Cosmetic preparation comprising anisic acid and levulinic acid with selective antimicrobial activity

Abstract

The present invention relates to cosmetic and dermatological preparations comprising a combination of levulinic acid and anisic acid. These preparations are particularly suitable for use on the skin. They have a selective antibacterial effect on the skin, specifically controlling anaerobic bacteria in the skin flora, with little or no bactericidal effect on aerobic bacteria. Consequently, the preparations are suitable for cosmetic skin care and for the dermatological treatment of certain skin conditions, such as acne.

Description

[0001] The invention relates to cosmetic and dermatological preparations comprising a combination of levulinic acid and anisic acid. The preparations according to the invention are particularly suitable for application to the skin. The preparations exhibit a selective antibacterial effect on the skin by specifically targeting anaerobic bacteria of the species Cutibacterium acnes combat the skin flora, while having little or no bactericidal effect against aerobic bacteria of the species S. epidermidis The compositions according to the invention are therefore suitable for cosmetic skin care as well as for the dermatological treatment of certain skin diseases, such as acne. HINTERGRUND DER ERFINDUNG

[0002] The microbiome of human skin is a complex mixture of different groups of microorganisms: anaerobic bacteria, such as Cutibacterium acnes ( C. acnes ), colonize the skin in close proximity to aerobic bacteria, such as Staphylococcus epidermidis (S. epidermidis) and Staphylococcus hominis ( S. hominis ) as well as mushrooms.

[0003] It is known that the interactions between S. epidermidis and C . acnes is of particular importance for skin health. S. epidermidis is an aerobic, spherical, gram-positive bacterium that is catalase-positive and coagulase-negative. C . acnes This is an anaerobic, gram-positive bacterium. It is believed that both microorganisms exist on healthy skin in a relatively stable equilibrium, and that a disruption of this balance, known as dysbiosis, can negatively affect the skin's condition by triggering or at least promoting skin blemishes or even skin diseases. Therefore, for the treatment or prevention of such blemishes or skin diseases, it is of particular importance to provide agents that restore the ratio of anaerobic to anaerobic microorganisms in the skin flora, and especially the ratio of S . epidermidis and C. acnes, can be specifically altered. This is particularly important because it can lead to increased growth of anaerobic bacteria, such as... C . acnes, Since this can be associated with the development of skin diseases, preparations that are selectively effective against anaerobic bacteria are particularly needed.

[0004] Anisic acid is a methoxylated benzoic acid (4-methoxybenzoic acid) that has bacteriostatic properties and is also attributed with anti-inflammatory and fungicidal effects. Anisic acid is used, among other things, as a preservative in cosmetic products to prevent contamination by bacteria or fungi. For this purpose, anisic acid is added to these products in a concentration of 0.05–0.3%.

[0005] Levulinic acid, also known as 4-oxopentanoic acid or 4-oxovaleric acid, is a chemical compound belonging to the γ-keto acids. Internationally declared as "levulinic acid," this acid and its salts are in demand in the field of skincare, primarily as a fragrance additive, due to their characteristic scent reminiscent of caramel or vanilla. Levulinic acid is also known for its antibacterial and antifungal properties. This makes it an attractive skincare ingredient for blemished skin. Since levulinic acid is not declared as a preservative, it is ideally suited for preserving natural cosmetics. The use of levulinic acid as a preservative in cosmetic products has been well documented, with the substance being added to the products to be preserved in a quantity of 0.3–1.0%.

[0006] Preservatives are regularly used in cosmetics to protect the product from contamination by bacteria and fungi. The microbiological stability of cosmetics is a crucial factor for shelf life and consumer health protection. In the European Cosmetics Regulation, preservatives are defined as substances used exclusively or predominantly to inhibit the growth of microorganisms in cosmetic products. The substances permitted for this purpose are listed in the corresponding positive list in Annex V of the EU Cosmetics Regulation.

[0007] The use of anisic acid and levulinic acid as preservatives has been described in the prior art. EP 1 541 124 A2 describes a synergistic effect between two active ingredients used for preservation, namely anisic acid and C6-14 fatty acid monoglycerides. The mixture is said to exhibit antimicrobial activity that can be used to preserve cosmetic formulations. The resulting formulations thus contain a broad-spectrum antimicrobial agent with good skin compatibility. EP 2 735 301 A1 discloses the combination of levulinic acid, the sodium salt of levulinic acid (sodium levulinate), and anisic acid for preserving a cosmetic product.

[0008] US 2003 / 147930 A1 describes cosmetic preparations containing levulinic acid that are used in the treatment of skin problems.

[0009] KR 2013 0136332 A discloses a preservative containing levulinic acid and anisic acid, which is used in cosmetics.

[0010] CN 109 157 505 A describes a gel with antibacterial properties, containing a combination of anisic and levulinic acid, and applied topically to the vaginal mucosa.

[0011] While anisic acid and levulinic acid have proven effective in preserving cosmetic products, their use for targeted modification of the skin flora is not yet known. As explained above, there is a need for cosmetic and dermatological formulations that contribute to improving the overall condition and health of the skin by specifically influencing the composition of the skin flora. At the same time, these formulations should exhibit good skin compatibility. BESCHREIBUNG DER ERFINDUNG

[0012] The present invention is based on the surprising finding that anisic acid in combination with levulinic acid can be used to selectively reduce the concentration of anaerobic bacteria in the skin flora, in particular C. acnes, to reduce. The invention therefore relates to the use of a combination of anisic acid and levulinic acid for the reduction of anaerobic bacteria of the species Cutibacterium acnes and simultaneous preservation of aerobic bacteria of the species S. epidermidis on the skin. This combination allows for a selective antibacterial effect to develop on the skin after application.

[0013] The present disclosure concerns a composition for the targeted modification of the skin flora, the composition comprising the following: (i) anisic acid or an antimicrobial salt thereof, and (ii) levulinic acid or an antimicrobial salt thereof.

[0014] The compositions preferably contain anisic acid. However, salts of anisic acid can also be used, provided they exhibit sufficient antimicrobial activity. Salts of anisic acid suitable for use within the scope of the present invention preferably have antimicrobial activity that is at least 50% of the activity of anisic acid in a corresponding in vitro assay. This means that when using equal amounts of anisic acid and the salt of anisic acid to determine the antimicrobial activity in an in vitro assay, the salt of anisic acid must have at least half the antimicrobial activity of anisic acid. Suitable salts for use within the scope of the present invention are sodium and potassium anisate.

[0015] Suitable salts of levulinic acid for use in the present invention preferably exhibit antimicrobial activity that is at least 50% of the activity of levulinic acid in a corresponding in vitro assay. This means that when using equal amounts of levulinic acid and the salt of levulinic acid to determine the antimicrobial activity in an in vitro assay, the salt of levulinic acid must exhibit at least half the antimicrobial activity of levulinic acid. Suitable salts for use in the present invention are sodium and potassium levulinate.

[0016] In particular, a composition for the targeted modification of the skin flora is disclosed, the composition of which (i) more than 0.3% (w / w) anisic acid or an antimicrobial salt thereof, and (ii) more than 1.0% (w / w) levulinic acid or an antimicrobial salt thereof.

[0017] In a particularly preferred embodiment, the composition comprises at least 0.5% (w / w) anisic acid or an antimicrobially active salt thereof, and at least 1.5% (w / w) levulinic acid or an antimicrobially active salt thereof. The amount of anisic acid or the anisic acid salt in the composition is preferably at least 0.75%, at least 1.0%, at least 1.5%, at least 2.0%, at least 2.5%, at least 3.0%, at least 3.5%, at least 4.5%, or at least 5.0% (w / w). The amount of levulinic acid or the levulinic acid salt in the composition is preferably at least 2.0%, at least 2.5%, at least 3.0%, at least 3.5%, at least 4.5%, or at least 5.0% (w / w).

[0018] In other words, the composition disclosed herein preferably comprises between 0.5 and 5.0% (w / w) anisic acid or an antimicrobially active salt thereof, and between 1.5 and 5.0% (w / w) levulinic acid or an antimicrobially active salt thereof. A composition comprising between 1.0 and 4.0% (w / w) anisic acid or anisic acid salt and between 2.0 and 4.0% (w / w) levulinic acid or levulinic acid salt is particularly preferred. A composition comprising between 1.5 and 3.0% (w / w) anisic acid or anisic acid salt and between 2.0 and 3.0% (w / w) levulinic acid or levulinic acid salt is even more preferred. Even more preferred is a composition comprising between 2.0 and 3.0% (w / w) anisic acid or anisic acid salt and between 2.5 and 3.0% (w / w) levulinic acid or levulinic acid salt.

[0019] The compositions disclosed herein can be presented as a single formulation or as components that are combined immediately before application to the skin. In the latter case, the above quantities apply to the composition resulting from the combination of components immediately before application. Also disclosed are compositions in which the two antimicrobial components, namely anisic acid or its salt and levulinic acid or its salt, are presented as separate formulations that are applied to the skin sequentially. Thus, the two antimicrobial components can be applied to the skin at intervals of approximately 5, 10, 15, 20, 24, or 30 minutes.

[0020] The compositions disclosed herein can be in various forms. For example, a solution, a suspension, a water-in-oil (W / O) or oil-in-water (O / W) emulsion, or a multiple emulsion, such as a water-in-oil-in-water (W / O / W) or oil-in-water-in-oil (O / W / O) emulsion, a hydrodispersion or lipodispersion, or even an aerosol are preferred preparation forms. Preferably, the composition disclosed herein is in the form of emulsions containing, in addition to the antimicrobial components, other substances such as fats, oils, waxes, and / or other fatty substances, as well as water and one or more emulsifiers, such as those commonly used for this type of formulation. Such emulsions can advantageously be formulated as a cream or lotion. Furthermore, it is also possible and advantageous to incorporate the combinations of anisic acid and levulinic acid into aqueous systems or...To introduce surfactant preparations for cleaning the skin and / or hair.

[0021] It is of course known to those skilled in the art that cosmetic and therapeutic compositions are generally inconceivable without the usual excipients and additives. These include, for example, consistency enhancers, fillers, fragrances, colorants, emulsifiers, additional active ingredients such as vitamins or proteins, sunscreens, stabilizers, insect repellents, alcohol, water, salts, as well as antimicrobial, proteolytic, or keratolytic substances, etc., provided that their use does not significantly inhibit or otherwise contradict the antimicrobial activity of the combination disclosed herein.

[0022] The combinations of anisic acid and levulinic acid disclosed herein can be advantageously incorporated into conventional cosmetic and dermatological preparations, which in turn can be in various forms. The compositions can be, for example, creams, lotions, gels, ointments, pastes, or solid sticks.

[0023] The compositions described above are particularly suitable for the non-therapeutic, cosmetic, and / or therapeutic treatment of the skin, especially facial skin. In a particular embodiment, the invention relates to a composition as described above for use in a method for treating a skin disease. The skin disease is preferably dermatitis. The treatment of acne (Acne vulgaris) The compositions described above are particularly preferred. The therapeutic effect of the compositions advantageously results from the targeted modification of the concentration of anaerobic bacteria of the species. Cutibacterium acnes on the skin. The concentration of these anaerobic bacteria is reduced, with the concentration of anaerobic bacteria of the species S. epidermidis in the same habitat is not reduced, or not significantly reduced. This results in a shift in the ratio of C. acnes to S. epidermidis.

[0024] The compositions disclosed herein are also suitable for non-therapeutic, cosmetic use. Such non-therapeutic, cosmetic use can serve to selectively reduce the number of anaerobic bacteria on the skin, and in particular the selective reduction of the number C. acnes. In this way, skin impurities can be eliminated or prevented. In particular, blockages of sebaceous glands, such as those that occur in comedones, can be avoided. The non-therapeutic, cosmetic use can thus significantly improve the visual appearance of the skin. In another embodiment, the invention also relates to the non-therapeutic use of a composition of the preparation as defined above for skin care in cases of acne.

[0025] The compositions can be applied to the skin once or multiple times as part of therapeutic or non-therapeutic, cosmetic treatment. In one embodiment, the compositions disclosed herein are formulated for daily application to the skin. In an alternative embodiment, the compositions disclosed herein are formulated for single application to the skin. Surprisingly, the combination of anisic acid and levulinic acid in the compositions acts selectively, i.e., it targets the anaerobic bacteria of the species. C. acnes are reduced on the skin and the aerobic bacteria of the species S. epidermidis are not attacked, or not significantly.

[0026] The advantage of the compositions disclosed here lies in their high antimicrobial selectivity. These compositions specifically lead to a significant reduction in the cell count of anaerobic bacteria of the species. C. acnes, which colonize the skin. At the same time, the compositions have no or only a minimal inhibitory effect on aerobic bacteria of the species. S. epidermidis, whose numbers on the skin are not significantly reduced. As explained in the examples described below and shown in Figures 1-2, the use of the compositions disclosed herein leads to a 90% reduction in anaerobic bacteria, while aerobic bacteria actually continue to multiply during the period studied.

[0027] It is preferred that the number of anaerobic bacteria in a specific skin area decreases by at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% after application of the composition, compared to the cell count in the relevant skin area before application. It is further preferred that the number of aerobic bacteria in this skin area simultaneously decreases by at most 25%, at most 20%, at most 15%, at most 10%, at most 5%, or less, compared to the cell count in the relevant skin area before application of the composition.

[0028] It is particularly preferred in the present case that the number of C. acnes in a specific skin area, after application of the composition, the number of cells in that area decreases by at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% compared to the cell count in that skin area before application. It is also preferred that the number of S. epidermidis in this skin area, the number of cells decreases by no more than 25%, no more than 20%, no more than 15%, no more than 10%, no more than 5% or less compared to the cell count in the skin area in question before application of the composition.

[0029] The efficacy of the formulations has been demonstrated in various studies, which are described in the following examples. In one test, bacteria were collected from the cheek using a swab technique and incubated aerobically and anaerobically (i.e., at reduced oxygen levels). After 14 days of application, bacteria were again collected from the subjects. Analysis of all the data revealed a surprising result. No abnormalities were observed in the aerobically cultured bacteria, while the anaerobically cultured bacteria showed a significant reduction of more than 90% in bacterial cell count after just one week. This selective behavior was confirmed in further in vitro studies. BEISPIELE

[0030] The following examples are intended to illustrate the present invention without limiting it. Unless otherwise stated, all quantities, proportions, and percentages are based on the weight and total quantity or total weight of the respective preparations and compositions. Beispiel 1: Production of bacterial suspensions and growth experiments

[0031] S. epidermidis (DSM 1798) was extracted from a cryovial (EN 12353), streaked onto a CASO agar plate, and incubated at 37°C for 24 h. A second incubation was then performed. This second incubation was inoculated with 10 ml of BHI medium and 5 g of glass beads (4 mm diameter) and shaken for 3 min. The solution was then adjusted to an OD600 of 0.1 and subsequently diluted 1:10 with diluent. This bacterial suspension was then used for the growth assay. Test - Growth experiment with S. epidermidis

[0032] 10 µL of bacterial suspension was added to each well of a 24-well plate and allowed to dry completely (at least 45 min under a sterile workbench). After drying, 10 mg of the formulation under investigation (see Table 1) was pipetted and distributed into the well using a T-spatula. The control remained untreated. The plate was stored uncovered in a humid incubator at 37°C and 90% relative humidity for the incubation period (6 h / 24 h). After the incubation period, 500 µL of rinsing buffer was added to each well and rinsed in an ultrasonic bath for 1 min. 100 µL of the resulting supernatant was added to 900 µL of neutralizing agent and then plated onto CASO agar using a spiral plater. The agar plates were incubated at 37°C for 24 h, and the colonies were subsequently counted using the I+L Countermat.

[0033] C. acnes (DSM 1897) was streaked from a cryovial (EN 12353) onto an agar plate (COST agar) and incubated at 37°C for 5 days in an anaerobic box. This culture was then used to inoculate 10 ml of anaerobic medium in a CELLSTAR CELLreactor tube and incubated for 18 hours in an anaerobic box. This culture was then adjusted to an OD600 of 0.5 and subsequently diluted 1:10 with anaerobic medium. This bacterial suspension was then used for the growth assay. Test - Growth experiment with C. acnes

[0034] 10 µL of bacterial suspension was added to each well of a 24-well plate and allowed to dry completely (at least 45 min under a sterile workbench). After drying, 10 mg of the formulation under investigation (see Table 1) was pipetted and distributed into the well using a T-spatula. The control remained untreated. The plate was incubated uncovered in an anaerobic box (lined with cellulose + 50 mL of water) at 37°C for the incubation period (6 h / 24 h). After the incubation period, 500 µL of rinse buffer was added to each well and rinsed in an ultrasonic bath for 1 min. 100 µL of the resulting supernatant was added to 900 µL of neutralizing agent and then plated onto COST agar using a spiral plater. The agar plates were incubated at 37°C for 5 days, and the colonies were subsequently counted using the I+L Countermat.

[0035] The reduction factor was determined as part of the analysis. The reduction factor is the factor by which the cell count (CFU) at different time points is reduced compared to the T0 control or to each other. CFU Kontrolle CFU Testsubstanz = Reduktionsfaktor

[0036] The study design is such that the antibacterial efficacy of the test formulations is demonstrated by comparison to the untreated control. Tabelle 1: tested formulations and results of the growth trials Formulierung Nr. 1 2 3 4 5 6 INCI % % % % % % p-Anisic Acid 0,1 0,1 0,1 0,1 0,1 0,1 Levulinic Acid (Aqua / Glycerin / Sodium Levulinate) 0,5 0,5 0,5 0,5 0,5 0,5 Glycerin + Arctium Lappa Fruit Extract 1,2 1,2 1,2 0 0 0 Ethylhexylglycerin 0,1 0,1 0 0,1 0,2 0,1 Decylene Glycol 0 0,1 0,1 0,1 0 0 Sodium Hyaluronate + Aqua 0 0 0,1 0 0 0 Maltodextrin + Chamomilla Recutita Flower Extract 0 0 0 0,6 0 0 Dicaprylyl Ether 2,8 3,5 0 3,5 2,8 2,8 Simmondsia Chinensis Seed Oil 3,5 3,5 0 3,5 3,5 3,5 Butyrospermum Parkii Butter 2 2 0 2 3,5 2 Prunus Amygdalus Dulcis Oil 3 3,5 0 3,5 5 3 Coco-Caprylate / Caprate 1,2 0 0 0 0 1,2 Argania Spinosa Kernel Oil 0,1 0,1 0,1 0 0,1 0 Caprylic / Capric Triglyceride 0 1 0 1 0 0 Brassica Campestris Seed Oil 0 0 6 0 0 0 Glyceryl Stearate 2 2 0 2 2 2 Glyceryl Caprylate 0,3 0,3 0,3 0,3 0,3 0,3 Sodium Stearoyl Glutamate 0,3 0,3 0 0,3 0,3 0,3 Sodium Cetearyl Sulfate 0 0 0,2 0 0 0 Perfume 0,35 0,35 0,35 0 0,3 0,3 Glycerin 8,4 8,4 9 8,4 8,4 8,4 Cetearyl Alcohol 5 5 0 5 5 5 Xanthan gum 0,3 0,3 0,2 0,3 0,3 0,3 Cetyl Alcohol 0 0 3 0 0 0 Hydroxypropyl Starch Phosphate + Aqua 0 0 3 0 0 0 Alcohol Denat. + Aqua 4 4 4 4 4 4 Aqua ad 100 ad 100 ad 100 ad 100 ad 100 ad 100 Reduction factors 1 2 3 4 5 6 Staphylococcus epidermidis after 6 hours 1 1 10 1 1 1 Cutibacterium acnes after 6 hours 40 134 1651 214 813 71

[0037] The count showed that the number of aerobic S. epidermidis Bacteria were not affected, or not significantly affected, by the formulation containing anisic acid and levulinic acid. In the approaches of S. epidermidis Only small reduction factors were measured. In contrast, the number of anaerobic C. acnes Bacteria are significantly reduced by the formulations. Example 2: ATA test

[0038] The ATA test is used to determine the antibacterial efficacy of cosmetic formulations after twice-daily application. The test duration is typically one week. The test formulation is applied and its efficacy is measured on the consumer-relevant area, the cheek. The target parameter is the count of aerobic and anaerobic bacteria.

[0039] All subjects underwent a 3-day preconditioning period using a prescribed wash gel. After rinsing the cheeks, the "Test Formulation 5" described in Table 1 was applied according to instructions. A swab was then taken using a Floq Swab. Three sets of 10 strokes were applied to a 5 cm x 5 cm area of ​​the cheek in a defined pattern. The swab pattern is shown in Figure 3The procedure is described below. During the sampling cycles, the Floq swab is soaked in a rinsing buffer, and after the third sampling, the swab remains in the rinsing buffer. The solution is diluted directly, and each sample is plated onto two agar plates using a spiral plater. The swabbing is then repeated at predetermined intervals, usually after one week. Finally, half of the agar plates were incubated at 37°C for 5 days in the absence of oxygen, and the other half were incubated at 37°C for 24 hours. Subsequently, the agar plates were analyzed using the Countermat.

[0040] The results of the ATA test are shown in Figures 1 and 2. Figure 1This shows the results of the anaerobic cultivation. It can be seen that the cell count of the anaerobic bacteria decreased significantly after treatment with the test formulation containing a combination of anisic acid and levulinic acid. Such a reduction in cell count is not observed in Figure 2 The results of aerobic cultivation were not discernible. In fact, an increase in cell count was observed. Figures 1 and 2 thus impressively demonstrate the selective efficacy of the combination of anisic acid and levulinic acid disclosed here. Example 3: Suspension tests

[0041] The effect of the formulations disclosed herein was demonstrated in suspension tests with S. epidermidis and C. acnes further investigations. Glycerol stock cultures of S. epidermidis (DSM 1798) and C. acnes(DSM 1897), which had been prepared according to European standard 12353, were stored in a refrigerator at 5°C. A first passage was prepared from these liquid stock cultures. For this, the appropriate culture was transferred to an agar plate using a sterile single-use inoculation loop ( C. acnes: COST agar, S. epidermidis: The cultures of C were streaked onto COAST agar and then incubated. . acnes were incubated for 5 days at 37°C, while the cultures of S. epidermidis The colonies were incubated for 24 hours at 37°C. A second agar passage was then prepared from this first passage by collecting a few colonies with a sterile single-use inoculation loop and streaking them onto a new agar plate. This second passage was then incubated for 5 days (24 hours) at the appropriate temperature. The resulting second passage was then used for the suspension test.

[0042] To prepare the suspensions, a few colonies from the second passage were collected using a sterile inoculation loop and added to 10 mL of medium in a baffle-shaped flask containing 5 g of glass beads (Ø 4 mm) and gently shaken for 3 minutes. The approximate cell count per mL was then adjusted using optical density (OD). The optical density was determined using an Eppendorf photometer at 600 nm. The resulting OD was adjusted to a value of approximately 0.8 (±0.01) and then diluted again 1:50. This dilution strategy yielded a cell count of approximately 1 x 10⁶ < 1.

[0043] For the test formulations, 50µL of the antimicrobial raw material solution and 450µL of medium were placed in sterilized Eppendorf reaction vessels ( C. acnes: Anaerobic medium, S. epidermidis:BHI medium). For the positive control, 500 µL of medium was used. After adding 500 µL of the prepared culture suspension, 1:10 dilutions of all samples were prepared at various time points (after 1 h, 3 h, and 6 h). For the positive control, an additional dilution was prepared immediately after culture addition (0 min) and plated using a spiral plate. Throughout the entire test period, the samples were stored in an Eppendorf shaker at 1000 rpm and 30°C or 37°C. For the 1:10 dilutions, 900 µL of neutralization medium were placed in Eppendorf reaction vessels, and 100 µL of the culture-raw material suspension was added at the sampling time points. After completion of the test, all agar plates were placed in the incubator for incubation and evaluated on the Countermat after incubation.

[0044] The results are shown in Figures 4 and 5. It can be seen that the use of anisic acid, levulinic acid, or a combination of both substances inhibits the growth of the aerobic bacterium. S. epidermidis not significantly affected. In the case of the anaerobic bacterium C. acnes However, the use of anisic acid or levulinic acid alone does not lead to a reduction in cell count. Nevertheless, their combined use results in a significant selective antimicrobial effect.

Claims

1. Non-therapeutic use of a combination of (i) anisic acid or an antimicrobially active salt thereof and (ii) levulinic acid or an antimicrobially active salt thereof for selectively reducing the number of anaerobic bacteria of the species Cutibacterium acnes on the skin, wherein the number of aerobic bacteria of the species Staphylococcus epidermidis on the skin is not significantly reduced.

2. Non-therapeutic use according to claim 1, wherein the skin is facial skin.

3. Non-therapeutic use according to any of claims 1-2, wherein the two components of the combination are applied to the skin simultaneously or one after the other.

4. Non-therapeutic use according to any of claims 1-3, wherein the combination is administered in the form of a uniform composition comprising 0.01 to 5.0% (w / w), and preferably 0.1 to 1.0% (w / w), anisic acid or an antimicrobially active salt thereof.

5. Non-therapeutic use according to any one of claims 1-4, wherein the combination is administered in the form of a uniform composition comprising 0.01 to 5.0% (w / w), and preferably 0.1 to 1.0% (w / w / w), levulinic acid or an antimicrobially effective salt thereof.

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