Bactericidal or virucidal compositions

Abstract

To provide a method that can effectively protect skin from bacteria or viruses, and has high safety to a human body.SOLUTION: A method for protecting skin from bacteria or viruses having a step of applying a composition containing one or more acid selected from a group consisting of lactic acid, pyruvic acid and urocanic acid or salt (A) thereof to skin, in which the amount of component (A) which is present as an acid type on a skin surface to which the composition is applied is 0.5 μg or more and 200 μg or less per skin 1 cm2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for protecting the skin from bacteria or viruses. [Background technology]

[0002] In households with infants and young children, the main route of infection is known to be when infants bring bacteria or viruses into the home from the outside, and households with children are thought to be particularly at high risk of contracting colds and influenza viruses. Recent studies have shown that contact infection is a common route of bacterial or viral infection in people's daily lives. Contact infection occurs primarily when hands come into contact with infected people, doorknobs, handles, tableware, toys, other household items, interior decorations, and other objects.

[0003] There is a need for a method to prevent bacterial or viral infections caused by contact in such everyday life. As a method for preventing contact infection of bacteria or viruses via hands, a method of applying an alcohol-based disinfectant to hands to disinfect them is known (see, for example, Patent Documents 1 and 2). However, for disinfectants applied to the skin in disinfection, it is desirable that they not only have a bactericidal effect but also be safe for the human body. In particular, there is a demand for a disinfection method that can be used safely by people with sensitive skin and young children. For example, the disinfectants and antiseptics described in Patent Documents 1 and 2 contain more than the effective amount of ethanol or cationic bactericides, which are highly irritating to the skin. Furthermore, when used as leave-on preparations that are applied to the skin, they are highly volatile, making it difficult to disinfect for long periods of time. As a result, these demands are not fully met at present. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-355506 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-155712 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have investigated a method for imparting a protective function against bacteria or viruses (hereinafter simply referred to as "barrier property") to hands. This method provides a continuous effect of preventing bacterial or viral infection, and can prevent contact infection even in environments where there is no hand-washing facility, such as when out and about. It is also advantageous in that it can prevent infection even when repeatedly coming into contact with an object that has bacteria or viruses attached. An object of the present invention is to provide a method that can effectively protect the skin from bacteria or viruses and is highly safe for the human body. [Means for solving the problem]

[0006] Through a comprehensive analysis of the components and properties of human skin, the inventors have found that the rate at which bacterial counts on the skin surface decrease is influenced by four factors: the amount of lactic acid, pyruvic acid, and urocanic acid present on the skin surface, the hydrogen ion exponent, temperature, and drying rate. They have also found that fingers, which contain particularly high amounts of lactic acid, pyruvic acid, and urocanic acid, prevent the proliferation of bacteria and viruses and are effective in preventing contact infection via hands, etc. Based on this knowledge, further research was conducted and it was discovered that by using lactic acid, pyruvic acid and urocanic acid, which are naturally present on the surface of human skin, as bactericidal and virucidal ingredients and applying these ingredients to the skin so that the amount of these ingredients present in their acid form (lactic acid, pyruvic acid, urocanic acid) rather than their dissociated form (lactic acid ions, pyruvic acid ions, urocanic acid ions) is within a specified range, it is possible to use ingredients derived from human skin to suppress the growth of bacteria and viruses on the skin surface, thereby maintaining hygienic skin. The present invention comprises a step of applying to the skin a composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid, and wherein the amount of component (A) present in an acid form on the skin surface to which the composition has been applied is determined so that the amount of component (A) present in an acid form is reduced by 1 cm of the skin. 2The present invention relates to a method for protecting the skin from bacteria or viruses, wherein the amount of the active ingredient is 0.5 μg or more and 200 μg or less per unit area. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method that can effectively protect the skin from bacteria or viruses using lactic acid, pyruvic acid, or urocanic acid, which is naturally present on the surface of human skin, and that is highly safe for the human body. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows the results of analyzing the organic acid composition on fingers by the method described in the Examples. [Figure 2] FIG. 1 is a schematic diagram showing the mechanism by which organic acids exert barrier properties on the surface of human skin. [Figure 3] FIG. 1 is a schematic diagram showing the mechanism by which the acid form of lactic acid passes through the cell membrane of bacteria or viruses, thereby exhibiting bactericidal or virucidal properties. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Methods for protecting the skin from bacteria or viruses] The method of the present invention for protecting skin from bacteria or viruses (hereinafter also referred to as "the method of the present invention") comprises the step of applying to the skin a composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid and urocanic acid, and wherein the amount of component (A) present in an acid form on the skin surface to which the composition has been applied is such that the amount of component (A) present in an acid form is within 1 cm of the skin. 2 The method is such that the concentration is between 0.5 μg and 200 μg per unit area. By virtue of the above constitution, the method of the present invention has good barrier properties against bacteria or viruses and is highly safe for the human body.

[0010] As used herein, "protecting skin from bacteria or viruses" encompasses the following concepts: (1) sterilizing or killing viruses using the skin surface to which the composition is applied; (2) preparing the skin to be immune to bacterial or viral transmission through the bactericidal or virucidal effects of the skin surface to which the composition is applied; (3) protecting the skin from bacteria or viruses and maintaining hygiene by applying the composition to the skin; and (4) enhancing the skin's defense against bacterial or viral infections on the skin surface to which the composition is applied. Furthermore, unlike techniques for sterilizing or killing viruses using ethanol or the like, the method of the present invention is particularly useful for leave-on preparations that are intended to remain on the skin surface, as the composition is more likely to remain on the skin surface and can provide a continuous bactericidal or virucidal effect on the skin surface. Furthermore, the use of lactic acid, pyruvic acid, and urocanic acid, which are naturally present on the human skin surface, is expected to suppress skin problems such as rashes on the skin surface to which the composition is applied.

[0011] As used herein, "component (A) existing in acid form" refers to component (A) that exists as lactic acid, pyruvic acid, and urocanic acid in the composition or on the skin surface to which the composition has been applied, and "component (A) that exists in dissociated form" refers to component (A) that exists as lactate ions, pyruvic acid ions, and urocanic acid ions in the composition or on the skin surface to which the composition has been applied.

[0012] The circumstances that led to the present invention will be described below. Lactic acid, pyruvic acid, and urocanic acid, which are components (A), are naturally present on the surface of human skin, for example, through supply from sweat glands. The present inventors conducted a comprehensive analysis of the components and properties of human fingers. Specifically, the organic acid composition on the fingers of 54 Japanese men and women in their 20s to 40s was analyzed using the method described in the Examples. Figure 1 shows the analysis results, which revealed that lactic acid was the most abundant (90% by mass), followed by pyruvic acid (5.7% by mass) and urocanic acid (3.4% by mass), accounting for more than 99% by mass of the total. Furthermore, it was found that individuals with higher amounts of lactic acid, pyruvic acid, and urocanic acid on their fingers were less likely to contract infectious diseases such as influenza. Figure 2 is a schematic diagram showing the mechanism by which organic acids exert barrier properties on the human skin surface. Based on the above findings, the present inventors predicted that organic acids contained in sweat, such as lactic acid, pyruvic acid, and urocanic acid, are responsible for the barrier function against bacteria, viruses, and the like on the human skin surface. The inventors then completed the present invention, believing that a method for protecting the skin from bacteria or viruses that is highly safe for the human body and that suppresses skin troubles due to skin irritation can be provided by supplementing the skin surface with component (A), which is a human skin-derived component, so as to replicate the fingers of a person who is less susceptible to infectious diseases.

[0013] The reason why the method of the present invention exhibits the above-mentioned effects is not clear, but is thought to be as follows: The presumed mechanism of action of the present invention will be explained below with reference to FIG. Figure 3 is a schematic diagram showing the mechanism by which the acid form of lactic acid passes through the cell membrane of bacteria or viruses, thereby manifesting bactericidal or virucidal properties. Lactic acid, which is one of the components (A), exists in aqueous solution in two forms: the acid form (CH3CH(OH)COOH) and the dissociated form (CH3CH(OH)COO -), but the acid form has no electric charge and is more easily taken up by bacteria or viruses, so the acid form exhibits higher barrier properties. Therefore, it is presumed that by adjusting the amount of the composition to be applied to the skin so that the amount of component (A) present in the acid form falls within a predetermined range, it is possible to impart barrier properties against bacteria or viruses even when the amount of component (A), a bactericidal and virucidal component, applied is small, and furthermore, skin irritation can be reduced.

[0014] The bacteria or viruses for which the method of the present invention provides barrier properties are not particularly limited as long as they are inactivated or killed by contact with acid, and it is believed that, for example, the microorganisms described in the Ministry of Health, Labor and Welfare's Guidelines for Infectious Disease Control in Nurseries can be applied. Specific examples of bacteria include gram-positive bacteria such as Bacillus anthracis, Mycobacterium tuberculosis, Streptococcus hemolyticus, Staphylococcus aureus, and Streptococcus pneumoniae, as well as gram-negative bacteria such as Francisella tularensis, Yersinia pestis, Brucella, Bacillus mallei, Vibrio cholerae, Salmonella enterica, Shigella, enterohemorrhagic Escherichia coli, and Bordetella pertussis. Examples of viruses include enveloped viruses such as arenaviruses, Ebola viruses, smallpox viruses, nairoviruses, Marburg viruses, coronaviruses, monkeypox viruses, betacoronaviruses, influenza viruses, respiratory syncytial viruses, herpes viruses, mumps viruses, varicella-zoster viruses, rubella viruses, and measles viruses, as well as non-enveloped viruses such as enteroviruses, adenoviruses, coxsackieviruses, noroviruses, and rotaviruses. In this example, Escherichia coli and Enterococcus faecalis are used as examples to evaluate bactericidal activity. However, these are microorganisms that can be ethically attached to the skin, or the evaluation method of attaching them to human skin is established in official test methods or academic papers, etc., and the bacteria or viruses targeted by the present invention are not limited to these.

[0015] <Composition> The composition used in the present invention contains one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid. (Component (A)) Component (A) used in the composition of the present invention is one or more acids selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid, or salts thereof. Component (A) acts as a barrier component against bacteria or viruses. Examples of salts of lactic acid, pyruvic acid, and urocanic acid include alkali metal salts of lactic acid or pyruvic acid, such as potassium salts and sodium salts; alkaline earth metal salts, such as calcium salts and magnesium salts; amine salts; ammonium salts, etc. Among these, from the viewpoints of improving barrier properties against bacteria or viruses and easy availability, one or more selected from the group consisting of alkali metal salts and alkaline earth metal salts of lactic acid, pyruvic acid, and urocanic acid are preferred, more preferably one or more selected from the group consisting of potassium salts, sodium salts, and calcium salts, and even more preferably one or more selected from the group consisting of potassium lactate, sodium lactate, and calcium lactate. From the viewpoint of improving the barrier properties against bacteria or viruses, component (A) is preferably lactic acid or a salt thereof, more preferably one or more selected from the group consisting of lactic acid, potassium lactate, sodium lactate, and calcium lactate, and even more preferably lactic acid.

[0016] The content of component (A) in the composition used in the present invention is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.8% by mass or more, still more preferably 3% by mass or more, and even more preferably 8% by mass or more, from the viewpoint of improving barrier properties against bacteria or viruses. Furthermore, from the viewpoint of suppressing skin troubles due to skin irritation, it is preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less. The content of component (A) in the composition is preferably 0.1 to 35% by mass, more preferably 0.3 to 30% by mass, even more preferably 0.8 to 30% by mass, still more preferably 3 to 20% by mass, and even more preferably 8 to 15% by mass. In this specification, the "content of component (A)" means the amount converted into lactic acid, pyruvic acid, and urocanic acid.

[0017] The content of component (A) in an acid form in the composition used in the present invention is preferably 0.005% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of improving barrier properties against bacteria or viruses. Furthermore, from the viewpoint of suppressing skin troubles due to skin irritation, it is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less, and even more preferably 5% by mass or less. The content of component (A) in the composition is preferably 0.005 to 20% by mass, more preferably 0.05 to 10% by mass, even more preferably 0.5 to 8% by mass, and even more preferably 1 to 5% by mass.

[0018] From the viewpoint of improving barrier properties against bacteria or viruses, the molar ratio of component (A) present in acid form to the total of component (A) present in acid form and component (A) present in dissociated form in the composition [acid form / (acid form+dissociated form)] is preferably 0.0001 or more, more preferably 0.01 or more, even more preferably 0.1 or more, and even more preferably 0.3 or more. Furthermore, from the viewpoint of suppressing skin troubles due to skin irritation, it is preferably 0.995 or less, more preferably 0.9 or less, even more preferably 0.8 or less, and even more preferably 0.6 or less. The molar ratio [acid form / (acid form+dissociated form)] in the composition is preferably 0.0001 to 0.995, more preferably 0.01 to 0.9, even more preferably 0.1 to 0.8, and even more preferably 0.3 to 0.6. The above molar ratio can be controlled by adjusting the pH of the composition using a pH adjuster or the like, and specifically, can be calculated by the method described in the Examples.

[0019] The composition used in the present invention preferably further contains water from the viewpoints of dissolving component (A) and facilitating application to the skin surface. The water content in the composition can be appropriately selected depending on the amount of component (A) used, but is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 60% by mass or more, and even more preferably 85% by mass or more, and is preferably 99.9% by mass or less, more preferably 98% by mass or less, even more preferably 95% by mass or less, and even more preferably 92% by mass or less. The water content in the composition is preferably 10 to 99.9% by mass, more preferably 30 to 98% by mass, even more preferably 60 to 95% by mass, and even more preferably 85 to 92% by mass.

[0020] From the viewpoint of obtaining the effects of the present invention, the total content of component (A) and water in the composition is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and may be 100% by mass.

[0021] In addition to the above, the composition may contain other components as needed, such as an acid other than component (A) or a salt thereof, a surfactant, a thickener, a pH adjuster, an ultraviolet absorber, an antioxidant, a preservative, an antiperspirant, a fragrance, a moisturizer, a plant extract, or a whitening component. Among the above, it is preferable to include a surfactant in the composition from the viewpoint of improving the stability of the composition, improving the shape retention of the composition, allowing the composition to remain on the skin longer upon application, and further improving the barrier properties against bacteria or viruses. Examples of surfactants include nonionic surfactants and anionic surfactants, with nonionic surfactants being preferred from the viewpoint of safety.

[0022] When a surfactant is used, the content in the composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, and even more preferably 0.3% by mass or more, from the viewpoint of improving the barrier property against bacteria or viruses, and is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less, from the viewpoint of suppressing skin troubles due to skin irritation. The content of the surfactant in the composition is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, even more preferably 0.1 to 3% by mass, and even more preferably 0.3 to 2% by mass.

[0023] The composition is distinguished from disinfectant compositions containing cationic disinfectants, etc., in that it is a composition using component (A) as a barrier component against bacteria or viruses. From this viewpoint, and from the viewpoint of suppressing skin troubles due to skin irritation, the content of the cationic disinfectant in the composition is preferably 15% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, still more preferably 0.1% by mass or less, and most preferably substantially 0% by mass.

[0024] From the viewpoint of suppressing skin troubles due to skin irritation, the pH of the composition used in the present invention is preferably 1.5 or higher, more preferably 3.0 or higher, even more preferably 3.2 or higher, still more preferably 3.5 or higher, and even more preferably 3.7 or higher. Furthermore, from the viewpoint of improving barrier properties against bacteria or viruses, the pH is preferably 7.0 or lower, more preferably 6.0 or lower, even more preferably 5.5 or lower, still more preferably 5.0 or lower, still more preferably 4.5 or lower, and even more preferably 4.2 or lower. The pH of the composition is preferably 1.5 to 7.0, more preferably 1.5 to 6.0, even more preferably 3.0 to 5.5, still more preferably 3.2 to 5.0, still more preferably 3.5 to 4.5, and even more preferably 3.7 to 4.2. The pH is measured at 25° C., and can be measured by the method described in the Examples.

[0025] The form of the composition is not particularly limited, and may be, for example, a solid, liquid, gel, or cream. From the viewpoint of ease of application to the skin, a gel or cream form is preferable. The composition may be in the form of an emulsion composition, and the emulsion composition may be either an oil-in-water emulsion composition or a water-in-oil emulsion composition.

[0026] The dosage form of the composition is not particularly limited, and examples thereof include stick formulations containing a solid composition; roll-on or spray formulations filled with a liquid composition; formulations in which a liquid, gel, or cream composition is filled in a bottle, tube, dispenser-type container, or the like; and sheet products impregnated with the composition.

[0027] <Composition application process> The method of the present invention includes a step of applying to the skin a composition containing the component (A). The method of applying the composition to the skin can be selected depending on the formulation of the composition, the area to be applied, etc. For example, the composition can be applied by painting or spraying onto the skin. The body part to which the composition is applied is not particularly limited, and it can be applied to any body part, such as the fingers, upper arms, lower legs, neck, trunk, etc. From the viewpoint of blocking the route of infection and transmission of bacteria and viruses through human-to-human and object-to-human contact, it is preferable to apply it to the hands and fingers, which are frequently in contact with public objects and one's own nose and mouth in daily life.

[0028] In this step, the amount of the composition applied is set so that the amount of component (A) present in the acid form in the composition is such that it covers 1 cm of skin. 2 Within this range, good barrier properties against bacteria or viruses are exhibited, skin irritation is low, skin troubles can be suppressed, and safety to the human body is high. The amount of the composition to be applied is determined based on the amount of component (A) present in the acid form in the composition, in order to improve the barrier properties against bacteria or viruses, per 1 cm of skin. 2It is more preferably 0.5 μg or more, even more preferably 2 μg or more, even more preferably 5 μg or more, even more preferably 20 μg or more, and even more preferably 30 μg or more. From the viewpoint of suppressing skin troubles due to skin irritation, it is preferably 100 μg or less, more preferably 80 μg or less, even more preferably 60 μg or less, and even more preferably 45 μg or less. The amount of the composition to be applied is preferably 0.05 to 200 μg, more preferably 0.5 to 200 μg, even more preferably 2 to 100 μg, even more preferably 5 to 80 μg, even more preferably 20 to 60 μg, and even more preferably 30 to 45 μg, in terms of the amount of component (A) present in the acid form in the composition. The term "the amount of component (A) present in the acid form in the composition" used herein refers to the amount of component (A) in the acid form contained in the composition before it is applied to the skin.

[0029] In this step, the amount of component (A) present in an acid form on the skin surface to which the composition is applied is adjusted to 1 cm of skin. 2 The composition is applied so that the amount is 0.5 μg or more and 200 μg or less per unit area. Within this range, good barrier properties against bacteria or viruses are exhibited, skin irritation is low, skin troubles can be suppressed, and the composition is highly safe for the human body. The amount of component (A) present in an acid form on the skin surface to which the composition is applied is determined based on the amount of component (A) present in an acid form on 1 cm of the skin from the viewpoint of improving the barrier property against bacteria or viruses. 2 The amount of component (A) present in an acid form on the surface of the skin to which the composition is applied is preferably 0.8 μg or more, more preferably 5 μg or more, even more preferably 10 μg or more, and even more preferably 30 μg or more, per 1 cm of skin. From the viewpoint of suppressing skin troubles due to skin irritation, the amount is preferably 92 μg or less, more preferably 80 μg or less, even more preferably 60 μg or less, and even more preferably 43 μg or less. The amount of component (A) present in an acid form on the surface of the skin to which the composition is applied is preferably 0.8 μg or more, more preferably 5 μg or more, even more preferably 10 μg or more, and even more preferably 30 μg or more, per 1 cm of skin. 2 The amount is 0.5 to 200 μg per unit area, preferably 0.8 to 92 μg, more preferably 5 to 80 μg, even more preferably 10 to 60 μg, and still more preferably 30 to 43 μg. The "amount of component (A) present in acid form on the skin surface to which the composition has been applied" refers to the total amount of acid-form component (A) derived from the composition and acid-form component (A) naturally present on the skin surface at the time the composition has been applied, and can be determined specifically by the method described in the Examples.

[0030] The molar ratio of component (A) present in acid form to the total of component (A) present in acid form and component (A) present in dissociated form on the skin surface to which the composition is applied [acid form / (acid form + dissociated form)] is preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.20 or more, and even more preferably 0.30 or more, from the viewpoint of improving barrier properties against bacteria or viruses. Furthermore, from the viewpoint of suppressing skin troubles due to skin irritation, it is preferably 0.92 or less, more preferably 0.80 or less, even more preferably 0.60 or less, and even more preferably 0.50 or less. The molar ratio [acid form / (acid form + dissociated form)] on the skin surface to which the composition is applied is preferably 0.05 to 0.92, more preferably 0.10 to 0.80, even more preferably 0.20 to 0.60, and even more preferably 0.30 to 0.50. The molar ratio [acid type / (acid type+dissociated type)] takes into account both the component (A) derived from the composition and the component (A) naturally present on the skin surface at the time of application of the composition. The molar ratio can be determined specifically by the method described in the Examples.

[0031] From the viewpoint of suppressing skin troubles due to skin irritation, the pH of the skin surface after application of the composition is preferably 2.0 or higher, more preferably 3.0 or higher, even more preferably 3.5 or higher, and even more preferably 3.7 or higher. From the viewpoint of improving barrier properties against bacteria or viruses, the pH is preferably 6.0 or lower, more preferably 5.5 or lower, even more preferably 5.0 or lower, and even more preferably 4.5 or lower. The pH of the skin surface after application of the composition is preferably 2.0 to 6.0, more preferably 3.0 to 5.5, even more preferably 3.5 to 5.0, and even more preferably 3.7 to 4.5. The pH of the skin surface is a value measured at the environmental temperature to which the method of the present invention is applied, and specifically, can be measured by the method described in the Examples.

[0032] In the method of the present invention, after applying the composition to the skin, it is preferable to leave the composition on the skin surface without removing it by rinsing with water, etc. This is because when the composition is used as a leave-on preparation and the barrier component (A) remains on the skin surface, it can impart barrier properties against bacteria or viruses. The composition may be applied to the skin after washing the skin in advance with water, soap, body soap, hand soap, etc., or may be applied to unwashed skin. After washing, components originally present in the skin, such as lactic acid, are washed away, and the skin's barrier properties against bacteria and viruses present in the environment are reduced. Therefore, it is more preferable to carry out the method of the present invention by applying the composition to the skin after washing.

[0033] The method of the present invention is intended to provide a method for protecting the skin from bacteria or viruses, which has an excellent barrier property against bacteria or viruses and further suppresses skin troubles due to skin irritation, and includes a step of applying to the skin a composition containing lactic acid or a salt thereof (A), and the amount of component (A) present in an acid form on the skin surface to which the composition has been applied is determined so that the amount of component (A) present in an acid form is reduced per 1 cm of the skin. 2 Preferably, the method is such that the amount of the ion exchange reaction is 0.8 μg or more and 92 μg or less per unit time.

[0034] From the viewpoint of providing a method that has superior barrier properties against bacteria or viruses and further suppresses skin troubles due to skin irritation, the method of the present invention preferably comprises the step of applying to the skin a bactericidal or virucidal composition that contains lactic acid or a salt thereof (A), in which the content of component (A) existing in acid form is 0.05% by mass or more and 10% by mass or less, and in which the molar ratio of component (A) existing in acid form to the total of component (A) existing in acid form and component (A) existing in dissociated form [acid form / (acid form+dissociated form)] is 0.01 to 0.9.

[0035] The present invention also provides a method for protecting skin from bacteria or viruses, which comprises the step of applying to the skin a bactericidal or virucidal composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid, wherein the content of component (A) in an acid form is 0.005% by mass or more and 20% by mass or less. The component (A), the content of the component (A) present in the acid form in the composition, the step of applying the composition, and preferred embodiments thereof are the same as those described above.

[0036] Bactericidal or virucidal compositions The present invention provides a bactericidal or virucidal composition for application to the skin, which contains one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid and urocanic acid, and wherein the amount of component (A) present in an acid form on the skin surface to which the composition has been applied is such that the amount of component (A) present in an acid form is less than 1 cm of skin. 2 The bactericidal or virucidal composition has a concentration of 0.5 μg or more and 200 μg or less per unit area. Component (A), the amount of component (A) present in the acid form, and preferred embodiments thereof are the same as those described above.

[0037] [How to improve your defenses against infection] The present invention relates to a method for enhancing the ability of the skin to defend itself against bacterial or viral infection, which comprises the step of applying to the skin a composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid, and wherein the amount of component (A) present in an acid form on the skin surface to which the composition has been applied is 100% or more per 1 cm of the skin. 2 Also provided is a method in which the concentration is 0.5 μg or more and 200 μg or less per unit area. Component (A), the amount of component (A) present in acid form, the process for applying the composition, and preferred embodiments thereof are the same as those described above.

[0038] In addition to the above-described embodiments, the present invention also discloses the following embodiments. <1> A method for protecting the skin from bacteria or viruses, comprising: The method includes a step of applying to the skin a composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid; The amount of component (A) present in an acid form on the skin surface to which the composition is applied is 2 The method is such that the concentration is 0.5 μg or more and 200 μg or less per unit area. <2> The amount of component (A) present in an acid form on the skin surface to which the composition is applied is determined by the following formula: 2 Preferably, the amount is 0.8 μg or more, more preferably 5 μg or more, even more preferably 10 μg or more, still more preferably 30 μg or more, and preferably 92 μg or less, more preferably 80 μg or less, even more preferably 60 μg or less, still more preferably 43 μg or less, <1> The method described below. <3> The amount of the composition applied is such that the amount of component (A) present in the acid form in the composition is 2 per 1000 mg / kg body weight, preferably 0.05 μg or more, preferably 0.5 μg or more, more preferably 2 μg or more, even more preferably 5 μg or more, still more preferably 20 μg or more, still more preferably 30 μg or more, and 200 μg or less, preferably 100 μg or less, more preferably 80 μg or less, still more preferably 60 μg or less, still more preferably 45 μg or less, <1> or <2> The method described below. <4> The salts of lactic acid, pyruvic acid, and urocanic acid in component (A) are alkali metal salts, alkaline earth metal salts, amine salts, or ammonium salts of lactic acid or pyruvic acid, preferably one or more selected from the group consisting of alkali metal salts and alkaline earth metal salts of lactic acid, pyruvic acid, and urocanic acid, more preferably one or more selected from the group consisting of potassium salts, sodium salts, and calcium salts of lactic acid, pyruvic acid, and urocanic acid, even more preferably one or more selected from the group consisting of potassium lactate, sodium lactate, and calcium lactate. <1> ~ <3> 10. The method according to claim 9, wherein <5> Component (A) is lactic acid or a salt thereof, preferably one or more selected from the group consisting of lactic acid, potassium lactate, sodium lactate, and calcium lactate, more preferably lactic acid; <1> ~ <4> 10. The method according to claim 9, wherein <6> the molar ratio of component (A) present in acid form to the sum of component (A) present in acid form and component (A) present in dissociated form on the skin surface to which the composition is applied [acid form / (acid form+dissociated form)] is preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.20 or more, still more preferably 0.30 or more, and is preferably 0.92 or less, more preferably 0.80 or less, even more preferably 0.60 or less, and still more preferably 0.50 or less; <1> ~ <5> 10. The method according to claim 9, wherein <7> In the composition, the molar ratio of component (A) present in acid form to the total of component (A) present in acid form and component (A) present in dissociated form [acid form / (acid form+dissociated form)] is preferably 0.0001 or more, more preferably 0.01 or more, even more preferably 0.1 or more, still more preferably 0.3 or more, and is preferably 0.995 or less, more preferably 0.9 or less, even more preferably 0.8 or less, and still more preferably 0.6 or less. <1> ~ <6> 10. The method according to claim 9, wherein <8> The content of component (A) in the composition is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.8% by mass or more, still more preferably 3% by mass or more, still more preferably 8% by mass or more, and is preferably 35% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, and still more preferably 15% by mass or less. <1> ~ <7> 10. The method according to claim 9, wherein <9> the composition further contains water, and the content of water in the composition is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 60% by mass or more, still more preferably 85% by mass or more, and is preferably 99.9% by mass or less, more preferably 98% by mass or less, even more preferably 95% by mass or less, and still more preferably 92% by mass or less; <1> ~ <8> 10. The method according to claim 9, wherein <10> the composition further contains a surfactant, and the content of the surfactant in the composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, still more preferably 0.3% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and still more preferably 2% by mass or less; <1> ~ <9> 10. The method according to claim 9, wherein

[0039] <11> The surfactant is a nonionic surfactant. <10> The method described below. <12> the total content of component (A) and water in the composition is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more, and 100% by mass or less; <1> ~ <11> 10. The method according to claim 9, wherein <13> The pH of the composition is preferably 2.0 or more, more preferably 3.0 or more, even more preferably 3.2 or more, still more preferably 3.5 or more, still more preferably 3.7 or more, and preferably 7.0 or less, more preferably 6.0 or less, even more preferably 5.5 or less, still more preferably 5.0 or less, still more preferably 4.5 or less, still more preferably 4.2 or less. <1> ~ <12> 10. The method according to claim 9, wherein <14> The content of the cationic disinfectant in the composition is preferably 15% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, still more preferably 0.1% by mass or less, and is substantially 0% by mass. <1> ~ <13> 10. The method according to claim 9, wherein <15> The body part to which the composition is applied is a finger, an upper arm, a lower leg, a neck, or a trunk, preferably a finger; <1> ~ <14> 10. The method according to claim 9, wherein <16> The pH of the skin surface after application of the composition is preferably 2.0 or higher, more preferably 3.0 or higher, even more preferably 3.5 or higher, still more preferably 3.7 or higher, and preferably 6.0 or lower, more preferably 5.5 or lower, even more preferably 5.0 or lower, still more preferably 4.5 or lower. <1> ~ <15> 10. The method according to claim 9, wherein <17> After applying the composition to the skin, the composition is not removed but is allowed to remain on the skin surface. <1> ~ <16> 10. The method according to claim 9, wherein <18> applying the composition to uncleansed skin; <1> ~ <17> 10. The method according to claim 9, wherein <19> applying the composition to cleansed skin; <1> ~ <17> 10. The method according to claim 9, wherein <20> Use of a composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid and urocanic acid, wherein the amount of component (A) present in an acid form on the skin surface is adjusted to 1 cm of skin. 2 Apply to the skin so that the dose is no less than 0.5 μg and no more than 200 μg per dose.

[0040] <21> A method for applying to the skin a composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid, wherein the amount of component (A) present in an acid form on the skin surface to which the composition has been applied is 1 cm , and 2 The method is to apply the method so that the amount is 0.5 μg or more and 200 μg or less per unit area. <22> A method for protecting the skin from bacteria or viruses, comprising: The method comprises the step of applying to the skin a bactericidal or virucidal composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid, wherein the content of component (A) in an acid form is 0.005% by mass or more and 20% by mass or less. <23> A bactericidal or virucidal composition for application to the skin, which contains one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid and urocanic acid, and wherein the amount of component (A) present in an acid form on the surface of the skin to which the composition is applied is 100% or more per 1 cm of skin. 2 A bactericidal or virucidal composition having a bactericidal activity of 0.5 μg or more and 200 μg or less per 1000 μg of the composition. <24> A method for enhancing the skin's ability to defend against infection, comprising: The method includes a step of applying to the skin a composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid; The amount of component (A) present in an acid form on the skin surface to which the composition is applied is 2 The method is such that the concentration is 0.5 μg or more and 200 μg or less per unit area. <25> A method for applying a bactericidal or virucidal composition, comprising the step of applying to the skin a bactericidal or virucidal composition which contains one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid and urocanic acid, and in which the content of component (A) in an acid form is 0.005% by mass or more and 20% by mass or less. [Example]

[0041] The present invention will be described below with reference to examples, but the present invention is not limited to the scope of the examples. In the examples, various measurements and evaluations were carried out by the following methods.

[0042] (Analysis of organic acid composition on human fingers) Three pieces of filter paper, each containing 60 μL of pure water, were attached to the palms of 54 subjects for 5 minutes, and the water-soluble components on the palms were collected. The filter papers were dried using nitrogen spray, and then pure water was added again and ultrasonicated to extract the water-soluble components. The supernatant was then collected by centrifugation, and the organic acid components in the supernatant were identified and quantified using LC / MS. The organic acid composition shown in the pie chart in Figure 1 represents the average organic acid composition on the palms of 54 Japanese men and women in their 20s to 40s.

[0043] (pH) The pH of the composition was measured at 25° C. using a 6367-10D electrode (Horiba, Ltd.). The pH of the skin surface (palm) was measured using a Skin-pH-Meter PH905 electrode (Courage+Khazaka).

[0044] (Mole ratio of component (A) [acid type / (acid type + dissociated type)]) The molar ratio of component (A) in the composition used and on the skin surface after application of the composition was calculated using the following formula. The acid type is designated as "HA" and the dissociated type is designated as "A - " is written as ". pH = pKa + log(A - / HA) log(A - / HA) = pH - pKa A - / HA=10^(pH-pKa) A - = 10^(pH-pKa) × HA From the above, the molar ratio of the acid form [acid form / (acid form + dissociated form)] is HA / (HA+A - )=HA / (HA+10^(pH-pKa)×HA) =1 / (1+10^(pH-pKa)) Here, when lactic acid is used as component (A) (pKa=3.86), Molar ratio [lactic acid / (lactic acid + lactate ion)] = 1 / (1 + 10^(x-3.86)) (x represents the pH of the composition or the pH of the skin surface.)

[0045] Examples 1 to 10 (bactericidal evaluation) (Preparation of sterilizing composition) Lactic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to purified water and mixed to prepare an aqueous lactic acid solution. Next, the pH (25°C) of the aqueous lactic acid solution was adjusted using a 48% NaOH solution to the value shown in Table 1, and then purified water was added so that the final concentration of lactic acid was the "concentration of component (A) in the composition" shown in Table 1, thereby preparing a sterilization composition. (Preparation of bacterial solution) For the evaluation of bactericidal activity, bacterial suspensions of Escherichia coli and Enterococcus faecalis prepared by the following method were used. The Escherichia coli strain used was NBRC3301, and the enterococcus strain used was NBRC3181. These bacteria were cultured in LB liquid medium, and the bacterial cells were collected by centrifugation and then adjusted to OD600 = 10 using pure water.

[0046] (Bactericidal evaluation) The subjects' hands were washed with "Biore u Rg" (Kao Corporation), then rinsed with tap water for 30 seconds and then with purified water for 10 seconds. After waiting for 1 to 5 minutes, a fixed amount (3 μL / 3 cm) of the prepared sterilizing composition was applied to the palm of the hand. 2 ), and then left to dry for 3 minutes. At this time, the pH of the skin surface at the site where the sterilizing composition was applied was measured by the above-mentioned method, and from this pH value, the molar ratio of lactic acid to the total of lactic acid and lactate ions [lactic acid / (lactic acid + lactate ions)] on the skin surface after application of the composition was calculated using the above-mentioned formula. Next, a fixed amount (3 μL / 3 cm ) of the Escherichia coli or enterococcus bacterial solution prepared by the above method was applied to the area of ​​the palm where the sterilizing composition had been applied. 2 After leaving it to stand for 3 minutes, the applied bacterial solution was collected using two swabs, and the number of surviving bacteria was measured using an incubation reader "HiTS" (manufactured by Synix Co., Ltd.) according to the method described below, to confirm the reduction in the number of bacteria (number of surviving bacteria / initial number of live bacteria). [Measurement of reduction in bacterial count] The collected bacterial solution was cultured at 37°C in an incubation reader "HiTS," and the absorbance (turbidity) at a wavelength of 600 nm was measured over time to create a growth curve of the viable bacterial count in the bacterial solution. At the same time, a bacterial solution with a known viable bacterial count was serially diluted, and similarly cultured and a growth curve was created, creating a calibration curve of the time it took to reach a certain turbidity versus the viable bacterial count. From this calibration curve, the number of viable bacteria in the collected bacterial solution was estimated, and the reduction in the bacterial count was confirmed. The degree of reduction in the number of bacteria was calculated as the -log value of the reduction in the number of bacteria, and is shown in Table 1. If the "-log (reduction in the number of bacteria)" value for E. coli was 1.5 or higher, it was determined that sufficient bactericidal activity was obtained.

[0047] Comparative Example 1 A fixed amount of pure water (30 μL / 3 cm) was placed on the palm of the subject's hand. 2 ), and was applied uniformly and pipetted several times. At this time, the pH of the skin surface at the site where the pure water was applied was measured using the above-mentioned method. Thereafter, the solution on the palm was collected, and the total concentration of lactic acid and lactate ions was measured using Lactate Pro (manufactured by Arkray, Inc.). Next, the total amount of lactic acid and lactate ions per unit area was calculated from the volume of pure water used and the application area, and the molar ratio of lactic acid to the total amount of lactic acid and lactate ions [lactic acid / (lactic acid + lactate ions)] on the skin surface after application of the composition was calculated using the above-mentioned calculation formula from the pH of the skin surface. The subsequent steps were carried out in the same manner as in Examples 1 to 10, and the bactericidal activity against Escherichia coli was evaluated. The results are shown in Table 1.

[0048] [Table 1] [Industrial Applicability]

[0049] According to the present invention, it is possible to provide a method that can effectively protect the skin from bacteria or viruses using lactic acid, pyruvic acid, or urocanic acid, which are naturally present on the surface of human skin, and that is highly safe for the human body.

Claims

1. A composition containing one or more acids or salts thereof (A) selected from the group consisting of lactic acid, pyruvic acid, and urocanic acid, The amount of component (A) present in an acid form on the skin surface to which the composition is applied is ２ per unit of blood is 30 μg or more and 200 μg or less, and A bactericidal or virucidal composition to be applied to the skin surface so that the molar ratio of component (A) present in acid form to the sum of component (A) present in acid form and component (A) present in dissociated form on the skin surface to which the composition is applied [acid form / (acid form+dissociated form)] is 0.1 or more and 0.92 or less.

2. 2. The bactericidal or virucidal composition according to claim 1, wherein the content of component (A) in the composition is 0.1% by mass or more and 35% by mass or less.

3. 3. A bactericidal or virucidal composition according to claim 1, wherein the content of the cationic bactericide in the composition is 15% by weight or less.

4. 4. A bactericidal or virucidal composition according to any one of claims 1 to 3, for application to the surface of the skin so that the pH of the skin surface after application of the composition is 2.0 or higher and 4.5 or lower.

5. A bactericidal or virucidal composition according to any one of claims 1 to 4, for applying the composition to cleansed skin or for applying the composition to uncleansed skin.

6. A bactericidal or virucidal composition described in any one of claims 1 to 5, which is a leave-on formulation.

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