Methods of classifying skin

Abstract

By applying a structural analysis approach to stratum corneum samples taken from humans, the barrier function of the skin at any given location can be measured, and the type of skin barrier function, which differs depending on the ambient temperature and humidity, can be determined. [Solution] Based on the results of structural analysis of intercellular lipids or keratinocyte properties of stratum corneum collected from the skin of multiple individuals, and the corresponding values ​​of barrier properties based on the permeability of indicator substances in living skin kept in a low humidity environment, an axis of high and low barrier properties of the stratum corneum in a low humidity environment is obtained. Similarly, an axis of high and low barrier properties of the stratum corneum in a high humidity environment is obtained when it is kept in a high humidity environment. Then, structural analysis is performed on the stratum corneum collected from the skin of a subject when it is kept in the low humidity environment, and structural analysis is performed when it is kept in the high humidity environment. The barrier properties of the subject's skin are then classified according to the axes of high and low barrier properties of the stratum corneum in a low humidity environment and the axes of high and low barrier properties of the stratum corneum in a high humidity environment.

Description

[Technical Field]

[0001] This invention relates to a method for classifying skin barrier properties, which classifies how skin barrier properties change depending on ambient temperature and humidity.

[0002] The skin's barrier function is a characteristic of the skin that protects against the effects of external factors on the skin's surface, superficial layer, and internal layers. It is known that keeping the skin moist by wearing masks, diapers, rubber gloves, etc., affects the skin's barrier function and can lead to skin problems.

[0003] In this regard, it has been reported that mask wearers are aware of changes in their skin condition, such as roughness, dryness, and itching, regardless of the season, and are more aware of changes in their skin condition, such as breakouts, acne, and stickiness, in the summer (Non-Patent Literature 1).

[0004] Patent Document 1 describes that when moisture is applied to the skin, the thickness of the stratum corneum increases, and furthermore, the microstructure of the skin changes, forming a pore-like structure, which increases the permeability of indicator substances in the skin, that is, the barrier function of the skin decreases, and therefore, the effect of the test substance on the barrier function of the skin can be evaluated based on an image of the pore-like structure when the test substance is in contact with the skin.

[0005] Furthermore, as a method of providing skincare advice that takes living environment into consideration, it is known to use a database that links living environment factors such as temperature and humidity with the level of skin irritation and advice information (Patent Document 2).

[0006] However, considering that some people experience skin or lip irritation from wearing masks while others do not, it is difficult to predict how the barrier function of a subject's skin and lips will change depending on the ambient temperature and humidity. Therefore, it is not possible to uniformly advise on cosmetics or skincare methods that are effective in improving a subject's skin barrier function based on ambient temperature and humidity.

[0007] In contrast, the skin's barrier function is measured by keeping the arm in a constant temperature and humidity chamber adjusted to a predetermined temperature and humidity for a predetermined time, and measuring the permeability of indicator substances such as methyl nicotinate. The skin's barrier function is then categorized into the following four types based on the level of ambient humidity: (i) Those with low barrier properties in both low-humidity and high-humidity environments, (ii) Those with low barrier properties in low humidity environments and high barrier properties in high humidity environments, (iii) Those that have high barrier properties in low humidity and high humidity environments, (iv) Materials that have high barrier properties in low humidity environments and low barrier properties in high humidity environments. It has been proposed to classify cosmetics into categories and recommend cosmetics to customers according to these classifications (Patent Document 3).

[0008] However, the method for classifying skin barrier properties described in Patent Document 3 requires the subject's skin to be kept under constant temperature and humidity conditions for about 30 minutes in order to measure the skin barrier properties at a predetermined temperature and humidity. This places a significant burden on the subject, and the skin area is limited to the arm or other areas that can be placed in the constant temperature and humidity chamber. For example, it cannot be used to study skin on the head, face, or delicate areas. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 6326558 [Patent Document 2] WO2018 / 216678 publication [Patent Document 3] Japanese Patent Publication No. 2024-52277 [Non-patent literature]

[0010] [Non-Patent Document 1] Cosmetic Stage 16(4),6-10,2022 [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] With respect to the above prior art, the problem of the present invention is to alternatively apply various structural analysis approaches such as infrared spectroscopic analysis to the stratum corneum collected from humans, instead of the conventional method of measuring the skin barrier property based on the permeability of the indicator substance, so as to measure the skin barrier property of any site and be able to determine the types of skin barrier properties that vary depending on the environmental temperature and humidity.

Means for Solving the Problem

[0012] The present inventor maintained the stratum corneum collected from the skin (hereinafter also referred to as a stratum corneum sample) in a low humidity environment or a high humidity environment, and then performed a structural analysis on the properties of the intercellular lipids and keratinocytes constituting the stratum corneum sample that were expected to be related to the barrier property. When the analysis results were correlated with the measured values of the barrier property based on the permeability of the indicator substance in the skin of the living body maintained in a low humidity environment or a high humidity environment, it was found that there were results corresponding to the high or low barrier property due to the penetration of the indicator substance in the skin of the living body both in the structural analysis results of the stratum corneum sample maintained in a low humidity environment and in the structural analysis results of the stratum corneum sample maintained in a high humidity environment. The present invention was conceived by finding that the skin barrier property can be classified by using both the barrier property of the stratum corneum sample maintained in a low humidity environment and the barrier property of the stratum corneum sample maintained in a high humidity environment.

[0013] That is, the present invention relates to the stratum corneum collected from the skin of a plurality of people, At a temperature of 0°C or higher and 45°C or lower, it is the result of a structural analysis of the properties of intercellular lipids or keratinocytes maintained in a low humidity environment with a humidity of 30%RH or lower, based on which is corresponding to the measured value of the barrier property due to the permeability of the indicator substance in the skin of the living body maintained in the low humidity environment, and the axis of the high or low barrier property of the stratum corneum in the low humidity environment, At a temperature of 0°C or higher and 45°C or lower, it is the result of a structural analysis of the properties of intercellular lipids or keratinocytes maintained in a high humidity environment with a humidity of 70%RH or higher, based on which is corresponding to the measured value of the barrier property due to the permeability of the indicator substance in the skin of the living body maintained in the high humidity environment, and the axis of the high or low barrier property of the stratum corneum in the high humidity environment are obtained, For the stratum corneum collected from the skin of a subject, perform a structural analysis related to the axis of the level of the barrier property of the intercellular lipids or keratinocytes maintained in the low humidity environment, and perform a structural analysis related to the axis of the level of the barrier property of the intercellular lipids or keratinocytes maintained in the high humidity environment. Provide a skin classification method for classifying the barrier property of a subject's skin based on the axis of the level of the barrier property of the stratum corneum in a low humidity environment and the axis of the level of the barrier property of the stratum corneum in a high humidity environment.

[0014] The present invention also relates to a database in which the type of the barrier property of the skin classified by the above classification method is associated with information on cosmetics, makeup methods, skin care methods, or hair care methods suitable for improving the barrier property of the skin of that type, and an arithmetic device that outputs information on cosmetics, makeup methods, skin care methods, or hair care methods associated with the type when the type of the barrier property of the skin is input using the database, and provides a skin barrier property care system equipped with the arithmetic device.

Effects of the Invention

[0015] According to the skin classification method of the present invention, since it is only necessary to hold the stratum corneum collected from the skin of the subject in a low humidity environment or a high humidity environment, it is not necessary for the subject to put a part of the living body such as his or her own arm into a thermo-hygrostat in order to measure the barrier property of the skin in a low humidity environment or a high humidity environment. Therefore, the burden on the subject when examining the type of the barrier property of the subject's skin is greatly reduced. In addition, there is no limitation on the skin site for examining the type of the barrier property, and for example, the skin of the head, face, neck, back, abdomen, legs, delicate zones, etc. can also be targeted.

[0016] In addition, it is not necessary to measure the barrier property of the subject's skin by the permeability of an indicator substance such as methyl nicotinate, and it can be easily measured by a method such as infrared spectroscopic analysis.

[0017] Furthermore, since it becomes clear what properties of intercellular lipids or keratinocytes need to be improved to enhance the skin barrier function of the subject, it becomes easier to select an effective agent for improving the skin barrier function. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is an explanatory diagram illustrating the types of skin barrier properties, represented by axes of skin barrier properties in low-humidity environments and skin barrier properties in high-humidity environments. [Figure 2] Figure 2 shows the relationship between environmental humidity and the erythema score of living skin, as well as the relationship between environmental humidity and the density of intercellular lipids in a stratum corneum sample, and the relationship between environmental humidity and the aggregation and dispersion state of keratin fibers in a stratum corneum sample. [Figure 3] Figure 3 shows a diagram illustrating an experimental example of a barrier care system. [Figure 4] Figure 4 is an explanatory diagram of the four classes of skin barrier function, categorized by the erythema score of living skin. [Figure 5A] Figure 5A shows a typical example of the second derivative profile of methylene bending vibrations in orthorhombic intercellular lipids. [Figure 5B] Figure 5B shows a typical example of the second derivative profile of methylene bending vibrations in hexagonal intercellular lipids. [Figure 6] Figure 6 shows how the intercellular lipid packing structure changes with environmental humidity, represented by index values ​​calculated from the IR profile. [Figure 7] Figure 7 is a classification diagram of barrier properties, divided into four classes based on whether the barrier properties are high or low in low humidity environments and high or low in high humidity environments. Figure 8 shows the index values ​​of stratum corneum samples for people with high and low barrier properties in low humidity environments, and Figure 9 shows the index values ​​of stratum corneum samples for people with high and low barrier properties in high humidity environments. [Figure 8] Figure 8 shows the index values ​​of the IR profile of the intercellular lipid packing structure in stratum corneum samples under low humidity conditions, separated into individuals with high barrier function and those with low barrier function under low humidity conditions. [Figure 9] Figure 9 shows the deuterized water ratio of stratum corneum samples under high humidity conditions, separated into individuals with high and low barrier function under high humidity conditions. [Modes for carrying out the invention]

[0019] The present invention will now be described in detail with reference to the drawings.

[0020] (Overview of skin classification methods) In the skin classification method of the present invention, stratum corneum samples from predetermined areas, collected from the skin of multiple individuals, are subjected to structural analysis of intercellular lipids or keratinocytes while maintained in a low-humidity environment at a temperature of 0°C to 45°C, and also under a high-humidity environment. This temperature range of 0°C to 45°C is significant because it represents the temperature range to which skin is exposed in various aspects of human life. The low-humidity environment is defined as a humidity of 30% RH or less, preferably 10% RH to 30% RH, and the high-humidity environment is defined as 70% RH or more, preferably 70% RH to 90% RH. Within this humidity range, useful indicator values ​​for the properties of intercellular lipids or keratinocytes can be obtained by structural analysis of stratum corneum samples.

[0021] (Skin that is classified as having barrier properties) The skin that this invention classifies as a barrier includes the skin of the entire body, as well as the lips and mucous membranes. That is, skin is the tissue that covers the outer surface of the body and has a three-layer structure consisting of the epidermis (including the stratum corneum), dermis, and subcutaneous tissue. Skin includes the face such as the head, forehead, cheeks, mouth, eyes, and nose, as well as the hands and feet, scalp, ears, neck, décolleté, buttocks, chest, abdomen, delicate areas, back, elbows, cubital fossa, knees, popliteal fossa, and areas in contact with diapers and underwear. The lips have a thinner stratum corneum compared to the skin of the cheeks, etc., and lack sebaceous glands and sweat glands, but they have a layered structure of stratum corneum, epidermis, and dermis, similar to the skin of the cheeks, etc. Therefore, in this invention, the lips are classified in the same way as the skin of the cheeks, etc. Examples of mucous membranes include the conjunctiva of the eyeball, the conjunctiva of the eyelid, the nasal mucosa, and the oral mucosa.

[0022] (Indicators of barrier properties in stratum corneum samples) In stratum corneum samples stored in a low-humidity environment, indicators of barrier properties include, for example, whether the intercellular lipid packing structure is hexagonal (coarse state) or orthorhombic (orthorhombic) (dense state). Intercellular lipids are composed of components such as ceramide, free fatty acids, and cholesterol, and fill the gaps between stratum corneum cells. As shown in the experimental examples described later, when the storage environment of the stratum corneum is kept low-humidity, the packing structure of intercellular lipids becomes denser, improving barrier properties. The humidity dependence of the intercellular lipid packing structure was discovered by the inventors of this invention.

[0023] Methods for structural analysis of intercellular lipid packing structures include, for example, IR analysis such as ATR (total internal reflection measurement) and X-ray diffraction analysis.

[0024] Furthermore, in addition to the intercellular lipid packing structure, indicators of barrier properties in stratum corneum samples stored in a low-humidity environment include the content of free fatty acids and cholesterol. IR analysis also allows for the analysis of components contained in the stratum corneum under specified temperature and humidity conditions.

[0025] On the other hand, in stratum corneum samples stored in a high-humidity environment, one property that indicates barrier properties is, for example, the dispersion or aggregation of keratin fibers that make up keratinocytes. It is known that keratin fibers become dispersed when the storage environment of a stratum corneum sample is kept at high humidity. The dispersed state has higher barrier properties than the aggregated state. Whether keratin fibers are dispersed or aggregated can be analyzed by IR analysis.

[0026] In addition to the dispersion and aggregation of keratin fibers, indicators of barrier properties in stratum corneum samples stored in a high-humidity environment include the water content by weight ratio of keratinocytes, nucleation rate, cell area, ceramide content of intercellular lipids, and the composition ratio of ceramide NP to ceramide NS (NP / NS).

[0027] The water content by weight ratio and ceramide composition ratio of the stratum corneum can be analyzed by IR analysis, while the nucleation rate and cell area can be analyzed by microscopic imaging.

[0028] In particular, using the density of the intercellular lipid packing structure as an indicator of barrier properties for stratum corneum samples stored in a low-humidity environment, and using the aggregation and dispersion of keratin fibers as an indicator of barrier properties for stratum corneum samples stored in a high-humidity environment, is preferable because, as shown in Figure 2 later, the changes in barrier properties in response to increases and decreases in humidity are in opposite directions.

[0029] (Correspondence between changes in stratum corneum sample indicators and the barrier properties of living skin) To correlate the changes in indicators obtained from the structural analysis described above with the barrier properties of living skin, the barrier properties are measured in multiple individuals by the permeability of an indicator substance in the skin of living organisms kept in a low-humidity or high-humidity environment. The method for measuring the barrier properties of living skin can be the same as the method for measuring barrier properties described in Patent Document 3.

[0030] Then, based on the results of structural analysis of the intercellular lipids or keratinocyte properties of stratum corneum samples kept in a low-humidity environment, and corresponding to the measured barrier properties based on the permeability of indicator substances in living skin kept in a low-humidity environment, an axis representing the high or low barrier properties of the stratum corneum in a low-humidity environment is obtained, as shown in Figure 1. This axis representing the high or low barrier properties can also be represented, for example, as an axis representing the density or looseness of the intercellular lipid packing structure.

[0031] Similarly, a structural analysis of the intercellular lipids or keratinocyte properties of stratum corneum samples kept in a high-humidity environment is performed, and the results correspond to the measured barrier properties based on the permeability of indicator substances in living skin kept in a high-humidity environment, thereby obtaining an axis of high or low barrier properties for the stratum corneum in a high-humidity environment. This axis of high or low barrier properties can be represented, for example, as an axis representing the aggregation and dispersion of keratin fibers.

[0032] According to the barrier axis shown in Figure 1, it is possible to classify skin into at least four types: (a), (b), (c), and (d). (a) Low barrier properties in low humidity environments, and low barrier properties in high humidity environments, (b) Low barrier properties in low humidity environments, high barrier properties in high humidity environments, (c) High barrier properties in low humidity environments, High barrier properties in high humidity environments, (d) It has high barrier properties in low humidity environments and low barrier properties in high humidity environments.

[0033] These four types of classification can be rephrased as follows: (a), (b), (c), (d). (a) In low humidity environments, the intercellular lipid packing structure is coarse, while in high humidity environments, keratin fibers are aggregated. (b) In a low humidity environment, the intercellular lipid packing structure is coarse, while in a high humidity environment, keratin fibers are dispersed. (c) In a low-humidity environment, the intercellular lipid packing structure is dense, while in a high-humidity environment, keratin fibers are dispersed. (d) In low humidity environments, the intercellular lipid packing structure is dense, while in high humidity environments, keratin fibers are aggregated.

[0034] It should be noted that the classification of skin barrier types using these barrier properties is not limited to the four classifications mentioned above. For example, one could divide the axis of high and low barrier properties of the stratum corneum in low humidity environments into three categories, and the axis of high and low barrier properties of the stratum corneum in high humidity environments into two categories, resulting in a total of six classes.

[0035] Furthermore, the phenomenon that skin barrier properties can be classified into two types, for example, based on barrier properties derived from the intercellular lipid packing structure of stratum corneum samples stored in a low-humidity environment and barrier properties derived from the aggregation and dispersion of keratin fibers in stratum corneum samples stored in a high-humidity environment, can be explained as follows. That is, as shown in the erythema score in Figure 2 obtained in Experimental Example 1 described later, when the ambient temperature is 30°C, the erythema scores of the subjects vary in the ranges of ambient humidity from 10%RH to 40%RH and from 60%RH to 90%RH, indicating individual differences in skin barrier properties within this range. On the other hand, at 50%RH, the variation is small.

[0036] The lower diagram in Figure 2 schematically illustrates how the loose or dense state of the intercellular lipid packing structure and the aggregated or dispersed state of keratin fibers contained in keratinocytes change with environmental humidity. Specifically, in low-humidity environments, the intercellular lipid packing structure becomes dense due to the orthorhombic (or orthorhombic) crystal structure, which prevents water from penetrating from outside the stratum corneum. On the other hand, keratin fibers are aggregated in low-humidity environments regardless of individual differences, so their contribution to the barrier function is small. Therefore, in low-humidity environments, intercellular lipids take on the role of barrier function. This can be confirmed by experimental examples described later. Furthermore, the aggregation of keratin fibers in low-humidity environments is also described in the literature (Enamul HM et. al., Scientific Reports, 7: 15712 (2017) DOI:10.1038 / s41598-017-15921-5).

[0037] Furthermore, in high-humidity environments, when keratin fibers in keratinocytes disperse, water from outside the stratum corneum is trapped within the keratinocytes, preventing water from penetrating. On the other hand, intercellular lipids become coarser in high-humidity environments due to their hexagonal crystal structure, regardless of individual differences, and therefore contribute less to the barrier function. Consequently, in high-humidity environments, the keratin fibers within the keratinocytes take on the role of barrier function. This can also be confirmed by the experimental examples described later.

[0038] Therefore, it can be said that humidity resistance can be improved by changing the packing structure of intercellular lipids from hexagonal to orthorhombic (orthorhombic) and changing the keratin fibers from an aggregated state to a dispersed state.

[0039] In this invention, the properties of intercellular lipids or keratinocytes in a stratum corneum sample used to obtain the axis of high and low barrier properties of the stratum corneum in a low humidity environment, and the properties of intercellular lipids or keratinocytes in a stratum corneum sample used to obtain the axis of high and low barrier properties of the stratum corneum in a high humidity environment, can be determined by investigating whether the changes in various properties of the stratum corneum sample under low and high humidity conditions correspond to the barrier properties of living skin.

[0040] After obtaining the skin barrier axis shown in Figure 1, the stratum corneum collected from the subject's skin is kept in a low-humidity environment and structural analysis is performed on the axis related to the high or low barrier properties of intercellular lipids or keratinocytes. Simultaneously, structural analysis is performed on the axis related to the high or low barrier properties of keratinocytes or intercellular lipids while keeping the sample in a high-humidity environment. The analysis results are then applied to the barrier axis shown in Figure 1 to obtain the classification of the subject's skin barrier properties.

[0041] (Field of application of the present invention) According to the skin barrier classification method of the present invention, cosmetic and skincare advisors can accumulate cosmetic information such as cosmetic ingredients and product names useful for improving barrier function in environmental temperatures and humidity levels where barrier function is evaluated as low, for each type of skin barrier function, and provide subjects with the most suitable cosmetic information, skincare methods, makeup methods, haircare methods, etc., according to the subject's skin barrier function type.

[0042] For example, for skin of type (b) described above, it is recommended that subjects use a steamer before applying their usual cosmetics, or use skincare products that can be used during bathing. For skin of type (c), it is recommended that moisturizers be used in the usual way.

[0043] Furthermore, cosmetic and skincare advisors can combine the aforementioned skin barrier classification method with existing skin classification methods such as dry skin and oily skin to understand the characteristics of the skin and recommend cosmetics, skincare methods, etc., that are suitable for the subject.

[0044] Furthermore, changes in ambient temperature and humidity can be caused by external environmental factors such as season and region, as well as by actions such as wearing clothing like masks, clothes, hats, and diapers, and using saunas, baths, face washes, steamers, and steam sheets. Therefore, when advising on skincare methods, it is desirable to recommend suppressing actions that reduce the skin's barrier function and using baths and saunas that keep the skin moist, depending on the type of skin barrier function.

[0045] Furthermore, based on the skin barrier classification method of the present invention, it is possible to adapt building materials used in living spaces and travel spaces, equipment such as air conditioners, clothing materials and care methods to suit the user's barrier properties in those spaces, travel spaces (cars, trains, airplanes, etc.), or clothing.

[0046] (Barrier care system) As shown in Figure 3, the barrier care system 1 of the present invention has a database 2 in which the types of skin barrier properties classified by the skin classification method described above are associated and stored, along with cosmetic information such as active ingredients and product names of cosmetics suitable for improving the skin barrier properties of each type, makeup methods, skincare methods, and haircare methods, and a computing device 3 connected to the database 2. The computing device 3 includes a barrier type determination means and a skincare method output means. The barrier type determination means determines the type of barrier property of a subject when it receives the results of a structural analysis of predetermined properties of intercellular lipids or keratinocytes in a low-humidity or high-humidity environment of the subject's skin, and outputs the determination result to the skincare method output means. When the skincare method output means receives the type of barrier property of the subject from the skincare method output means, it uses the database 2 to select and output cosmetic information, makeup methods, skincare methods, or haircare methods corresponding to the subject's skin.

[0047] The cosmetic information stored in this database 2 includes cosmetics for the skin, cosmetics for the scalp or hair, and cosmetics for the lips, depending on the area of ​​application. It also includes cosmetics for various purposes, such as basic cosmetics like cleansers and moisturizers, UV care cosmetics, and makeup cosmetics.

[0048] The makeup methods stored in Database 2 include makeup methods to avoid and recommended methods for each type of skin barrier function. For example, for skin with a low barrier function in both low-humidity and high-humidity environments, it is recommended to use a makeup base that does not contain fragrances or alcohol, minimizes the appearance of rough texture and flaking, naturally covers dullness, and covers uneven skin tone and irregularities caused by pores and skin problems. As for makeup application methods, it is recommended to apply foundation in small amounts to the areas to be covered. It may also be recommended to apply a preparation that improves the skin barrier function before applying makeup cosmetics to the skin.

[0049] Skincare methods include massage techniques, humidification methods, and the order in which basic cosmetics are applied. Hair care methods include massage techniques, shampooing techniques, and the use of scalp cosmetics.

[0050] In Database 2, it is preferable to store information on cosmetics, makeup methods, skincare methods, and haircare methods that improve barrier function in low-humidity or high-humidity environments where the skin type is considered to have low barrier function. It is also preferable to store information on cosmetics, makeup methods, skincare methods, and haircare methods that mitigate barrier function and promote the penetration of a predetermined active ingredient in low-humidity or high-humidity environments where the skin type is considered to have high barrier function.

[0051] Therefore, this barrier care system 1 is useful when skincare advisors provide skincare advice to customers, when cosmetic manufacturers explain makeup, skincare, and haircare methods using cosmetics to cosmetic users, and when determining the direction of development for environmentally resistant skincare products that suppress the deterioration of skin barrier function in response to changes in environmental temperature and humidity. It is also useful for cosmetic users to learn about cosmetic information, skincare methods, makeup methods, and haircare methods that are suitable for improving their own skin barrier function. [Examples]

[0052] The present invention will be described in detail below based on experimental examples. Experimental Example 1 (Erythema score due to humidity changes and methyl nicotinate penetration) In the same manner as in Experimental Example 1 of Patent Document 3, the barrier function of the stratum corneum was measured using methyl nicotinate as an indicator substance on the arms of 15 healthy men and women. In this measurement, the arms were acclimatized to ambient temperature and humidity (25°C, 50%RH) for 15 minutes, and then held in a constant temperature and humidity chamber (temperature: constant at 30°C, humidity: 10, 20, 30, 40, 50, 60, 70, 80, or 90%RH) for 30 minutes. Immediately after holding in the constant temperature and humidity chamber, filter paper impregnated with methyl nicotinate was brought into contact with the arm for 15 seconds, and the erythema that developed on the arm after 20 minutes was visually observed and scored according to the criteria in Table 1 to obtain the measurement value, and a graph with the erythema score on the vertical axis was obtained as shown in Figure 2.

[0053] [Table 1]

[0054] The graph in Figure 2, which shows the erythema score, reveals that when the ambient temperature is 30°C, the subjects' erythema scores vary between 10%RH and 40%RH, and between 60%RH and 90%RH. This indicates individual differences in skin barrier function within these ranges. Furthermore, the scores are higher at both higher and lower humidity levels compared to the skin barrier function at around 50%RH, suggesting that skin barrier function is impaired at both humidity levels above and below 50%RH.

[0055] Figure 4 shows the barrier functions of the 15 individuals mentioned above, as shown in Figure 1 (i), (ii), (iii), (iv). (i) Low barrier properties in low humidity environments, and also low barrier properties in high humidity environments. (ii) Low barrier properties in low humidity environments, and high barrier properties in high humidity environments. (iii) High barrier properties in low humidity environments, and also high barrier properties in high humidity environments. (iv) High barrier properties in low humidity environments, and low barrier properties in high humidity environments. This is a classification into four classes.

[0056] In Figure 4, high barrier function in a low-humidity environment means that the erythema score is 0.5 or less at a humidity of 30% RH or less, and low barrier function in a low-humidity environment means that the erythema score is greater than 0.5 at a humidity of 30% RH or less.

[0057] Furthermore, high barrier function in a high-humidity environment refers to a situation where the erythema score is 0.5 or less at a humidity of 70% RH or higher, while low barrier function in a high-humidity environment refers to a situation where the erythema score is greater than 0.5 at a humidity of 70% RH or higher.

[0058] Experimental Example 2 (Preparation of stratum corneum samples) A hole (6 mm in diameter) was punched into an OHP sheet, and the hole was sealed with a tape having a silicone adhesive layer (Azflon Tape, manufactured by AS ONE Corporation). The adhesive layer of the tape exposed through the hole was repeatedly attached to and removed from the skin 20 times, thereby collecting stratum corneum from the entire surface of the adhesive layer exposed through the hole, and this was used as a stratum corneum sample.

[0059] Experimental Example 3 (Filling structure of intercellular lipids) The packing structure of intercellular lipids is temperature-dependent, and it is known to undergo a phase transition from orthorhombic (or orthorhombic) at low temperatures to hexagonal at high temperatures (Hatta I. et. al., Biochimica et Biophysica Acta 1758 (2006) 1830-1836). This phase transition is generally confirmed by X-ray diffraction.

[0060] On the other hand, the infrared absorption spectrum of the stratum corneum shows 1460-1475 cm⁻¹. -1 The second differential profile of methylene bending vibrations of intercellular lipids is observed (Boncheva M. et.al., Biochimica et Biophysica Acta 1778 (2008) 1344-1355).

[0061] Previous reports indicated that the IR resolution is 2 cm. -1 However, the inventors have found that the resolution of IR is 4 cm -1By setting the resolution above, it was found that the packing structure of intercellular lipids can be discriminated between orthorhombic (monoclinic) and hexagonal crystals using this second derivative profile. That is, as shown in FIGS. 5A and 5B, when the ATR-IR spectrum of the above-mentioned stratum corneum sample is measured using an FTIR device (Frontier + Universal ATR, manufactured by PerkinElmer) equipped with a single-reflection diamond ATR (incident angle 45°) unit, it can be seen that there are differences in the profiles of methylene deformation vibrations. Therefore, when measured with the above resolution, the spectrum obtained by normalizing the absorbance with the minimum value of the absorbance at 1800-1900 cm -1 and the maximum value of the absorbance at 1600-1800 cm -1 is second-differentiated. In the second derivative spectrum thus obtained, the wavenumber A is set to a specific wavenumber in the range of 1470 cm -1 ±1 cm -1 , the wavenumber B is set to a specific wavenumber in the range of 1467 cm -1 ±1 cm -1 , and the wavenumber C is set to a specific wavenumber in the range of 1472 cm -1 ±1 cm -1 . The sum of the value obtained by subtracting the second derivative coefficient at the wavenumber B from the second derivative coefficient at the wavenumber A and the value obtained by subtracting the second derivative coefficient at the wavenumber C from the second derivative coefficient at the wavenumber A can be used as an index for the packing structure of intercellular lipids. -1

[0062] Here, the resolution of IR may be higher than 4 cm -1 . The minimum value of the absorbance at 1800-1900 cm -1 means the minimum value where there is no absorption of organic substances, and the maximum value of the absorbance at 1600-1800 cm -1 means the peak value of amide I, which is the strongest protein absorption in the stratum corneum.

[0063] Also, ±1 cm -1 ​The range refers to setting the optimal reading wavenumber for the instrument within this range, depending on the spectral distortion caused by the specific characteristics of the FTIR instrument used for measurement, such as the material of the ATR crystal, the angle of incidence of light, and differences in the standard apodization function used for the Fourier transform. Therefore, for a given stratum corneum sample, the second derivative spectrum of the ATR-IR spectrum may have its maximum or minimum value at wavenumbers A, B, and C, but wavenumbers A, B, and C are not set according to the individual stratum corneum sample. Wavenumbers A, B, and C are ±1 cm due to the specific characteristics of the FTIR instrument. -1 It will be moved within the range.

[0064] More specifically, the value calculated by the following equation (1) was used as an indicator of whether the intercellular lipid packing structure was orthorhombic (orthorhombic) or hexagonal. The larger this value, the more likely the intercellular lipids are orthorhombic (orthorhombic) and the denser the packing structure. Note that the ±1 mentioned above has been omitted in the following equation (1).

[0065] Index value for intercellular lipid packing structure = {(1470cm) -1 (Second derivative of) × 2 - (1472 cm) -1 The second derivative of +1467cm² -1 (Second derivative of)} × 10,000 (1)

[0066] Stratum corneum samples were collected from the arms of 46 individuals and prepared using the method described in Experimental Example 2. The samples were then acclimatized to a constant temperature and humidity chamber at 30°C and humidity levels of 10%RH, 50%RH, or 90%RH for 10 minutes. Subsequently, the ATR-IR spectrum was measured immediately, preferably within 1 minute, and the index value was calculated from the second derivative profile using the formula described above. The results are shown in Figure 6. The reason for measuring the ATR-IR spectrum immediately after maintaining the specified temperature and humidity is that the packing structure of intercellular lipids changes rapidly with changes in ambient temperature.

[0067] Figure 6 confirms that IR analysis of stratum corneum samples reveals that the packing structure of intercellular lipids differs depending on the ambient humidity. More specifically, it can be seen that the packing structure is orthorhombic at an ambient humidity of 10% RH, and hexagonal at an ambient humidity of 90% RH. Furthermore, as the ambient humidity increases from 10% RH to 90% RH, the packing structure undergoes a phase transition from orthorhombic to hexagonal, and the index value of equation (1) decreases.

[0068] Furthermore, in the same manner as in Experimental Example 1, the arm skin of 46 individuals was kept at a temperature of 30°C and humidity of 30%RH, 50%RH, or 70%RH for 30 minutes. Using the same criteria as in Experimental Example 1, the skin was classified into those with high barrier function in low humidity environments (erythema score of 0.5 or less at humidity below 30%RH), low barrier function in low humidity environments (erythema score greater than 0.5 at humidity below 30%RH), high barrier function in high humidity environments (erythema score of 0.5 or less at humidity above 70%RH), and low barrier function in high humidity environments (erythema score greater than 0.5 at humidity above 70%RH). These results are shown in Figure 7. In addition, the results when the stratum corneum samples from Figure 6 were exposed to a temperature of 30°C and humidity of 10%RH are shown in Figure 7, divided into those with high barrier function in low humidity environments and those with low barrier function in low humidity environments, as indicated by the dashed lines. These results are shown in Figure 8.

[0069] Figure 7 suggests that individuals with low barrier function in low-humidity environments are more likely to retain a hexagonal intercellular lipid packing structure even when changing from a high-humidity to a low-humidity environment.

[0070] Experimental Example 4 (Aggregation and Dispersion State of Keratin Fibers) Stratum corneum samples from the arms of 46 individuals, prepared in the same manner as in Experimental Example 3, were treated under heavy water humidity in accordance with the description in Japanese Patent Publication No. 2016-224025, and IR spectra were obtained. However, in order to observe the changes in keratin fibers under high humidity conditions, the samples were treated under heavy water humidity of 80% RH or higher, preferably 80-90% RH, for 30-60 minutes, preferably 60 minutes, and IR spectra were obtained. The dehydration ratio calculated by the following formula (2) was used as an indicator value for the aggregation and dispersion state of keratin fibers.

[0071] Heavy water ratio = Peak intensity of amide II / Peak intensity of amide I (2)

[0072] Here, amide I and amide II are peaks derived from the amide group of keratin protein, with amide I being at 1650 cm⁻¹. -1 Nearby, Amido II is 1540 cm -1 A specific peak appears in the vicinity.

[0073] When keratin fibers aggregate due to drying, the distance between keratin fibers narrows, and more of the hydrogen atoms of the -NH groups become involved in hydrogen bonding or other intermolecular bonds (such as hydrophobic bonds), resulting in a smaller change in the amide II peak during the hydrogen-deuterium exchange reaction caused by heavy water humidity treatment. Conversely, when keratin fibers are dispersed, the hydrogen-deuterium exchange reaction occurs more easily during heavy water humidity treatment, and the change in the amide II peak decreases significantly. On the other hand, the peak value of amide I remains almost unchanged before and after heavy water humidity treatment. Therefore, the degree of dispersion of keratin fibers can be determined from the dehydration ratio, which is the peak intensity ratio of amide II / amide I after heavy water humidity treatment. Thus, the dehydration ratio can be used as an indicator of the aggregation / dispersion state of keratin fibers under high humidity conditions.

[0074] The subjects were kept at 30°C and 90% RH for 60 minutes using a potassium nitrate aqueous solution for humidity control. IR spectra were taken, and the dehydration ratio using equation (2) was calculated. These values ​​were then divided into individuals with high barrier function in a high-humidity environment and individuals with low barrier function in a high-humidity environment, as shown by the dashed line in Figure 7. The results are shown in Figure 9.

[0075] Figure 9 shows that individuals with high barrier function in high humidity environments have more dispersed keratin fibers under high humidity conditions compared to individuals with low barrier function in the same environment. Therefore, it can be seen that the heavy water ratio can be used as an indicator of high barrier function in high humidity environments.

[0076] In the above experimental examples, the ambient temperature was set to 30°C in all cases. However, it is also possible to correlate the barrier properties of living skin with the results of structural analysis of stratum corneum samples at temperatures ranging from 0 to 45°C, which is the temperature range to which skin is exposed in everyday life. [Explanation of Symbols]

[0077] 1. Barrier Care System 2 Databases 3 Computing device

Claims

1. Regarding the stratum corneum collected from the skin of multiple people, The structural analysis results of intercellular lipids or keratinocytes maintained in a low-humidity environment of 30% RH or less at a temperature of 0°C to 45°C, and the axis of high and low barrier properties of the stratum corneum in a low-humidity environment, based on the results corresponding to the measured values ​​of barrier properties based on the permeability of indicator substances in the skin of living organisms maintained in the low-humidity environment, Based on the results of structural analysis of intercellular lipids or keratinocytes maintained in a high-humidity environment of 70% RH or higher at a temperature of 0°C to 45°C, and corresponding to the measured barrier properties based on the permeability of indicator substances in the skin of living organisms maintained in the high-humidity environment, an axis for the high and low barrier properties of the stratum corneum in a high-humidity environment is obtained. Structural analysis of the stratum corneum collected from the subject's skin was performed on the axis related to the high and low barrier properties of intercellular lipids or keratinocytes while maintaining them in the low humidity environment, and structural analysis was also performed on the axis related to the high and low barrier properties of intercellular lipids or keratinocytes while maintaining them in the high humidity environment. A skin classification method that classifies the barrier properties of a subject's skin based on the axis of high or low barrier properties of the stratum corneum in a low-humidity environment and the axis of high or low barrier properties of the stratum corneum in a high-humidity environment.

2. The skin barrier properties are determined by at least four of the following types: (a), (b), (c), and (d) (a) Low barrier properties in low humidity environments, and low barrier properties in high humidity environments, (b) Low barrier properties in low humidity environments, high barrier properties in high humidity environments, (c) High barrier properties in low humidity environments, High barrier properties in high humidity environments, (d) High barrier properties in low humidity environments, low barrier properties in high humidity environments, A method for classifying skin according to claim 1, which classifies into the following categories.

3. A method for classifying skin according to claim 1, which involves analyzing the density of the intercellular lipid packing structure in a low-humidity environment and correlating the density of the intercellular lipid packing structure with the low or high barrier properties of the skin of a living organism in a low-humidity environment.

4. A method for classifying skin according to claim 1, which involves analyzing the aggregation and dispersion state of keratin fibers maintained in a high-humidity environment and correlating the aggregation and dispersion state of keratin fibers with the low or high barrier properties of biological skin maintained in a high-humidity environment.

5. By correlating the density of intercellular lipid packing structures in low-humidity environments with the low and high barrier properties of biological skin in low-humidity environments, and by correlating the aggregation and dispersion state of keratin fibers in high-humidity environments with the low and high barrier properties of biological skin in high-humidity environments, four types of skin barrier properties (a), (b), (c), and (d) can be identified. (a) In low humidity environments, the intercellular lipid packing structure is coarse, while in high humidity environments, keratin fibers are aggregated. (b) In a low humidity environment, the intercellular lipid packing structure is coarse, while in a high humidity environment, keratin fibers are dispersed. (c) In a low-humidity environment, the intercellular lipid packing structure is dense, while in a high-humidity environment, keratin fibers are dispersed. (d) In a low humidity environment, the intercellular lipid packing structure is dense, while in a high humidity environment, keratin fibers are aggregated. The method for classifying skin according to claim 2.

6. As an index of the coarseness and denseness of the filling structure of intercellular lipids, when the ATR-IR spectrum of the stratum corneum is measured with a resolution of 4 cm -1 or more, the minimum value of the absorbance at 1800-1900 cm -1 and the maximum value of the absorbance at 1600-1800 cm -1 are used to normalize the absorbance, and in the second derivative spectrum obtained by second differentiating the spectrum, the wavenumber A is set to 1470 cm -1 ±1 cm -1 in a specific wavenumber range, the wavenumber B is set to 1467 cm -1 ±1 cm -1 in a specific wavenumber range, the wavenumber C is set to 1472 cm -1 ±1 cm -1 in a specific wavenumber range, and the sum of the value obtained by subtracting the second derivative coefficient at the wavenumber B from the second derivative coefficient at the wavenumber A and the value obtained by subtracting the second derivative coefficient at the wavenumber C from the second derivative coefficient at the wavenumber A is used. The method for classifying skin according to claim 3.

7. A method for classifying skin according to claim 4, wherein the deuterium ratio is calculated using the following formula after treatment with a hydrogen-deuterium exchange reaction as an indicator of the keratin fiber aggregation and dispersion state. Heavy water conversion ratio = Peak intensity of amide II / Peak intensity of amide I

8. A skin barrier care system comprising a database in which information on cosmetics, makeup methods or skincare methods, and haircare methods suitable for improving skin barrier properties of a type, as classified by the classification method described in any one of claims 1 to 7, is associated and stored, and a computing device that uses the database to output information on cosmetics, makeup methods, skincare methods, or haircare methods associated with a skin barrier property when a skin barrier property type is input.

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