Peeling agent and peeling method using same

Abstract

The present invention makes it possible to provide a peeling agent which is for separating an epidermis of a skin from a surface layer and which comprises a methyllactic acid and water, wherein, of the total content of the methyllactic acid and water, the methyllactic acid content is 0.1-70 mass% and the water content is 99.9-30 mass%, and the pH of the peeling agent is 0.5-12.

Description

Peeling agent and peeling method using same

[0001] The present invention relates to a peeling agent that can remove wrinkles, age spots (pigmentation such as senile lentigo), and dullness from the skin, as well as treat acne and improve oily skin. The present invention also relates to a peeling method using the peeling agent. In this specification, the peeling agent refers to a peeling agent used as a pharmaceutical or cosmetic.

[0002] In recent years, α-hydroxy acids such as glycolic acid, lactic acid, malic acid, and tartaric acid have been incorporated into topical skin preparations, such as cosmetics, as preparations for improving skin texture, dullness, roughness, etc., due to their ability to exfoliate the old stratum corneum on the skin surface, regenerate a new stratum corneum, and promote epidermal turnover (metabolism). These compounds are also used in chemical peels to remove fine wrinkles, age spots, freckles, melasma, various pigmentations such as age spots, acne, dermatitis scars, burns, thermal burns, wounds, and scars, as well as wrinkles and age spots on the skin (e.g., Patent Documents 1 and 2). The improvement of skin texture, dullness, acne, etc., achieved by these agents increases with their incorporation; however, excessive incorporation can result in a low pH, skin irritation, and desquamation due to excessive promotion of skin turnover. As a result, the application of topical preparations containing a high amount of α-hydroxy acid or the like has led to problems such as dryness, rough skin, or inflammation.

[0003] For example, attempts have been made to combine medicinal ingredients having anti- or moisturizing effects, such as amino acids, polysaccharides, lipids, animal and plant extracts, tranexamic acid, and L-ascorbic acid, with conventional α-hydroxy acids, etc. (See, for example, Patent Documents 1 to 6.) However, considering the side effects and diminished peeling effect that may result from the incorporation of other medicinal ingredients, it is desirable to use a substance whose α-hydroxy acid structure itself has physical properties that are more suitable for peeling, but to date, no satisfactory substance has been found.

[0004] JP 8-259443 JP 8-283138 JP 10-114642 JP 2000-186036 JP 2005-281135 JP 2008-50358

[0005] The present invention aims to solve at least one of the above-mentioned problems in the prior art, and further aims to provide a peeling agent that has a good balance between peeling performance and low irritation.

[0006] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the following invention. Specifically, the present invention is as follows. <1> A peeling agent for peeling the epidermis from the surface layer of skin, containing methyl lactic acid and water, wherein the content of the methyl lactic acid is 0.1 to 70% by mass and the content of the water is 99.9 to 30% by mass relative to the total amount of the methyl lactic acid and water, and the pH of the peeling agent is 0.5 to 12. <2> The peeling agent according to <1> above, further containing a thickener. <3> The peeling agent according to <2> above, wherein the content of the thickener is 0.01 to 5% by mass relative to the total amount of the peeling agent. <4> The peeling agent according to any one of <1> to <3> above, wherein the acne bacteria removal rate is 99.0% or more after the peeling agent is added to an acne bacteria test solution and allowed to stand at room temperature for 30 seconds. <5> The peeling agent according to any one of <1> to <4> above, which does not contain any hydroxycarboxylic acid other than methyllactic acid. <6> A peeling method for peeling the epidermis from the surface layer of skin, comprising the step of applying the peeling agent according to any one of <1> to <5> above to skin and peeling the epidermis from the surface layer of the skin. <7> The peeling method according to <6> above, which is a cosmetic peeling method for reducing the visibility of at least one of wrinkles, fine lines, pigmentation marks, and scars. <8> The peeling method according to <6> or <7> above, wherein the reduction rate of the stratum corneum in the skin after the peeling step, when calculated by the following formula (1), is 35 to 50%. (1) Stratum corneum reduction rate = (stratum corneum thickness when water is used - stratum corneum thickness when the peeling agent is used) / (stratum corneum thickness when water is used) × 100 (%)

[0007] According to the present invention, a peeling agent having a good balance between peeling performance and low irritation can be provided. Furthermore, according to a preferred embodiment of the present invention, the peeling agent has bactericidal properties and can restore the skin to a normal state.

[0008] FIG. 1 is an explanatory diagram showing the experimental procedure in Example 1. FIG. 2 is a phase contrast microscope photograph of a cross section of the skin in Example 1. FIG. 3 is a phase contrast microscope photograph of a cross section of the skin in Comparative Example 1. FIG. 4 is a phase contrast microscope photograph of a cross section of the skin in Comparative Example 2. FIG. 5 is a phase contrast microscope photograph of a cross section of the skin in Comparative Example 3. FIG. 6 is a phase contrast microscope photograph of a cross section of the skin in Comparative Example 4. FIG. 7 is an external photograph of an agar medium in Example 2. FIG. 8 is an external photograph of an agar medium in Comparative Example 5.

[0009] The present invention will be described in detail below. A first embodiment of the present invention is a peeling agent for peeling the epidermis from the surface layer of skin, containing methyl lactic acid and water, wherein the methyl lactic acid content is 0.1 to 70% by mass, the water content is 99.9 to 30% by mass, and the pH of the peeling agent is 0.5 to 12, relative to the total amount of the methyl lactic acid and water. The peeling agent of the present invention is a topical skin preparation. As used herein, the term "peeling agent" refers to an agent used in chemical peeling, in which a chemical substance is applied to the skin and the surface layer is peeled to a certain depth by its action. As used herein, the epidermis of the skin refers to the stratum corneum, stratum granulosum, stratum spinosum, and stratum basale. By incorporating methyl lactic acid, the present invention can provide a peeling agent with a balance of low irritation and peeling properties. Furthermore, according to a preferred embodiment of the present invention, the peeling agent can be used as a topical skin preparation with minimal dryness, inflammation, or rough skin. Furthermore, according to a preferred embodiment of the present invention, the peeling agent has an unexpected effect of bactericidal properties that improve skin cleanliness.

[0010] A second embodiment of the present invention is a peeling method for peeling the epidermis from the surface layer of skin, comprising the step of applying the peeling agent of the first embodiment to skin and peeling the epidermis from the surface layer of the skin. A preferred embodiment of the present invention is a cosmetic peeling method for reducing the visibility of at least one of wrinkles, fine lines, pigmentation marks, and scars. That is, a preferred embodiment of the present invention is a cosmetic peeling method that does not include a method for treating human diseases. In the peeling method of the present invention, the reduction rate of the stratum corneum on the skin after the peeling step, as calculated by the following formula (1), is preferably 35 to 50%, more preferably 40 to 45%. (1) Stratum corneum reduction rate = (stratum corneum thickness when water is used - stratum corneum thickness when the peeling agent is used) / (stratum corneum thickness when water is used) × 100 (%). A reduction rate of the stratum corneum on the skin after the peeling step within the above range is preferred from the viewpoint of a balance between low irritation and peeling properties.

[0011] The peeling agent of the present invention contains methyl lactic acid as an essential ingredient. To date, no peeling agent containing methyl lactic acid as an essential ingredient has been known, nor has its bactericidal properties been known. In view of side effects, it is preferable that the peeling agent of the present invention does not contain any other medicinal ingredients. Furthermore, it is preferable that the peeling agent of the present invention does not contain any hydroxycarboxylic acids other than methyl lactic acid. The structure of methyl lactic acid is represented by the following structural formula, and it is also called 2-hydroxybutyric acid or 2-methyl lactic acid.

[0012] The peeling agent of the present invention contains 0.1 to 70% by mass of methyl lactic acid and 99.9 to 30% by mass of water relative to the total amount of methyl lactic acid and water. However, when used at high concentrations under the guidance of a doctor, the methyl lactic acid content is preferably 10 to 70% by mass, the water content is preferably 90 to 30% by mass, the methyl lactic acid content is more preferably 20 to 60% by mass, the water content is more preferably 80 to 40% by mass, the methyl lactic acid content is particularly preferably 30 to 50% by mass, and the water content is particularly preferably 70 to 50% by mass. A methyl lactic acid content of less than 10% by mass may not be sufficient to improve wrinkles, age spots, etc., while a content of more than 70% by mass may cause significant skin irritation and make viscosity adjustment difficult. When methyl lactic acid is contained in a high amount, such as 10 to 70% by mass, it is effective in improving skin texture, dullness, acne, etc.

[0013] On the other hand, when the peeling agent of the present invention is used as a general cosmetic or quasi-drug, that is, when used in a low concentration formulation, the content of methyl lactic acid relative to the total amount of methyl lactic acid and water is preferably 0.1 to 7% by mass. At concentrations lower than this, the effect is lost. On the other hand, when the concentration is higher, the effect is greater, but irritation to the skin increases, making it difficult to use except in a medical environment.

[0014] The peeling agent of the present invention preferably has an acne bacteria removal rate of 99.0% or more, more preferably 99.1% or more, and particularly preferably 99.2% or more, after the peeling agent is added to an acne bacteria test solution and allowed to stand at room temperature for 30 seconds. In the present invention, the acne bacteria removal rate can be measured by the method described in Example 3 below.

[0015] The pH of the peeling agent of the present invention is 0.5 to 12, preferably 0.5 to 7, more preferably 1 to 5, and particularly preferably 1.5 to 3.

[0016] The peeling agent of the present invention preferably further contains a thickener. In this case, the content of the thickener is preferably 0.01 to 5% by mass, more preferably 0.1 to 2% by mass, based on the total amount of the peeling agent. Examples of thickeners that may be further added include, but are not limited to, gellan gum, native gellum gum arabic, carrageenan, karaya gum, tragacanth gum, carob gum, quince seed (marmelo), casein, dextrin, gelatin, sodium pectinate, sodium allaginate, methylcellulose, ethylcellulose, CMC (carboxymethylcellulose), hydroxyethylcellulose, hydroxypropylcellulose, PVA (polyvinyl alcohol), PVM (polyvinyl methyl ether), PVP (polyvinylpyrrolidone), sodium polyacrylate, carboxyvinyl polymer, locust bean gum, guar gum, tamarind gum, dialkyldimethylammonium cellulose sulfate, xanthan gum, agar, bentonite, hectorite, AlMg silicate (veegum), and laponite. These thickeners may be blended into the peeling agent of the present invention either alone or in combination of two or more kinds, as required. The order of mixing these is not particularly specified.

[0017] The viscosity of the peeling agent of the present invention is not particularly limited, but the viscosity at room temperature (25°C) is preferably 500 to 5000 mPa·s, and more preferably 1000 to 3000 mPa·s. When the viscosity is within this range, the peeling agent is less likely to drip during use and has excellent usability. In the present invention, an EMS viscometer (EMS-1000, manufactured by Kyoto Electronics Sangyo Co., Ltd.) was used to measure the viscosity.

[0018] Alternatively, the viscosity can be increased by using a pigment such as talc to give the peeling agent a clay-like consistency. In this case, the peeling agent of the present invention can be mixed with a pigment such as talc to a desired viscosity that does not drip, to form a paste, which can then be thickened.

[0019] The peeling agent of the present invention may further contain a moisturizing agent. Examples of the moisturizing agent to be contained include, but are not limited to, glycerin, diglycerin, 1,3-butylene glycol, propylene glycol, dipropylene glycol, sorbitol, fructose, mannose, erythritol, trehalose, xylitol, chondroitin sulfate, hyaluronic acid, mucoitin sulfate, and caronic acid. 1,3-Butylene glycol is particularly preferred. These moisturizing agents may be contained in the peeling agent of the present invention alone, or two or more types may be contained in combination as needed.

[0020] The amount of the moisturizing agent in the peeling agent of the present invention is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass, based on the total amount of the peeling agent.

[0021] The peeling agent of the present invention is not particularly limited as long as it is applied to the outer skin, and includes cosmetics, pharmaceuticals, quasi-drugs, etc. The formulation may also be any formulation, such as an aqueous solution, solubilized, emulsion, oil, gel, paste, ointment, aerosol, water-oil two-layer system, or water-oil-powder three-layer system. It also includes those supported on a sheet-like base.

[0022] The form of use may also be arbitrary, and it may be used in any form such as a lotion, emulsion, cream, pack, beauty serum, face wash, soap, etc.

[0023] The peeling agent of the present invention can be prepared by a conventional method according to the desired dosage form by appropriately blending, as needed, other optional ingredients that are normally used in external skin preparations such as cosmetics and pharmaceuticals in addition to the above-mentioned ingredients. For example, the peeling agent of the present invention can be prepared by blending the above-mentioned ingredients with one or more of the following ingredients:

[0024] Examples of the ultraviolet absorber include benzoic acid-based ultraviolet absorbers such as para-aminobenzoic acid (hereinafter abbreviated as "PABA"), PABA monoglycerin ester, N,N-dipropoxy PABA ethyl ester, N,N-diethoxy PABA ethyl ester, N,N-dimethyl PABA ethyl ester, N,N-dimethyl PABA butyl ester, and N,N-dimethyl PABA methyl ester; anthranilic acid-based ultraviolet absorbers such as homomenthyl-N-acetylanthranilate; amyl salicylate, menthyl salicylate, and homomenthyl salicylate; methyl lactic acid-based ultraviolet absorbers such as phenyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, and p-isopropanol phenyl salicylate; octyl cinnamate, ethyl-4-isopropyl cinnamate, methyl-2,5-diisopropyl cinnamate, ethyl-2,4-diisopropyl cinnamate, methyl-2,4-diisopropyl cinnamate, propyl-p-methoxycinnamate, isopropyl-p-methoxycinnamate, isoamyl-p-methoxycinnamate, octyl-p- Cinnamic acid-based ultraviolet absorbers such as methoxycinnamate (2-ethylhexyl-p-methoxycinnamate), 2-ethoxyethyl-p-methoxycinnamate, cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenylcinnamate, 2-ethylhexyl-α-cyano-β-phenylcinnamate, glyceryl mono-2-ethylhexanoyl-di-paramethoxycinnamate, and methyl bis(trimethylsiloxane)silylisopentyl trimethoxycinnamate; 3-(4'-methylbenzylidene)-d,l-cinnamate; Examples of such compounds include camphor, 3-benzylidene-d,l-camphor, urocanic acid, urocanic acid ethyl ester, 2-phenyl-5-methylbenzoxazole, 2,2'-hydroxy-5-methylphenylbenzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenylbenzotriazole, dibenzalazine, dianisoylmethane, 4-methoxy-4'-t-butyldibenzoylmethane, and the like, and any one or more of these may be used.

[0025] Examples of ultraviolet scattering agents include powders of titanium oxide, fine particle titanium oxide, zinc oxide, fine particle zinc oxide, iron oxide, fine particle iron oxide, and cerium oxide.

[0026] These ultraviolet scattering agents are usually used in the form of needle-, spindle-, spherical, or granular powders, and are preferably fine-particle powders with a particle size of 0.1 μm or less.

[0027] Examples of liquid oils and fats include avocado oil, camellia oil, turtle oil, macadamia nut oil, corn oil, mink oil, olive oil, rapeseed oil, egg yolk oil, sesame oil, persic oil, wheat germ oil, camellia oil, castor oil, linseed oil, safflower oil, cottonseed oil, perilla oil, soybean oil, peanut oil, tea seed oil, kaya oil, rice bran oil, Chinese tung oil, Japanese tung oil, jojoba oil, germ oil, and triglycerin.

[0028] Examples of solid fats and oils include cacao butter, coconut oil, horse fat, hardened coconut oil, palm oil, beef tallow, mutton tallow, hardened beef tallow, palm kernel oil, lard, beef bone fat, Japan wax kernel oil, hardened oil, beef trotter fat, Japan wax, and hardened castor oil.

[0029] Examples of waxes include beeswax, candelilla wax, cotton wax, carnauba wax, bayberry wax, ivory wax, whale wax, montan wax, rice bran wax, lanolin, kapok wax, lanolin acetate, liquid lanolin, sugarcane wax, lanolin fatty acid isopropyl, hexyl laurate, reduced lanolin, jojoba wax, hard lanolin, shellac wax, POE lanolin alcohol ether, POE lanolin alcohol acetate, POE cholesterol ether, lanolin fatty acid polyethylene glycol, and POE hydrogenated lanolin alcohol ether.

[0030] Examples of hydrocarbon oils include liquid paraffin, ozokerite, squalane, pristane, paraffin, ceresin, squalene, petrolatum, microcrystalline wax, polyethylene wax, and Fischer-Tropsch wax.

[0031] Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, undecylenic acid, tall acid, linoleic acid, linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

[0032] Examples of higher alcohols include straight-chain alcohols (e.g., lauryl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, myristyl alcohol, oleyl alcohol, cetostearyl alcohol, etc.); branched-chain alcohols (e.g., monostearyl glycerin ether (batyl alcohol), 2-decyltetradecynol, lanolin alcohol, cholesterol, phytosterol, hexyldodecanol, octyldodecanol, etc.); and the like.

[0033] Examples of synthetic ester oils include isopropyl myristate, cetyl octanoate, octyldodecyl myristate, isopropyl palmitate, butyl stearate, hexyl laurate, myristyl myristate, decyl oleate, hexyldecyl dimethyloctanoate, cetyl lactate, myristyl lactate, lanolin acetate, isocetyl stearate, isocetyl isostearate, cholesteryl 12-hydroxystearate, ethylene glycol di-2-ethylhexanoate, dipentaerythritol fatty acid esters, N-alkyl glycol monoisostearate, neopentyl glycol dicaprate, diisostearyl malate, glycerin di-2-heptylundecanoate, trimethylolpropane tri-2-ethylhexanoate, trimethylolpropane triisostearate, pentaerythritol tetra-2-ethylhexanoate, tri-2-ethylhexanoate, Glyceryl xanthate, glyceryl trioctanoate, glyceryl triisopalmitate, trimethylolpropane triisostearate, cetyl 2-ethylhexanoate, 2-ethylhexyl palmitate, glyceryl trimyristate, tri-2-heptylundecanoic acid glyceride, castor oil fatty acid methyl ester, oleyl oleate, acetoglyceride, 2-heptylundecyl palmitate, diisobutyric acid adipate 2-hexyldecyl palmitate, 2-hexyldecyl adipate, 2-ethylhexyl succinate, triethyl citrate, and polyoxyethylene-polyoxypropylene random polymer methyl ether.

[0034] Examples of silicone oils include chain polysiloxanes (e.g., dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, etc.); cyclic polysiloxanes (e.g., octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, etc.), silicone resins that form a three-dimensional network structure, silicone rubber, and various modified polysiloxanes (e.g., amino-modified polysiloxanes, polyether-modified polysiloxanes, alkyl-modified polysiloxanes, fluorine-modified polysiloxanes, etc.).

[0035] Examples of the base include potassium hydroxide, caustic soda, sodium citrate, sodium carbonate, sodium hydrogen carbonate (sodium bicarbonate), ammonia, triethanolamine, L-arginine, and L-lysine.

[0036] Other examples include lower alcohols such as ethanol; antioxidants such as butylhydroxytoluene, tocopherol, and phytin; antibacterial agents such as benzoic acid, sorbic acid, alkyl parahydroxybenzoates, and hexachlorophene; organic acids such as acyl sarcosinate (e.g., sodium lauroyl sarcosinate) and glutathione; vitamin A and its derivatives, vitamin B6 hydrochloride, vitamin B6 tripalmitate, vitamin B6 dioctanoate, vitamin B2 and its derivatives, vitamin B12, vitamin B15 and its derivatives, and ascorbic acid. , ascorbic acid sulfate (salt), ascorbic acid phosphate (salt), ascorbic acid dipalmitate and other vitamin Cs, α-tocopherol, β-tocopherol, δ-tocopherol, vitamin E acetate and other vitamins, vitamin Ds, vitamin H, pantothenic acid, pantethine and other vitamins; nicotinamide, benzyl nicotinate, γ-oryzanol, allantoin, glycyrrhizic acid (salt), glycyrrhetinic acid and its derivatives, hinokitiol, bisabolol, eucalptone, thymol, inositol, saikosaponin Saponins such as carrot saponin, loofah saponin, and soapberry saponin, pantothenyl ethyl ether, ethinylestradiol, tranexamic acid, arbutin, cepharanthine, and placenta extract, as well as various other drugs such as dock, sophora flavescens, water hyacinth, orange, sage, yarrow, mallow, Swertia japonica, thyme, Angelica acutiloba, spruce, birch, horsetail, loofah, horse chestnut, saxifrage, arnica, lily, mugwort, peony, aloe, gardenia, Spanish mackerel, hawthorn extract, St. John's wort extract, iris extract, and ascaea officinalis. Plant extracts such as kissa, ginkgo leaf extract, thyme extract, fennel extract, oolong tea extract, water lily extract, angelica tree extract, emmeiso extract, scutellaria root extract, phellodendron bark extract, white nettle extract, licorice extract, gardenia extract, black tea extract, sedge extract, tormentilla extract, rose extract, loofah extract, peppermint extract, rosemary extract, and royal jelly extract, pigments, sorbitan monolaurate, sorbitan monopalmitate, sorbitan sesquioleate, sorbitan trioleate,Examples of surfactants include nonionic surfactants such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyethylene glycol monooleate, polyoxyethylene alkyl ethers, polyglycol diethers, lauroyl diethanolamide, fatty acid isopropanolamide, maltitol hydroxy fatty acid ethers, alkylated polysaccharides, alkyl glucosides, and sugar esters; cationic surfactants such as stearyl trimethylammonium chloride, benzalkonium chloride, and laurylamine oxide; anionic surfactants such as sodium palmitate, sodium laurate, sodium laurate, potassium lauryl sulfate, alkyl triethanolamine sulfate ethers, turmeric oil, linear dodecyl benzene sulfate, polyoxyethylene hydrogenated castor oil maleic acid, and acyl methyl taurine; amphoteric surfactants; antioxidants such as δ-tocopherol and butylhydroxytoluene; and preservatives such as phenoxyethanol and parabens.

[0037] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. Methyl lactic acid used below was manufactured by Mitsubishi Gas Chemical Company. Furthermore, other reagents were manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. unless otherwise specified. Pig skin was purchased from Dart Corporation.

[0038] Examples of formulations of the peeling agent of the present invention are shown below as working examples, where the blending amounts are all expressed as % by mass relative to the total amount of the peeling agent.

[0039] Example 1 Methyl lactic acid was mixed with purified water to prepare a 50% aqueous solution (peeling agent). The resulting 50% aqueous solution of methyl lactic acid had a pH of 1.6 and a viscosity of 5.8 mPa·s at 25°C. After wiping pig skin with isopropanol, a cylindrical glass ring was attached to the skin. The 50% aqueous solution of methyl lactic acid was placed in the glass ring, and the skin was exposed to the 50% aqueous solution of methyl lactic acid at 37°C for 3 hours. After application, a paraffin block was prepared, and a cross section was cut out to prepare a section. The section was stained with hematoxylin and eosin (HE), and the cross section of the skin was observed under a phase-contrast microscope. The experimental procedure is shown in Figure 1. The observation results are shown in Figure 2. In Example 1, it was confirmed that the stratum corneum was peeled from the surface layer (having a peeling effect).

[0040] Comparative Example 1 Fig. 3 shows the results of treatment in which the skin was immersed in water for 3 hours instead of the 50% aqueous solution of methyl lactic acid used in Example 1. In Comparative Example 1, the stratum corneum was not peeled.

[0041] Comparative Example 2 Instead of the 50% aqueous solution of methyl lactic acid used in Example 1, the skin was immersed in a 50% aqueous solution of glycolic acid (pH 0.7) for 3 hours. The results are shown in FIG.

[0042] Comparative Example 3 Instead of the 50% aqueous solution of methyl lactic acid used in Example 1, the skin was immersed in a 50% aqueous solution of lactic acid (pH 1.0) for 3 hours. The results are shown in FIG.

[0043] Comparative Example 4 Instead of the 50% aqueous solution of methyl lactic acid used in Example 1, the skin was immersed in a 23% aqueous solution of glycolic acid (pH 1.6) for 3 hours. The results are shown in FIG.

[0044] In Comparative Examples 2 and 3, the stratum corneum was peeled from the deep layers, not from the surface. In Comparative Example 4, the stratum corneum was peeled very shallowly, and the peeling effect was significantly small. Glycolic acid had a low peeling effect at high pH, ​​but methyl lactic acid had sufficient peeling performance at high pH.

[0045] The stratum corneum thickness and stratum corneum reduction rate after peeling are summarized in Table 1 below. The stratum corneum thickness after peeling was measured at 5 locations on each of 5 images, for a total of 25 points, and the median was calculated. The stratum corneum reduction rate was calculated using the following formula: stratum corneum reduction rate = (stratum corneum thickness after water treatment - stratum corneum thickness after peeling agent treatment) / (stratum corneum thickness after water treatment) x 100 (%). stratum corneum reduction rate: Evaluation A: 35%≦stratum corneum reduction rate<50% Evaluation B: 50%≦stratum corneum reduction rate<70% Evaluation C: 70%≦stratum corneum reduction rate≦100% Evaluation D: stratum corneum reduction rate<35% By using methyl lactic acid, a peeling agent with high concentration and high pH can be obtained, which has low skin irritation and good control of peel depth, and it was confirmed that peel depth is sufficient even at high pH.

[0046] (Example 2) For the E. coli sterilization test, E. coli K12 strain (HB101) was used. E. coli and 5 mL of LB medium were used and cultured at 30°C for 20 hours. Then, 0.5 mL of dimethyl sulfoxide was added and mixed, and the mixture was stored in a freezer at -80°C. The turbidity (660 nm) of this solution was 5.8. The E. coli stock was 10 ６ The solution was diluted 1:1 with sterile water. 42 μL of this diluted solution was mixed with 100 μL of a 10% methyl lactic acid solution to prepare a 7% methyl lactic acid solution. After leaving it at 37°C for 15 minutes and then cooling on ice, the 7% methyl lactic acid solution was spread onto a 9 cm petri dish of nutrient agar medium (Eiken Pearl Core). It was cultured overnight at 37°C, and the number of colonies after culture was counted. This was repeated three times. Figure 7 shows the appearance of the agar medium after 15 minutes of application of the 7% methyl lactic acid solution and overnight culture. It can be seen from Figure 7 that all E. coli bacteria were killed by the methyl lactic acid treatment.

[0047] Comparative Example 5 The same procedure as in Example 2 was carried out. ６The solution was diluted 1:1 with sterile water. 42 μL of this diluted solution was mixed with 100 μL of sterile water to prepare the desired aqueous solution. After leaving it at 37°C for 15 minutes, it was cooled on ice and then the entire solution was spread onto a 9 cm petri dish of nutrient agar medium (Eiken Pearl Core). It was cultured overnight at 37°C, and the number of colonies after culture was counted. This was repeated three times. Figure 8 shows the appearance of the agar medium after 15 minutes of application of the aqueous solution obtained above and overnight culture. From Figure 8, it was observed that a large number of E. coli bacteria survived when treated with the aqueous solution obtained above.

[0048] The results of counting the number of E. coli colonies are shown in Table 2. As shown in Table 2, all E. coli were killed after treatment with methyl lactic acid. On the other hand, an average of 504 E. coli survived after treatment with the aqueous solution obtained in Comparative Example 5. This result shows that methyl lactic acid has bactericidal properties. Having bactericidal properties makes it an excellent peeling agent when used in treatments that lower the skin's barrier properties, such as peeling.

[0049] (Example 3) The acne bacteria elimination test used the acne bacteria, Cutibacterium acnes NBRC 107605. The test was performed in accordance with the "Disinfection and Decontamination Methods" in the 18th Edition of the Japanese Pharmacopoeia. The test bacteria were contacted with an agar medium and anaerobically cultured at 37°C for 48 hours. After that, physiological saline was used to adjust the bacterial count to 10 CFU / mL, and this was used as a test bacterial solution. Five mL of a methyl lactic acid aqueous solution prepared according to the composition ratios in Table 3 was dispensed into a test tube to serve as a test sample. Phosphate-buffered saline (PBS) was also used as a test sample. 0.05 mL of the test bacterial solution was inoculated into the test sample and allowed to stand at room temperature. 30 seconds after inoculation, a 10-fold dilution series of the test sample was prepared in soybean casein digest liquid medium supplemented with lecithin and polysorbate 80. The agar medium was inoculated and anaerobically cultured at 37°C for 3 to 5 days. After culturing, the formed colonies were counted and the number of viable bacteria was calculated. The acne bacteria removal rate was calculated from the number of viable bacteria before and after the test using the following formula: acne bacteria removal rate (%) = number of viable bacteria after test / number of viable bacteria before test × 100 Table 4 shows the acne bacteria removal rate when the methyl lactic acid aqueous solution was applied for 30 seconds, and the evaluation results evaluated according to the following criteria. acne bacteria removal rate: Rating A: 99% or more Rating B: 98% or more and less than 99% Rating C: 95% or more and less than 98% Rating D: less than 95% From Table 4, it was observed that when the methyl lactic acid was applied for 30 seconds, 99% or more of the acne bacteria were killed.

[0050] (Comparative Examples 6 to 9) The same procedure as in Example 3 was carried out using the compositions of Comparative Examples 6 to 9 in Table 3. The acne bacteria removal rate when each test sample was applied for 30 seconds is shown in Table 4. Table 4 shows that when lactic acid was used, 1% or more of the acne bacteria remained, when glycolic acid was used, 4% or more, when water was used, 75% or more, and when methyl lactic acid and glycolic acid were used in combination, 1% or more.

[0051] These results show that methyl lactic acid has a high antibacterial effect against acne bacteria, which are the bacteria that cause acne. A high antibacterial effect against acne bacteria means that acne can also be improved, making it an excellent peeling agent.

[0052]

[0053]

[0054] The peeling agent of the present invention contains methyl lactic acid as a main component, so that a peeling agent with a high concentration and a high pH can be obtained compared to other hydroxycarboxylic acids, and the peeling agent has low skin irritation, good control of peeling depth, and sufficient peeling depth can be obtained. According to a preferred embodiment of the present invention, the high concentration of acid does not penetrate deep into the skin, so there is no risk of systemic side effects, and only the keratin can be powerfully peeled off. Therefore, the peeling agent of the present invention can effectively remove wrinkles, age spots (pigmentation such as senile lentigo), and dullness, and can also improve oily skin.

Claims

1. A peeling agent for peeling the epidermis from the surface layer of the skin, comprising methyl lactic acid and water, The content of the methyl lactic acid is 0.1 to 70% by mass, and the content of the water is 99.9 to 30% by mass, based on the total amount of the methyl lactic acid and water, The peeling agent has a pH of 0.5 to 12.

2. The peeling agent according to claim 1 , further comprising a thickener.

3. 3. The peeling agent according to claim 2, wherein the content of the thickener is 0.01 to 5% by mass relative to the total amount of the peeling agent.

4. 2. The peeling agent according to claim 1, which has an acne bacteria removal rate of 99.0% or more after the peeling agent is added to an acne bacteria test solution and allowed to stand at room temperature for 30 seconds.

5. The peeling agent according to claim 1, which does not contain any hydroxycarboxylic acid other than methyl lactic acid.

6. A peeling method for peeling the epidermis of the skin from the surface layer, comprising the step of applying the peeling agent according to any one of claims 1 to 5 to the skin and peeling the epidermis of the skin from the surface layer.

7. 7. The peeling method according to claim 6, which is a cosmetic peeling method for reducing the appearance of at least one of wrinkles, fine lines, pigmentation marks, and scars.

8. 7. The peeling method according to claim 6, wherein the reduction rate of the stratum corneum in the skin after the peeling step is 35 to 50% when calculated by the following formula (1): (1) Stratum corneum reduction rate = (stratum corneum thickness when using water - stratum corneum thickness when using the peeling agent) / (stratum corneum thickness when using water) × 100 (%)