Cosmetic stick compositions comprising an antiperspirant active

Abstract

A water-in-oil emulsion stick composition comprising an antiperspirant active, a structuring agent and lactic acid or salt thereof.

Description

[0001] COSMETIC STICK COMPOSITIONS COMPRISING AN ANTIPERSPIRANT ACTIVE

[0002] Field of Invention

[0003] The invention is concerned with water-in-oil emulsion stick compositions capable of boosting the level of selected natural skin benefit agents within the skin via topical application; the selected natural benefit agents being hyaluronic acid (HA) and ceramides.

[0004] There are numerous cosmetic treatments available for giving skin care benefits. Many of these focus on skin hydration and the prevention of dryness. In recent years, there has been a particular interest in augmenting the skin’s content of hyaluronic acid (HA), a natural component of the human body having very high water retention properties. Other publications have disclosed compositions delivering ceramides to the human skin.

[0005] HA may be formulated into a wide range of cosmetic skin care compositions and has been claimed to give numerous skin care benefits.

[0006] EP 2,347,755 B1 (Evonik, 2018) discloses cosmetic compositions comprising HA and other active ingredients for reducing skin wrinkles and / or the reduction of the depth of skin pores.

[0007] WO 2023 / 018959 (Roc Opco LLC, 2023) discloses anhydrous cosmetic compositions comprising HA for use in improving skin qualities, in particular hydration.

[0008] The present invention is concerned not with the delivery of HA or ceramides to the skin, but rather the boosting of the natural level of these skin benefit agents within the skin by the topically application of particular water-in-oil stick compositions comprising an antiperspirant active, a structuring agent and lactic acid or salt thereof. WO 2022 / 013101 (Unilever, 2022) discloses solid water-in-oil stick compositions comprising aluminium sesquichlorohydrate antiperspirant active; a solidifying agent; an emulsifier and at least 5% by weight of a polyol selected from glycerol, propylene glycol and / or PEG oligomers having a molecular weight of from 180 to 420.

[0009] Summary of Invention

[0010] It is an object of the invention to provide a water-in-oil emulsion stick composition comprising an antiperspirant active, a structuring agent and lactic acid or salt thereof. It is a particular object of the invention to provide such compositions that are solid sticks suitable for topical application to the skin of the human body. Such compositions are cosmetic compositions.

[0011] It is an object of the invention to provide a cosmetic composition that can boost the level of natural skin benefit agents within the skin by topical application, wherein the skin benefit agent is selected from hyaluronic acid and ceramides.

[0012] It is an object of some embodiments of the invention to provide a cosmetic composition that can boost the level of natural skin benefit agents within the skin by topical application and also deliver a deodorancy and / or antiperspirancy benefit, wherein the skin benefit agent is selected from hyaluronic acid and ceramides.

[0013] In a first aspect of the invention, there is provided a water-in-oil emulsion stick composition comprising an antiperspirant active, a structuring agent and lactic acid or salt thereof.

[0014] The structuring agent solidifies the water-in-oil emulsion, producing a solid stick composition.

[0015] Herein, “solid” and “solidified” refer to a state of matter incapable of flow at a temperature of 25°C and a pressure of 1 atmosphere. The water-in-oil emulsion stick composition is suitable for topical application and is a cosmetic stick composition. In preferred embodiments, the water-in-oil emulsion stick composition is suitable for all over body topical application, including both underarm areas and more intimate areas.

[0016] In a second aspect of the invention, there is provided a method of boosting the level of a skin benefit agent selected from hyaluronic acid or ceramides within the skin, said method comprising the topical application of a water-in-oil emulsion stick composition according to the first aspect of the invention. In preferred embodiments, this method may also produce deodorancy and / or antiperspirancy benefits.

[0017] In a third aspect of the invention, there is provided the use of a water-in-oil emulsion stick according to the first aspect of the invention for boosting natural skin benefit agents within the skin, wherein the skin benefit agent is selected from hyaluronic acid and ceramides.

[0018] In a fourth aspect of the invention, there is provided the use of a water-in-oil emulsion stick composition according to the second aspect of the invention for additionally delivering a deodorancy benefit to the surface of the human body.

[0019] In a fifth aspect of the invention, there is provided the use of a water-in-oil emulsion stick composition according to the third or fourth aspect of the invention for additionally delivering an antiperspirancy benefit to the surface of the human body.

[0020] Detailed Description

[0021] Herein, features expressed as “preferred” with regard to a particular aspect of the invention should be understood to be preferred with regard to each aspect of the invention (likewise, features expressed as “more preferred”, “particularly preferred” or “most preferred”). “Preferred” features typically aid the delivery of one or more of the objects of the invention. Herein, preferred features of the invention are particularly preferred when used in combination with other preferred features (likewise, features expressed as “more preferred”, “particularly preferred” or “most preferred”).

[0022] Herein, “ambient conditions” refer to 20°C and 1 atmosphere pressure, unless otherwise indicated.

[0023] Herein, “water insoluble” refers to materials having a solubility in water of less than 0.1 g / 100g, under ambient conditions.

[0024] Herein, all percentages, ratios and amounts are by weight, unless otherwise indicated.

[0025] Herein, amounts and concentrations of ingredients are percentages by weight of the total composition, unless otherwise indicated.

[0026] Herein, references to amounts of components such as “structuring agent” or “antiperspirant active” relate to the total amount of such components present in the composition.

[0027] Herein, the word “comprising” is intended to mean “including” but not necessarily “consisting of’, i.e. , it is non-exhaustive.

[0028] Herein, all uses, methods and compositions should be understood to be cosmetic uses, methods and compositions; that is to say, non-therapeutic uses, methods and compositions.

[0029] Herein, the oil-in-water emulsion sticks referred to in the first aspect of the invention and elsewhere are cosmetic compositions.

[0030] Herein, references to the dermis refer in particular to the papillary dermis, the top level of the dermis located immediately below the epidermis. Herein, “an antiperspirancy benefits” refers to reduction of perspiration on the surface of the human body, i.e. the skin.

[0031] The present invention uses water-in-oil emulsion sticks comprising lactic acid or a salt thereof. In this particular invention, the lactic acid is used to boost the natural level of selected skin benefit agents within the skin, in particular within the stratum corneum (SC), the epidermis and / or the dermis.

[0032] The selected skin benefit agents referred to in the paragraph immediately above are HA and ceramides. The HA boosting effect is seen principally in the epidermis and / or dermis whilst the ceramides boosting effect is seen principally in the SC.

[0033] Hyaluronic acid (HA) is a skin benefit agent which is a polymer of disaccharides, themselves composed of D-glucuronic acid and D-N-acetylglucosamine, linked via alternating p-1 ,4 and p-1 ,3 glycosidic bonds. HA is a major component of skin, where it is involved in several processes, including tissue hydration and repair and fibroblast proliferation. HA is a key component of the extracellular matrix helping to maintain the integrity of the epidermis and the dermis.

[0034] The stratum corneum (SC) is the uppermost layer of the skin, composed of from 5 to 30 cellular layers. The main unit of the SC is the corneocyte, a cell filled by a hydrophilic mass of keratin filaments and surrounded by a lipid-rich extracellular matrix. One of the most important intercellular lipids surrounding the corneocytes are ceramides, representing 50% of the total lipidic mass of the SC. Intercellular lipids, including ceramides, help to maintain skin hydration. In addition, they represent a physical barrier protecting the epidermis. Hence, ceramides are a skin benefit agent.

[0035] The total amount of lactic acid and salts thereof is preferably at least 0.1 , more preferably at least 0.5% and most preferably at least 1%. At the upper levels of incorporation, the AHA and salts thereof is preferably 20% or less, more preferably 12% or less and most preferably 6% or less. Preferred ranges may be formed from any of the lower and upper incorporation preferences indicated in this paragraph; e.g., from 0.5 to 20%. The structuring agent employed may be a single structural or a mixture of structurants. The amount of the structuring agent used is preferably from 5%, more preferably from 7% and most preferably from 8%. The upper amount is preferably up to 25%, more preferably up to 20% and most preferably up to 15%. The preferred ranges of solidifying agent may be selected from any of the lower and upper amounts indicated in this paragraph.

[0036] The structuring agent mentioned immediately above is preferably a wax. More preferably the structuring agent is a polyolefin wax, in particular a polyethylene wax. Such waxes are typically synthetic waxes, i.e. waxes synthesised from olefins in the case of polyolefin waxes and waxes synthesised from ethylene in the case of polyethylene waxes.

[0037] The aqueous phase of water-in-oil emulsions used in accordance with the invention typically comprises from 30 to 68% of the total composition. Preferably, it comprises from 40 to 65% and more preferably from 45 to 60% of the total composition.

[0038] An essential component of compositions of the invention is an antiperspirant active. Such active may be a conventional aluminium-containing active or it may be a non-aluminium active. Non-aluminium actives are preferred in compositions for all over body use.

[0039] In some preferred embodiments, an aluminium-containing antiperspirant active that is an astringent aluminium salt or aluminium-zirconium salt is employed. Such salts are typically dissolved in the aqueous disperse phase of the emulsion and are commonly present in emulsion sticks used in accordance with the invention.

[0040] A preferred aluminium-containing antiperspirant active is aluminium sesquichlorohydrate (ASCH). ASCH has the chemical formula of AI2OH4.4CI1.6 to AI2OH4.9CI1.1. Most commercial ASCH samples are of chemical formula AI2OH4.7CI1.3 to AI2OH4.9CI1.1 and it is particularly preferred to use actives of this formula.

[0041] Particularly preferred aluminium-containing AP actives comprise calcium and particularly preferred actives also comprise an amino acid, in particular glycine. Such actives are described in WO 2014 / 187685 (Unilever, 2014). The calcium is typically added in the form of calcium chloride. It is especially preferred that such actives are calcium-activated ASCH salts.

[0042] AP actives that are complexes with glycine are preferred, particularly when they also comprise calcium and / or are activated by calcium.

[0043] In certain especially preferred embodiments, a calcium-activated ASCH glycine complex is used.

[0044] The proportion of antiperspirant salt is calculated excluding the weight of any water of hydration but including any complexing agent that may be present, such as glycine and any activating agent, such as calcium chloride.

[0045] The weight concentration of the antiperspirant salt in the aqueous phase is commonly not higher than 50% and is advantageously at least 10%. In preferred embodiments its weight concentration is from 15 to 40% and in more preferred embodiments it is from 20 to 30%.

[0046] The weight of antiperspirant salt in the entire composition is usually at least 6% and is commonly up to 30%. The range of antiperspirant salt concentration for the composition is preferably from 8% to 25% and more preferably from 10 to 20%.

[0047] In preferred embodiments, the water-in-oil emulsion stick composition is used for boosting hyaluronic acid levels in the human skin and delivering an antiperspirancy benefit, i.e. , a reduction in perspiration on the surface of the human skin.

[0048] A preferred additional component in compositions used in the invention is a humectant selected from glycerol and / or a PEG oligomer of weight average molecular weight of from 180 to 420. Glycerol is an especially preferred humectant. The humectant may enhance the skin care properties of the composition. When employed, the humectant is present at a preferred level of from 1 to 25%, more preferably from 5 to 22% and most preferably from 10 to 20%, these levels being particularly relevant when the humectant is glycerol. A preferred additional component in compositions used in the invention is a water soluble vitamin, such as Vitamin B3 or niacinamide. Such vitamins are present at a level at a preferred level of from 0.1 to 8%, more preferably from 0.5 to 6% and most preferably from 1 to 5% by weight of the total composition. Such vitamins may enhance the skin care properties of the composition.

[0049] A preferred additional component in compositions used in the invention is a fragrance oil, alternatively known as a perfume oil. The fragrance oil may comprise a single fragrance component or, more commonly, a plurality of fragrance components. Herein, fragrance oils impart an odour, preferably a pleasant odour, to the composition. Preferably, the fragrance oil imparts a pleasant odour to the surface of the human body the composition is applied to the same.

[0050] The amount of fragrance oil in the composition is preferably up to 3%, advantageously is at least 0.5% and particularly preferably from 0.8% to 2%.

[0051] In certain embodiments, it is preferred to include an oil, other than a fragrance oil, that has a relatively low viscosity, by which is meant less 250 cS (mm2.s’1). Such oils, termed “non-fragrance oils”, can improve the sensory properties of the composition on application and can lead to other benefits such as emolliency.

[0052] Preferred non-fragrance oils are alkyl ether oils having a boiling point of above 100°C and especially above 150°C, including polyalkyleneglycol alkyl ethers. Such ethers desirably comprise between 10 and 20 ethylene glycol or propylene glycol units and the alkyl group commonly contains from 4 to 20 carbon atoms. The preferred ether oils include polypropylene glycol alkyl ethers such as PPG-14-butylether and PPG-15-stearyl ether.

[0053] Other preferred non-fragrance are triglyceride oils. The triglyceride oils commonly comprise the alkyl residues of aliphatic C?to Cis acids, the total number of carbon atoms being selected in conjunction with the extent of olefinic unsaturation and / or branching to enable the triglyceride to be liquid at 20°C. Particularly preferably, in the triglyceride oil the alkyl residues are linear Cis groups having one, two or three olefinic degrees of unsaturation, two or three being optionally conjugated, many of which are extractable from plants (or their synthetic analogues), including triglycerides of oleic acid, linoleic acid, conjugated linoleic acids, linolenic acid, petroselenic acid, ricinoleic acid, linolenelaidic acid, trans 7-octadecenoic acid, parinaric acid, pinolenic acid, punicic acid, petroselenic acid and stearidonic acid.

[0054] Suitable oils can include those derived from unsaturated Cis acids, including coriander seed oil, impatiens balsimina seed oil, parinarium laurinarium kernel fat oil, sabastiana brasilinensis seed oil, dehydrated castor seed oil, borage seed oil, evening primrose oil, aquilegia vulgaris oil, sunflower (seed) oil and safflower oil. Other suitable oils are obtainable from hemp, and maize corn oil. An especially preferred oil by virtue of its characteristics is sunflower (seed) oil.

[0055] Further suitable oils, that can also be emollient oils, comprise alkyl or alkyl-aryl ester oils having a boiling point of above 150°C (and a melting point of below 20°C). Such ester oils include oils containing one or two alkyl groups of 12 to 24 carbon atoms length, including isopropyl myristate, isopropyl palmitate and myristyl palmitate. Other nonvolatile ester oils include alkyl or aryl benzoates such C12-15 alkyl benzoate, for example Finsolv TN™ or Finsolv Sun™.

[0056] Other components that may be included in composition used in the invention include those described in the following paragraphs.

[0057] Wash-off agents may be included, often in an amount of up to 10%, to assist in the removal of the formulation from skin or clothing. Such wash-off agents are typically nonionic surfactants such as esters or ethers containing a Cs to C22 alkyl moiety and a hydrophilic moiety comprising a polyoxyalkylene group (POE or POP).

[0058] Skin-feel improvers (e.g. talc or finely divided high molecular weight polyethylene), may be included, typically in an amount from 1 up to 10%.

[0059] An optional component is a preservative system, such as sodium benzoate / citric acid and / or an antioxidant such BHT (butyl hydroxy toluene), each typically in an amount of from 0.01 to 0.5%.

[0060] The following Examples are illustrative of the invention and non-limiting as to its scope.

[0061] The deodorant stick compositions indicated in Table 1 were prepared by methods known in the art. They differed only in the presence of potassium lactate in one and its replacement by water in the other. The Examples had good solidity and stability.

[0062] The Examples / products were tested in the following 3-day study. The results are indicated at the base of Table 1.

[0063] Human skin explants of average diameter 12 mm were prepared from tissue removed in an abdominoplasty procedure. The explants were kept in survival in BEM culture medium (BIO-EC’s bespoke Explant medium) at 37°C in a humid, 5% CO2 atmosphere.

[0064] On day 1 of the study, explants were treated topically with a paper disk soaked with a 1.25% w / w aqueous solution of sodium dodecyl sulphate (SDS), to induce irritation stress in the explants. Doing this increases the sensitivity of the explants to subsequent treatments. It also enables the subsequently applied treatments to be tested as to their ability to help skin recover from stress events. The paper disks were removed after 24 hours of contact and the products to be tested were applied immediately afterwards. Products were applied topically at 2 mg per 1 cm2explant and spread using a spatula. The culture medium was half renewed (1 ml) on day 1 and fully renewed (2 ml) on day 2. Control explants did not receive any treatment except the culture medium renewal.

[0065] On day 3 of the study, FFPE (formal-fixed paraffin-embedded) skin sections of the explants were prepared. These were sliced into 5 micron sections using a microtone. Hyaluronic acid immunostaining of the FFPE sections was performed with a biotinylated hyaluronic acid binding protein (HABP, Amsbio ref. AMS.HKD.BC41) diluted at 1:400 in PBS, BSA 0.3% for 1 hour at room temperature, with a biotin / streptavidin amplifying system and revealed by VIP (Vector laboratories, Ref. SK-4600), a substrate of peroxidase giving a violet stain once oxidised. The immunostaining was assessed by microscopical observation and semi-quantified by image analysis using the software cellSens (Olympus).

[0066] Ceramide immunostaining of the FFPE sections was performed with an anti-ceramides monoclonal antibody (Glycobiotech, ref. MAB_0013, clone S58-9) diluted at 1:400 in PBS, BSA 0.3% overnight at room temperature, with a biotin / streptavidin amplifying system and revealed by VIP (Vector laboratories, Ref. SK-4600), a substrate of peroxidase giving a violet stain once oxidised. The immunostaining was assessed by microscopical observation and semi-quantified by image analysis using the software cellSens (Olympus).

[0067] Samples from the epidermal layer and papillary dermis layer of the skin were analysed for HA and a comparison made between those treated with the Examples indicated in Table 1 and control samples treated as described above. The average results and standard deviations (n = 9) are given at the base of Table 1. The HA levels quoted refer to the percentage of the sample surface on which HA was found to be present.

[0068] Samples from the stratum corneum of the skin were analysed for ceramides and a comparison made between those treated with the Examples indicated in Table 1 and control samples treated as described above. The average results and standard deviations (n = 9) are given at the base of Table 1. The ceramide levels quoted refer to the percentage of the sample surface on which ceramide was found to be present.

[0069] Treatment with the 1.25% SLS solution reduced the hyaluronic acid level of the epidermis by 56% by day 3 of the study: from 22.2% coverage to 9.8% coverage. When the epidermis was post-treated with P1 , the HA level was increased by 32% compared with the SLS treatment alone. When the epidermis was post-treated with P2, the HA level was increased by 58% compared with the SLS treatment alone, this difference being significant at the 99% level. Table 1 Treatment with the 1.25% SLS solution reduced the hyaluronic acid level of the dermis by 59% by day 3 of the study: from 45.8% coverage to 18.6% coverage. When the explants were post-treated with P1 , the HA level was increased by 90% compared with the SLS treatment alone. When the explants were post-treated with P2, the HA level was increased by 167% compared with the SLS treatment alone. This difference in performance between P1 and P2 was significant at the 95% level. Treatment with the 1.25% SLS solution reduced the ceramide level of the stratum corneum by 78% by day 3 of the study: from 80.0% coverage to 17.3% coverage. When the stratum corneum was post-treated with P3, the ceramide level was increased by 32% compared with the SLS treatment alone, which was not significant. When the stratum corneum was post-treated with P1 , the ceramide level was increased by 305% compared with the SLS treatment alone, which was significant at the 99% level. The difference between the ceramide levels resulting from P3 treatment and the P1 treatment was significant at the 99% level.

[0070] To further illustrate the effect of stressing the skin with SDS and then post-treating with Example P1, please see Figures 1 to 3. Each of the figures are magnified cross-sectional images of skin sections with the ceramide stained violet as described above.

[0071] Figure 1 is an image of an unstressed, healthy control sample with a high content of ceramide in the stratum corneum. This is indicated by the strongly coloured “ribbon” towards the skin surface (top of the image).

[0072] Figure 2 is an image of a skin cross-section 2 days after treatment with 1.25% aqueous SLS solution. It is clear that the ceramide content is greatly reduced, evidenced by the much reduced colour in the stratum corneum.

[0073] Figure 3 is an image of a skin cross-section that has been stressed with SLS and then post-treated with Example P1 as described above. It is clear that the ceramide content has been largely restored by the potassium lactate contained in Example P1.

[0074] Clearly, water-in-oil stick compositions according to the invention offer significant skin care benefits.

Claims

Claims1. A water-in-oil emulsion stick composition comprising an antiperspirant active, a structuring agent and lactic acid or salt thereof.

2. A stick composition according to claim 1 , wherein the structuring agent is a wax.

3. A stick composition according to claim 2, wherein the wax is a polyethylene.

4. A stick composition according to any one of the preceding claims which is solid, i.e. incapable of flow at a temperature of 25°C and a pressure of 1 atmosphere.

5. A stick composition according to any one of the preceding claims, comprising a humectant selected from glycerol and / or a PEG oligomer of weight average molecular weight of from 180 to 420.

6. A stick composition according to claim 5, comprising glycerol at from 5 to 22% by weight.

7. A stick composition according to any one of the preceding claims which is suitable for all over body use.

8. A stick composition according to any one of the preceding claims wherein the antiperspirant active comprises aluminium sesquichlorohydrate.

9. A stick composition according to claim 8 wherein the antiperspirant active comprises an amino acid and calcium chloride.

10. A stick composition according to any one of the preceding claims, comprising a non-aluminium antiperspirant active.

11. A method of boosting the level of a skin benefit agent selected from hyaluronic acid or ceramides within the skin, said method comprising the topical application of a water-in-oil emulsion stick composition according to any one of the preceding claims.

12. The non-therapeutic use of a water-in-oil emulsion stick composition according to any of claims 1 to 10 for boosting natural skin benefit agents within the skin, wherein the skin benefit agent is selected from hyaluronic acid and ceramides.

13. The non-therapeutic use of a water-in-oil emulsion stick composition according to claim 12, wherein a deodorancy benefit is also delivered to the skin of the human body.

14. The non-therapeutic use of a water-in-oil emulsion stick composition according to claim 12 or claim 13, wherein an antiperspirancy benefit is also delivered to the skin of the human body.

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