant/solvent	DuPont Tate & Lyle Bio Products/Primient Covation	D
Hyaluronic acid	Hyaluronic acid	humectant/skin conditioning/moisturizing	Contipro	F
Siligel®	Xanthan Gum, Lecithin, Sclerotium Gum, Pullulan	gelling agent	Seppic	E
Aqua	Water	solvent		D
SymReboot® L19	Maltodextrin, Lactobacillus Ferment	active ingredient/probiotic-based ingredient for sensitive skin care	SYMRISE	E
Ecodermine®	Glycerin, Lactitol, Xylitol	active ingredient/preservation and restoration of cutaneous microflora and ecosystem	Lubrizol	E
Lipobelle® Pino C	Pinus Cembra Wood Extract, Cannabis Sativa Seed Oil, Cannabis Sativa Leaf Extract, Lecithin, Alcohol, Pentylene Glycol, Tocopherol, Aqua/Water	active ingredient/phyto-complex with encapsulated cannabidiol (CBD)	Lipotec (Lubrizol)	E
Alcohol Denat.	Alcohol Denat.	solvent	Merck Group, Sigma-Aldrich	E
Parfum	Parfum	deodorant/masking	ELTON	F
Nipaguard® SCE or	Sorbitan Caprylate, Propanediol, Benzoic Acid	preservative	Clariant	E
Euxyl® PE 9010 or	Phenoxyethanol, Ethylhexylglycerin	preservative	Schülke & Mayr	F
Iscaguard® DGP	Pentylene Glycol, caprylyl glycol, decylene glycol	preservative	ISCA UK	E
Covapearl Satin 931	CI 77891, Mica		Sensient Cosmetic Technologies	F

* INCI Key A > 50%; 5% < D ≤ 10%; 1% < E ≤ 5%; 0.1% < F < 1%; G < 0.1%. Background colored: Three different preservatives were investigated in formulations of identical composition, differing only in the preservative system employed.

), with the three active ingredients being replaced by an equal concentration of aqua.

2.2. Assessment of the Developed Formulation’s Physical-Chemical and Microbiological Properties

Cosmetic products are routinely applied to sensitive regions of the body, often over prolonged periods, thereby rendering their safety a matter of significant importance. The safety profile of such products is influenced by multiple parameters, including their composition, formulation, and packaging. Product efficacy, in this context, is defined as the capacity to achieve the intended functional outcomes. The incorporation of appropriate excipients alongside carefully selected active ingredients can substantially enhance product performance, ensuring the fulfillment of its designated purpose. Regulation (EC) No. 1223/2009 highlights the importance of comprehensive safety evaluation procedures for cosmetic products while also defining key requirements associated with product efficacy, safety, and quality assurance.

To ensure conformity with this regulatory framework, a series of assessments was performed according to Regulation (EC) No. 1223/2009 of the European Parliament and of the Council (30 November 2009) concerning cosmetic products. The evaluation procedures included (i) formulation stability testing [14,15,16]; (ii) physicochemical characterization and organoleptic evaluation (including attributes such as color, odor, and visual appearance), as well as determination of density, pH, and viscosity [17,18]; and (iii) microbiological analysis to evaluate contamination levels and to determine preservative efficacy through challenge testing [19,20,21,22,23].

2.2.1. Testing the Cosmetic Formulation for Stability

For the accelerated stability study, the product was kept at 45 °C for 90 days.

2.2.2. The Cosmetic Formulation’s Quality Control

The following conclusions comprised the created formulation’s quality control: physicochemical control; viscosity (Brookfield DV-III Ultra, AMETEK Brookfield, Middleboro, MA, USA); pH; and organoleptic testing (appearance, color, and odor).

2.2.3. Assessment of Microbiological Quality and Preservative Performance of the Cosmetic Formulation

According to Regulation EU Regulation No. 1223/2009, cosmetic preservative systems must ensure both product stability and consumer safety throughout the product’s lifecycle while maintaining adequate preservation efficacy. The standard approach for demonstrating antimicrobial protection against microbiological contamination is Preservative Efficacy Testing (PET), also known as challenge testing. Cosmetic challenge testing procedures are performed in accordance with recognized industry standards, international guidelines, or pharmacopeial methods. The antimicrobial efficacy of the developed formulation was evaluated using standardized protocols according to ISO/IEC 17025:2017 [24], including the detection and enumeration of Staphylococcus aureus, Candida albicans, Escherichia coli, Pseudomonas aeruginosa, and Aspergillus brasiliensis [25].

2.3. Efficacy Assessment of the Cosmetic Formulation

Sixteen healthy participants with diverse skin types and ages ranging from 24 to 53 years took part in the study (Figure 2). The Face Serum being investigated and a placebo were applied in this trial. One side of each participant’s face was randomly assigned to receive the Face Serum, containing active ingredients, while the other side received the placebo. The treatment was continued for 30 days, with evaluations conducted in a double-blind manner. Throughout the study, the products were applied twice daily. Non-invasive biophysical assessments and a self-assessment questionnaire were employed to evaluate the effects. Specifically, measurements were taken for skin microtopography (using Skin Visioscan VC 98, Courage+Khazaka electronic GmbH, Cologne, Germany), transepidermal water loss (using the MPA5-Tewameter, Courage+Khazaka electronic GmbH, Cologne, Germany), keratin layer hydration (using the MPA5-Corneometer CM, Courage+Khazaka electronic GmbH, Cologne, Germany), and skin elasticity (using the Cutometer dual MPA 580, Courage+Khazaka electronic GmbH, Cologne, Germany). The findings of the research are summarized in the main conclusions, emphasizing the effectiveness of the products in enhancing skin quality.

Exclusion criteria comprised individuals receiving medical treatment, those using medications with the potential to influence study outcomes, participants with a documented history of hypersensitivity to cosmetic products, and individuals presenting with skin inflammation, infection, or other conditions that could interfere with the evaluation. Pregnancy was also considered a basis for exclusion. Throughout the study period, participants were instructed to refrain from the use of medications such as steroid-based hormone replacement therapies, oral contraceptives, and vitamin supplements.

At baseline, participants were advised to avoid applying the investigational cream for a minimum of twelve hours prior to assessment. Treatment allocation was performed by a team of pharmacists and chemists, who randomly assigned participants to one of two study groups. At the initial visit, coded containers—each containing 70 g of cream and lacking any indication of whether the formulation was active or placebo—were provided for twice-daily use. To ensure adherence and monitor product consumption, used containers were collected and assessed at each follow-up visit.

Skin parameters were assessed both before and after using the test product for 30 days (

Table 3. Evaluation protocol.

Evaluation Time	Qualitative and Quantitative Evaluations
D0	Instrument-based measurements of skin elasticity, hydration, transepidermal water loss (TEWL), and surface topography were performed prior to serum application. In parallel, a dermatological assessment was conducted to evaluate baseline skin condition.
D30	Instrument-based assessments of skin elasticity, hydration, transepidermal water loss (TEWL), and skin surface topography were conducted following 30 days of serum application. A dermatological evaluation of baseline skin condition was also performed. In addition, tolerability and any adverse events were monitored, along with a self-assessment questionnaire to gather user feedback.

). Before taking any measurements, the subjects had to wash their faces with a neutral lotion and be adjusted to the surrounding conditions for at least fifteen minutes (room temperature ranging between 19 and 21 °C and RH between 50 and 60%).

The following techniques were used to analyze in vivo skin parameters:

• Skin biomechanical characteristics were evaluated using the Cutometer^® Dual MPA 580 (Courage + Khazaka Electronic GmbH, Cologne (Köln), Germany). Elasticity measurements were obtained through the R5 and R7 parameters, where R5 reflects net elasticity (%), expressed as the ratio between elastic deformation during suction and immediate recovery during the relaxation phase (Ur/Ue), while R7 represents the percentage ratio of immediate recovery relative to total skin deformation following suction (Ur/Uf). Skin hydration measurements were performed using the Corneometer CM825^®, whereas transepidermal water loss (TEWL) was determined using the Tewameter TM300^®.
• Skin microtopographical characteristics were further examined using the Visioscan^® VC98 USB system (Courage + Khazaka Electronic GmbH). Surface characteristics were quantified according to Surface Evaluation of the Living Skin (SELS) parameters, including smoothness (SEsm), roughness (SEr), scaliness (SEsc), and wrinkle-associated parameters (Sew).

In addition, after 30 days of product use, the volunteers were given a self-evaluation questionnaire on day 0 before any application of the product; then self-assessment questionnaires were made available after the completion of 30 days after the application of the product [26].

2.4. Statistical Analysis

The variables were described using the mean value and the standard deviation or the mean and the interquartile range. Normality assumptions were evaluated using the Kolmogorov–Smirnov test.

The two-way ANOVA repeated measures model was used with factors “intervention” (between-group) and “time” (within group) to analyze the variables.

Baseline homogeneity between groups was assessed through sensitivity analyses of the evaluated variables. Changes from baseline to Day 30 were expressed as percentage change values, which were subsequently compared between interventions using paired t-tests or the Wilcoxon signed-rank test when data were not normally distributed. Statistical processing was conducted using IBM SPSS vr 21.00 Statistics software (IBM Corporation, Somers, NY, USA). All analyses were performed using two-tailed statistical tests, with statistical significance established at p < 0.05. Data obtained from self-assessment questionnaires were analyzed using Student’s t-test.

The Ethical Review Committee for Human Research approved this study, and research methods were followed when using human subjects in accordance with the Declaration of Helsinki. Prior to recruitment, all individuals provided informed permission (Research Ethics Committee, University of West Attica: 3349/16-01-2023, ClinicalTrials.gov Identifier: NCT07565922) [27].

3. Results

3.1. Quality Control Evaluation of the Face Serum Included Stability Studies, Physicochemical Characterization, and Microbiological Assessment

The developed formulation’s quality control, which involves the right physicochemical and pharmacotechnical properties (pH, viscosity), is a crucial study.

Table 4. Physicochemical characteristics of the Face Serum.

Test	Unit	Result
Viscosity at 20 °C (Brookfield DV-III Ultra)	cP	3500–4500
Density at 20 °C	g/cm3	1.00 ± 0.02
Appearance		Homogeneous *
Color		Light yellow
Odor		Specific
pH		5.0–5.3

* Nonmechanical impurities.

displays the findings of the physicochemical analyses performed on the created cosmetic formulation. The acquired results demonstrated the stability of the formulation under study and demonstrated a preparation with suitable physicochemical and pharmacotechnical properties, as well as an acceptable visual appearance (

Table 5. Stability testing of the Face Serum.

Time	t = 0	1st Month	2nd Month	3rd Month
TRIAL: S1—Euxyl pe 9010
Viscosity	4300	3170	3050	2750
pH	5.1	5.15	5.2	5.2
Color	Light yellow	Light yellow	Light yellow	Light yellow
TRIAL: S2—Nipaguard® SCE
Viscosity	3700	3100	2700	2500
pH	5.05	5.21	5.3	5.33
Color	Light yellow	Light yellow	Light yellow	Light yellow
TRIAL: S3—Iscaguard DGP
Viscosity	4100	3500	3250	3000
pH	5.01	5.1	5.15	5.2
Color	Light yellow	Light yellow	Light yellow	Light yellow

The viscosity measurement conditions were spindle size 3 and turns 10 rpm (maximum range 10,000 cP).

). The antimicrobial protection of the cosmetic formulation was demonstrated to be effective by the three conducted challenge tests (Euxyl PE 9010, Nipaguard^® SCE and Iscaguard DGP) meeting the A criteria (

Table 6. Microbial count expressed as CFU/g following the challenge test of Euxyl pe 9010.

TRIAL: S1—Euxyl pe 9010	Colony-Forming Units per Gram (CFU/g) After:
Test Organism	Baseline	7 Days	14 Days	28 Days	Criteria
Pseudomonas aeruginosa DSMZ 1128	4.30 × 105	<10	<10	<10	A
Staphylococcus aureus DSMZ 799	3.00 × 105	<10	<10	<10	A
Escherichia coli DSMZ 1576	5.00 × 105	<10	<10	<10	A
Candida albicans DSMZ 1386	1.30 × 105	<10	<10	<10	A
Aspergillus brasiliensis DSMZ 1988	9.00 × 104	ΝΤ	<10	<10	A

NT = Not Tested.

,

Table 7. Microbial count expressed as CFU/g following the challenge test of Nipaguard^® SCE.

TRIAL: S2—Nipaguard® SCE	Colony-Forming Units per Gram (CFU/g) After:
Test Organism	Baseline	7 Days	14 Days	28 Days	Criteria
Pseudomonas aeruginosa DSMZ 1128	4.30 × 105	<10	<10	<10	A
Staphylococcus aureus DSMZ 799	3.00 × 105	<10	<10	<10	A
Escherichia coli DSMZ 1576	5.00 × 105	<10	<10	<10	A
Candida albicans DSMZ 1386	1.30 × 105	<10	<10	<10	A
Aspergillus brasiliensis DSMZ 1988	9.00 × 104	ΝΤ	<10	<10	A

NT = Not Tested.

and

Table 8. Microbial count expressed as CFU/g following the challenge test of Iscaguard DGP.

TRIAL: S3—Iscaguard DGP	Colony-Forming Units per Gram (CFU/g) After:
Test Organism	Baseline	7 Days	14 Days	28 Days	Criteria
Pseudomonas aeruginosa DSMZ 1128	4.30 × 105	<10	<10	<10	A
Staphylococcus aureus DSMZ 799	3.00 × 105	<10	<10	<10	A
Escherichia coli DSMZ 1576	5.00 × 105	<10	<10	<10	A
Candida albicans DSMZ 1386	1.30 × 105	<10	<10	<10	A
Aspergillus brasiliensis DSMZ 1988	9.00 × 104	ΝΤ	<10	<10	A

NT = Not Tested.

). Nipaguard^® SCE and Iscaguard DGP could be equally good choices, but the preservative Iscaguard DGP was finally selected.

3.2. Biophysical Measurements

Measured values of R5 and R7 elasticity parameters, keratin hydration, transepidermal water loss, and skin topography at D0 and D30 are presented in

Table 9. The results of skin parameters.

Parameters	Face Serum		p-Value	%Variable	Placebo		p-Value	%Variable
	Baseline	30 Days			Baseline	30 Days
R5 ratio (high)	0.749 ± 0.314	0.558 ± 0.392	0.160	−36.29(113.3) (IQR)	0.718 ± 0.370	0.485 ± 0.354	0.021	−25.16(48.07) (IQR)
R5 ratio (low)	0.590 ± 0.270	0.255 ± 0.195	<0.005	−52.23% ± 37.10	0.494 ± 0.295	0.389 ± 0.312	0.286	−10.38% ± 51.45
R7 ratio (high)	0.478 ± 0.208	0.316 ± 0.183	0.034	−24.10(87.8)	0.469 ± 0.156	0.328 ± 0.125	<0.005	−31.13(34.2)
R7 ratio (low)	0.427 ± 0.171	0.194 ± 0.115	<0.005	−52.05(44.6)	0.341 ± 0.162	0.279 ± 0.137	0.287	−23.59(90.5)
Moisture level (hydration)	69.72 ± 15.93	76.25 ± 13.85	0.038	10.51% ± 24.92	64.66 ± 16.50	69.76 ± 16.04	0.177	11.41% ± 16.34
TEWL (g/h/m2)	13.68 ± 7.51	14.35 ± 8.31	0.784	−11.07(91.8)	15.14 ± 7.61	16.94 ± 6.21	0.106	6.45(45.26)
		SELS parameters
SEsm (high)	57.97 ± 11.68	60.8 ± 14.30	0.459	0.50(26.7)	65.43 ± 11.08	63.91 ± 15.05	0.754	−11.46(28.9)
SEsm (low)	48.61 ± 8.52	50.95 ± 9.86	0.322	5.26(26.1)	49.66 ± 7.26	50.68 ± 6.42	0.562	0.74(25.2)
SEr (high)	3.82 ± 1.00	4.21 ± 2.38	0.438	9.21% ± 45.96	3.94 ± 1.00	4.18 ± 2.01	0.664	8.87% ± 49.88
SEr (low)	3.05 ± 0.68	3.34 ± 1.60	0.499	1.85(60.2)	3.32 ± 1.58	0.382	−1.51(65.5)	2.86 ± 0.83
SEsc (high)	0.788 ± 0.275	0.791 ± 0.282	0.975	5.10(21.0)	0.815 ± 0.316	0.776 ± 0.265	0.681	−3.89(48.7)
SEsc (low)	0.644 ± 0.350	0.700 ± 0.200	0.614	15.23(65.1)	0.736 ± 0.273	0.679 ± 0.192	0.525	−5.00(54.8)
Sew (high)	50.65 ± 8.56	48.49 ± 9.13	0.431	−3.13(28.1)	49.60 ± 7.19	49.96 ± 9.17	0.885	2.77(30.7)
Sew (low)	42.99 ± 8.79	45.16 ± 9.26	0.355	6.86% ± 21.25	40.50 ± 5.38	43.56 ± 8.99	0.278	9.06% ± 25.10

Abbreviations: Statistical significance was defined as p-values < 0.05; IQR, interquartile range; R5 and R7, skin elasticity parameters; SEr, skin roughness; SEsc, skin scaliness; SEsm, skin smoothness; Sew, wrinkle parameter; TEWL, transepidermal water loss (g/h/m²).

. Mean percentage changes in the measurements are shown in Figure 3, Figure 4, Figure 5, Figure 6 and Figure 7.

3.2.1. Elasticity Index-R5

Within the Serum group, R5 High values did not show statistically significant modifications between baseline and day 30 (p = 0.160), whereas a significant variation was recorded in the Placebo group (p = 0.021). Baseline comparisons demonstrated comparable values between groups without statistically significant differences (p = 0.853). Likewise, comparison of percentage variation from baseline to day 30 revealed no statistically significant between-group differences for the R5 High index (p = 0.433).

For the R5 Low parameter, no statistically significant variation was observed in the Placebo group over the study period (p = 0.286). Although the Serum group exhibited lower values at day 30 compared with baseline, this reduction did not achieve statistical significance (p = 0.136). Comparative analysis at baseline demonstrated no significant differences between groups (p = 0.392) (Figure 3).

3.2.2. Elasticity Index-R7

A statistically significant modification in R7 High values during the intervention period was observed for both the Placebo group (p < 0.005) and the Serum group (p = 0.034). Initial comparisons confirmed the absence of statistically significant baseline differences between groups (p = 0.876). Similarly, the percentage variation in R7 High values from baseline to day 30 did not significantly differ between the two treatment conditions (p = 0.470).

No statistically significant differences in R7 Low values were detected within the Placebo group during follow-up (p = 0.287), whereas significant changes were identified in the Serum group (p < 0.005). Baseline assessment showed no statistically significant differences between groups (p = 0.125). In contrast, analysis of percentage changes from baseline to day 30 demonstrated statistically significant between-group differences for the R7 Low parameter (p = 0.006) (Figure 4 and Figure 5).

3.2.3. Keratin Hydration

Keratin hydration measurements demonstrated a statistically significant increase in the Serum group after 30 days of treatment (p = 0.038), while corresponding values in the Placebo group remained unchanged without statistical significance (p = 0.177).

Comparisons between treatment groups demonstrated statistically significant differences both before intervention (p = 0.034) and following 30 days of application (p < 0.005). However, evaluation of percentage changes throughout the intervention period revealed no statistically significant differences between groups (p = 0.868) (Figure 6).

3.2.4. Transepidermal Water Loss

Baseline TEWL measurements did not significantly differ between the two study groups (p = 0.086). Moreover, neither placebo-treated sites (p = 0.106) nor serum-treated sites (p = 0.784) demonstrated statistically significant TEWL modifications during the 30-day intervention period (Figure 7).

3.2.5. Skin Topography

Smoothness (SEsm)

No significant differences between groups were observed for baseline SEsm Low measurements (p = 0.597). Furthermore, assessment across the intervention period demonstrated no statistically significant alterations in either the Placebo group (p = 0.562) or the Serum group (p = 0.322).

Roughness (SEr)

Analysis of SEr High values revealed no statistically significant changes throughout the study period in either the Placebo group (p = 0.664) or the Serum group (p = 0.438). Similarly, no significant baseline differences between groups were identified (p = 0.720).

Evaluation of SEr Low measurements also failed to demonstrate statistically significant changes within the Placebo group (p = 0.382) or the Serum group (p = 0.499). Between-group comparisons at baseline additionally showed no statistically significant differences (p = 0.476).

Scaliness (SEsc)

Assessment of SEsc High values showed stability throughout the intervention period, with neither the Placebo group (p = 0.681) nor the Serum group (p = 0.875) exhibiting statistically significant changes. Baseline comparisons likewise indicated no statistically significant differences between groups (p = 0.490).

Similarly, analysis of SEsc Low measurements demonstrated no statistically significant variations during follow-up in either the Placebo group (p = 0.525) or the Serum group (p = 0.614). Baseline values also remained comparable between groups without statistically significant differences (p = 0.167).

Wrinkles (Sew)

Sew High values remained relatively stable throughout the study period, with no statistically significant changes identified in either the Placebo group (p = 0.885) or the Serum group (p = 0.431). Baseline comparisons revealed no significant between-group differences (p = 0.518).

Likewise, evaluation of Sew Low measurements demonstrated no statistically significant alterations in either study group during the intervention period (Placebo: p = 0.278; Serum: p = 0.355). Baseline comparisons similarly failed to demonstrate statistically significant differences between groups (p = 0.275).

3.2.6. Self-Assessment Questionnaire

Participant-reported outcomes collected at study completion suggested more favorable ratings for the active Face Serum compared with the placebo preparation. Additionally, subjects expressed positive perceptions regarding product texture and overall sensory attributes. The self-assessment questionnaire showed that the sense of clear improvement caused by the application of the Face Serum was 30.77% higher (p < 0.05) compared to the Placebo (Figure 7). Figure 3, Figure 4, Figure 5 and Figure 6 show the percentage change (%) over a 30-day period for the two compared groups—placebo and Face Serum—in the following four cases.

4. Discussion

In the present study, a novel dermocosmetic formulation was successfully developed through the combination of innovative bioactive ingredients, aiming to ensure physicochemical stability and microbiological safety. The increasing incorporation of plant-derived compounds, particularly cannabinoids, into cosmetic formulations reflects their emerging role as multifunctional ingredients with potential anti-inflammatory, antioxidant, and skin-barrier-modulating properties. These attributes make them particularly attractive for applications targeting sensitive and environmentally stressed skin.

Concurrently, advances in skin microbiome research have significantly influenced modern cosmetic science, emphasizing the importance of maintaining microbial balance for optimal skin health. Within this framework, prebiotics and probiotics have gained considerable attention as functional ingredients capable of modulating the skin ecosystem. Among probiotic strains, species belonging to the genus Lactobacillus are especially noteworthy due to their well-established safety profile, regulatory acceptance, and long history of use in both food and cosmetic applications. In recent years, the concept of postbiotics—non-viable microbial cells or their components that confer biological benefits—has further expanded formulation possibilities, offering enhanced stability while retaining bioactivity.

Based on these considerations, the present formulation incorporated three principal active components: (i) a cannabis-derived extract rich in bioactive phytochemicals, (ii) a heat-treated Lactobacillus-based postbiotic preserving structural integrity and biological functionality, and (iii) a prebiotic complex designed to support the growth and activity of beneficial skin microbiota. The integration of these ingredients into a serum-type formulation was achieved without compromising formulation stability. Comprehensive stability testing, including accelerated and real-time conditions, confirmed that the product maintained its physicochemical characteristics, such as pH, viscosity, and organoleptic properties, throughout its projected shelf life.

In parallel, a comparative assessment of preservation systems was conducted to ensure product safety while aligning with current trends toward milder and more sustainable preservatives. The study evaluated one conventional system, Schülke & Mayr’s Euxyl^® PE 9010, alongside two alternative preservative blends, Nipaguard^® SCE (Clariant, Muttenz, Switzerland) and Iscaguard^® DGP (ISCA UK, Bromborough, UK). All tested formulations successfully passed the preservative efficacy (challenge) test, demonstrating adequate antimicrobial protection against a broad spectrum of microorganisms. Despite comparable antimicrobial performance, Iscaguard^® DGP was ultimately selected due to its superior stability profile, as formulations containing Nipaguard^® SCE exhibited slight yellowing during storage, potentially affecting consumer acceptance.

The in vivo efficacy evaluation demonstrated that the active serum enhanced skin hydration following 30 days of regular application. More precisely, the Serum group showed a statistically significant change in the keratin hydration index from baseline to 30 days (10.51% ± 24.92 increase, p = 0.038), whereas the Placebo group did not show a significant change (p = 0.177). However, no statistically significant difference was observed in the percentage change from baseline to 30 days in the keratin hydration index between the groups (p = 0.868).

Measurements of skin elasticity parameters (R5 and R7) revealed a decrease in both treated and placebo sites. In particular, both the Placebo group (p < 0.005) and the Serum group (p = 0.034) showed a statistically significant change in the R7 High index from baseline to 30 days. However, there is no statistically significant difference between the groups at baseline (p = 0.876) nor at 30 days (p = 0.852). Additionally, there is no statistically significant difference in the percentage change from baseline to 30 days in the R7 High index between the groups (p = 0.470). The results suggest that the observed changes may be attributed to the effect of the formulation base or external or physiological factors rather than the direct action of the active ingredients within the relatively short study duration.

Furthermore, advanced skin imaging analysis did not reveal statistically significant alterations in overall surface topography; however, a trend toward improvement in wrinkle appearance, as reflected by the Sew parameter (−3.13%), and enhanced skin smoothness (+5.26%) was observed in areas treated with the active formulation.

Importantly, the product demonstrated an excellent safety profile, as no adverse reactions or signs of irritation were reported throughout the study period. Subjective evaluations further supported these findings, with participants reporting high levels of satisfaction and perceived improvements in skin hydration, comfort, and overall appearance.

Taken together, these results highlight the potential of the developed formulation as a safe, stable, moisturizing dermocosmetic product combining benefits of cannabinoids, postbiotics, and prebiotics. Nevertheless, further investigations involving different concentrations of active compounds, larger study populations, extended treatment durations, and post-treatment follow-up are warranted to fully elucidate the long-term efficacy, durability of effects, and potential cumulative benefits associated with continued use.

5. Conclusions

In conclusion, the combination of three active ingredients—(a) cannabis extract, (b) a processed probiotic retaining structural and functional activity, and (c) a prebiotic blend—proved to be a safe and promising skincare approach aligned with current cosmetic trends. The formulation, developed using a non-conventional preservative system, demonstrated improved skin hydration and resulted in higher participant-rated esthetic outcomes compared with the untreated condition. This pilot study provides preliminary evidence supporting the beneficial effects of the developed facial serum on skin condition and appearance, thereby justifying further investigation in larger, well-controlled clinical studies. Future research should address the limitations of the present study and further evaluate the long-term effects of the formulation across broader and more diverse populations to support its applicability in the global skincare market.