Method for evaluating hydration or swelling state of pore stratum corneum

Abstract

To provide a method for accurately evaluating a hydration or swelling state of the stratum corneum located at the boundary between keratinocytes (living cells) forming a pore and the inner cavity of the pore.SOLUTION: A method for evaluating a hydration or swelling state of a pore stratum corneum, comprises: capturing an image of the pore stratum corneum of a subject with an optical microscope; determining, based on brightness in the captured image, at least one feature related to the pore stratum corneum selected from the group consisting of brightness of swollen stratum corneum in the pore, a depth of swollen stratum corneum, a thickness of swollen stratum corneum, and brightness of keratin plug; and evaluating the hydration or swelling state of the pore stratum corneum of the subject using the feature as an index.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for evaluating the hydration or swelling state of the stratum corneum pore. [Background technology]

[0002] It is known that prolonged contact of the skin with excess moisture or occlusion of the skin leads to a decrease in the barrier function of the stratum corneum due to hydration and swelling of the skin, causing various skin problems (see Non-Patent Document 1). Skin problems associated with skin hydration and swelling are not only due to a decline in the barrier function of the stratum corneum. Sebum and sweat are secreted onto the skin through pores and sweat pores in skin appendages such as sebaceous follicles and sweat glands. If pores or sweat pores are blocked for some reason, sebum and sweat are not secreted, resulting in skin problems such as acne and miliaria. As an experimental example of secretion interference, it is known that applying a water-impermeable plastic film to the skin hydrates or swells the stratum corneum at the boundary with the pore lumen due to its blocking effect, thereby interfering with sebum secretion (see Non-Patent Document 2).

[0003] In the current coronavirus pandemic (COVID-19), many people are wearing masks for long periods of time. Wearing masks for extended periods of time has led to an increase in the number of people experiencing skin problems. The onset of acne caused by wearing masks has led to the coined term "maskne" (= mask + acne). It is speculated that one of the causes of acne caused by wearing masks is that the high humidity created by wearing a mask causes the stratum corneum in the pore cavity to swell, clogging the pores. Wearing a mask for long periods of time is known to not only cause acne, but also worsen other cosmetic problems such as rough skin and visible pores. Skin problems such as visible pores are known to be more noticeable in summer than in winter, and the increased sebum secretion in summer and the highly humid environment caused by sweating to regulate body temperature are thought to be the causes of worsening the condition. In this way, the state of hydration and swelling of the stratum corneum in the pore cavity is closely related to skin condition and skin problems.

[0004] To evaluate the hydration or swelling state of the stratum corneum on the skin surface, the water content of the stratum corneum, estimated from the electrical properties of the skin surface, is often used as an indicator. Recently, it has become possible to obtain a more detailed water depth profile inside the stratum corneum using in vivo confocal Raman microscopy, a molecular vibrational spectroscopy method (see Non-Patent Document 1). However, the electrical properties of the skin surface are the average water content for a certain area of the stratum corneum exposed to the outside air. Therefore, the water content of the stratum corneum in the microregion inside the pore, which is less exposed to the outside air, i.e., the boundary region with the pore lumen, differs from the average water content for a certain area of the stratum corneum. In vivo confocal Raman microscopy can measure water content in microregions inside the skin based on the confocal measurement principle. However, because it takes a long time to comprehensively focus on the microregion of the pore lumen, in vivo confocal Raman microscopy is currently not suitable for evaluating the hydration or swelling state of localized regions such as the pore lumen.

[0005] It has been reported that when the transmittance of peeled stratum corneum is measured with a spectrophotometer while changing the moisture content, the light transmittance decreases significantly as the moisture content increases (see Non-Patent Document 3). The decrease in light transmittance is thought to be due to the increase in light scattering caused by the hydrated or swollen stratum corneum.

[0006] As a technology for non-invasively obtaining information on the microstructure inside living skin, optical microscopes for living skin, such as reflective confocal laser scanning microscopes (e.g., Vivascope, Caliber ID, USA), are commercially available. Reflective confocal laser scanning microscopes are devices that perform tomographic imaging of backscattered light of incident near-infrared laser light from a living organism, enabling non-invasive observation of the microstructure of the epidermis and upper dermis with cellular resolution. Reflective confocal laser scanning microscopes have been used to capture images of pore diameter, the boundary between the keratinocytes (living cells) that make up the pores and the pore lumen, and the microscopic morphology of the contents (keratinocyte plugs) within the pore lumen, and have revealed various states of pore morphology by comparing images between healthy subjects and acne patients (see Non-Patent Document 4). However, there have been no reports to date of direct observation of the hydration or swelling state of the stratum corneum. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Contact Dermatitis., 2019, vol. 80, p. 228-233 [Non-patent document 2] British Journal of Dermatology, 1976, vol. 94, p. 431-434 [Non-patent document 3] J. Soc. Cosmet. Chem. Japan, 2001, Vol. 35, No. 4, p. 333-337 [Non-patent document 4] JEADV, 2015, vol. 29, p. 933-939 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for accurately evaluating the hydration or swelling state of the stratum corneum present at the boundary between the keratinocytes (living cells) that constitute pores and the pore lumen. [Means for solving the problem]

[0009] In view of the above problems, the present inventors have conducted extensive research. Specifically, they compared images of the same pore on a human cheek taken with a reflective confocal laser microscope before and after changing the moisture content of the cheek. They found that in the stratum corneum, located at the boundary between the keratinocytes (living cells) that make up the pore and the pore lumen, the image brightness, which corresponds to the backscattering intensity, increased with increasing moisture content. They also found that this image brightness visualizes the hydration or swelling state of the pore stratum corneum. The present invention has been completed based on these findings.

[0010] The present invention relates to a method for evaluating the hydration or swelling state of the stratum corneum of a subject, which comprises imaging the stratum corneum of a subject using an optical microscope, determining at least one characteristic quantity related to the stratum corneum of a subject based on the brightness of the image, the characteristic quantity being selected from the group consisting of brightness of the swollen stratum corneum in the pore, depth of the stratum corneum, thickness of the stratum corneum, and brightness of a keratinocyte plug, and evaluating the hydration or swelling state of the stratum corneum of a subject using the characteristic quantity as an index. [Effects of the Invention]

[0011] According to the present invention, the hydration or swelling state of the pore stratum corneum, which has previously been difficult to evaluate, can be accurately evaluated by using a characteristic quantity determined from the brightness of an image captured by an optical microscope of the stratum corneum located at the boundary between the keratinocytes (living cells) that make up the pore and the pore lumen as an indicator. [Brief explanation of the drawings]

[0012] [Figure 1] Figure 1(A) is a photograph (substitute for a drawing) showing a horizontal cross-sectional image of the area just below the stratum corneum of a pore before hydration and swelling treatment, taken using a reflective confocal laser scanning microscope. Figure 1(B) is a photograph (substitute for a drawing) showing a horizontal cross-sectional image of the area just below the stratum corneum of a pore (at the depth of the granular cell layer) immediately after hydration and swelling treatment, taken using a reflective confocal laser scanning microscope. [Figure 2] Figure 2(A) is a photograph (substitute for a drawing) showing a horizontal cross-section image taken using a reflective confocal laser scanning microscope at a depth of 15 μm from the granular cell layer before hydration and swelling treatment. Figure 2(B) is a photograph (substitute for a drawing) showing a horizontal cross-section image taken using a reflective confocal laser scanning microscope at a depth of 15 μm from the granular cell layer immediately after hydration and swelling treatment. [Figure 3] Figure 3(A) is a photograph, taken using a reflective confocal laser microscope, showing a horizontal cross-sectional image of the area just below the stratum corneum of a pore before occlusion treatment, and Figure 3(B) is a photograph, taken using a reflective confocal laser microscope, showing a horizontal cross-sectional image of the area just below the stratum corneum of a pore immediately after occlusion treatment. [Figure 4]Figure 4(A) is a photograph (substitute for a drawing) showing a horizontal cross-sectional image taken using a reflective confocal laser microscope at a depth of 15 μm from the granular cell layer before occlusion treatment, and Figure 4(B) is a photograph (substitute for a drawing) showing a horizontal cross-sectional image taken using a reflective confocal laser microscope at a depth of 15 μm from the granular cell layer immediately after occlusion treatment. [Figure 5] FIG. 1 is a diagram showing a schematic diagram of changes in the stratum corneum caused by hydration or swelling. [Figure 6] FIG. 1 is a diagram schematically showing information on a captured image that can be preferably used as an evaluation criterion in the present invention. [Figure 7] FIG. 1 is a diagram schematically showing one embodiment of a method for normalizing the brightness of a swollen stratum corneum. [Figure 8] 1 is a graph showing the results of normalizing the brightness obtained from images of the stratum corneum pores under various environments taken using a reflective confocal laser microscope. DETAILED DESCRIPTION OF THE INVENTION

[0013] In the method of the present invention for evaluating the hydration or swelling state of the stratum corneum of a subject, the hydration or swelling state of the stratum corneum of a subject is evaluated using a characteristic quantity related to the stratum corneum determined from an image captured by an optical microscope as an index. The present inventors have used a reflective confocal laser microscope to image the pore stratum corneum of human skin, and have studied how the imaged pore stratum corneum portion changes with changes in the moisture content of the skin.As mentioned above, it is known that the light scattering property of the stratum corneum portion increases with an increase in the moisture content of the stratum corneum.Based on this knowledge, the inventors have conducted detailed studies and, as shown in the examples below, have found that, in images captured using a reflective confocal laser microscope, the feature quantity determined from the image brightness can be used as an index to clearly identify the hydrated and swollen stratum corneum portion and easily distinguish it from other portions. The present invention will be described in detail below.

[0014] Normally, epidermal cells keratinize from the depths of the skin toward the surface. Pores are tubular and open from the depths of the skin toward the surface. The keratinocytes (living cells) that make up the pores keratinize toward the pore lumen in a manner similar to that of normal epidermis, forming a stratum corneum at the boundary between the keratinocytes (living cells) and the pore lumen. To distinguish this stratum corneum from the stratum corneum formed by normal epidermis, it is defined herein as the "pore stratum corneum." As used herein, "hydration" of a pore means an increase in the amount of water in the pore tissue due to a water load, a occlusive environment, or the like. As used herein, "swelling" of pores refers to structural changes that accompany an increase in moisture in the pore tissue, including microscopic structural changes in the keratin proteins that make up the pore, as well as the resulting deformation of the stratum corneum cell morphology and increase in thickness.

[0015] The optical microscope used in the present invention is not particularly limited as long as it can irradiate the skin with light, form an image of the backscattered light from the skin using a lens, and observe it, and can non-invasively capture horizontal tomographic images of the skin to a depth of about 150 μm from the skin surface. The optical microscope used in the present invention includes a confocal laser microscope. Imaging of the stratum corneum using a confocal laser microscope can be performed according to a conventional method, for example, by referring to JEADV, 2015, vol. 29, pp. 933-939. Alternatively, an optical microscope utilizing optical coherence tomography can also be used. In the present invention, from the viewpoint of non-invasively obtaining information on the microstructure inside the skin, it is preferable to use a confocal laser microscope, and more preferably, a reflective confocal laser microscope.

[0016] In the present invention, the pore stratum corneum of a subject is imaged using an optical microscope.The method for evaluating the hydration or swelling state of the pore stratum corneum of the present invention can be applied to the pores of the whole body of a human.Therefore, there is no particular limitation on the part for imaging the pore stratum corneum, and any part of the whole body, such as the head, face, neck, chest, abdomen, back, waist, buttocks, upper limbs, or lower limbs, can be selected to image the pore stratum corneum.The part for imaging the pore stratum corneum is preferably the head, face, chest, or back, where many seborrheic hair follicles are distributed, and the cheek is more preferred, as it is easy to cause pore troubles such as acne. The pore and stratum corneum images are captured by gradually changing the imaging depth from the skin surface toward the interior of the skin to capture horizontal cross-sectional images. Specifically, horizontal cross-sectional images are captured every 1 to 12 μm, preferably every 3 to 5 μm, from the skin surface to a depth of 150 μm, preferably 60 μm.

[0017] As shown in the examples below, the optical properties of the stratum corneum change with the change in the hydration or swelling state of the stratum corneum, and the image brightness of the part of the captured image where the stratum corneum is present changes, and a white ring-shaped structure corresponding to the hydrated or swollen stratum corneum appears around the pore, and the brightness of the keratinocyte plug, which is the content of the pore, increases. Utilizing this phenomenon, in the present invention, a feature value that reflects the hydration or swelling state of the stratum corneum is determined from the information on the image brightness of the part of the captured image where the stratum corneum is present, and the determined feature value is used as an index to evaluate the hydration or swelling state of the stratum corneum.

[0018] In the present invention, the evaluation of the hydration or swelling state of the pore stratum corneum uses at least one feature selected from the group consisting of "brightness of the swollen stratum corneum," "depth of the swollen stratum corneum," "thickness of the swollen stratum corneum," and "brightness of the keratinocyte plug" in the pore. These feature values can be determined from the image brightness, which indicates the brightness of an image of the pore stratum corneum captured by an optical microscope. Each feature value will be explained below.

[0019] "Brightness of swollen stratum corneum" refers to the brightness of hydrated and swollen stratum corneum as indicated by image brightness. Here, "swollen stratum corneum" refers to the region of the pore stratum corneum where light scattering increases due to hydration or swelling, resulting in brightness above a certain level, specifically the white ring-shaped region observed around the pore in the pore stratum corneum due to hydration or swelling. The brightness of the swollen horny layer can be judged by visual observation, but it is preferable to use image analysis software to analyze the brightness of the captured image to judge.For example, in the horizontal cross-sectional image of the pore horny layer, a suitable brightness threshold can be set to define the boundary of the white ring-shaped area around the pore, and the area of the swollen horny layer can be determined, and the average brightness of this swollen horny layer can be taken as the brightness of the swollen horny layer.Alternatively, the area of the pore horny layer where the swollen horny layer is expected to appear can be preliminarily determined as the swollen horny layer area, and the average brightness of this imaginary swollen horny layer area can be taken as the brightness of the swollen horny layer. The hypothetical swollen stratum corneum region can be set within a certain distance from the pore lumen wall. Here, the certain distance is 5 to 50 μm, preferably 10 to 40 μm. The hypothetical swollen stratum corneum region may be the same in horizontal cross-sectional images captured at different depths, or different regions may be set for each depth. As shown in the examples below, when the pore stratum corneum is hydrated or swollen by a hydration treatment or a blocking treatment, the hydrated or swollen stratum corneum region is observed as a white ring centered on the pore. In a horizontal cross-sectional image of the subject's pore stratum corneum, the hydration or swelling state of the pore stratum corneum, indicated by the appearance of a white ring-shaped region around the pore, can be evaluated using the "brightness of the swollen stratum corneum" as a characteristic quantity.

[0020] "Swelling stratum corneum depth" refers to the maximum depth at which a swollen stratum corneum is observed. In horizontal cross-sectional images captured at stepwise varying depths, the maximum depth at which a swollen stratum corneum is observed can be determined as the swelling stratum corneum depth. The presence or absence of a swollen stratum corneum in a horizontal cross-sectional image may be determined visually, but it is preferable to set a certain threshold for the average brightness of the hypothetical swollen stratum corneum region described above and determine whether or not the threshold is exceeded. As will be shown in the Examples below, in pores with a more advanced hydration or swelling state, a white ring-shaped region around the pore is observed even in horizontal cross-sectional images at a deeper position. In a horizontal cross-sectional image of the pore stratum corneum of a subject, the hydration or swelling state of the pore stratum corneum, indicated by the depth from the skin surface at which a white ring-shaped region around the pore is observed, can be evaluated using the "swelled stratum corneum depth" as a feature.

[0021] "Swelling stratum corneum thickness" refers to the width of the swollen stratum corneum observed as a white ring around a pore in a captured horizontal cross-sectional image. Specifically, the area of the swollen stratum corneum is determined in the horizontal cross-sectional image as described above, and the average width of the determined ring-shaped swollen stratum corneum can be taken as the swelling stratum corneum thickness. As will be shown in the Examples below, in pores where hydration or swelling of the pore stratum corneum is more advanced, a wider white ring-shaped region is observed around the pore. In a horizontal cross-sectional image of the pore stratum corneum of the subject, the hydration or swelling state of the pore stratum corneum, which is indicated by the width of the white ring-shaped region present around the pore, can be evaluated using the "swollen stratum corneum thickness" as a feature.

[0022] "Brightness of keratinous plugs" refers to the brightness of keratinous plugs observed in pores. Specifically, it can be determined as the average brightness of keratinous plugs observed in pores in the captured horizontal cross-sectional image. As will be shown in the Examples below, the brightness of the keratinized plugs in the pores becomes brighter as the pore stratum corneum hydrates or swells. In a horizontal cross-sectional image of the subject's pore stratum corneum, the hydration or swelling state of the pore stratum corneum is indicated by the brightness of the keratinized plugs in the pores, and the hydration or swelling state of the pore stratum corneum can be evaluated using the "brightness of the keratinized plugs" as a feature.

[0023] The horizontal cross-sectional image of the stratum corneum used in the present invention may have unstable image brightness depending on the imaging conditions, such as the light source of the optical microscope used, and the optical properties of the skin, which vary from subject to subject. Therefore, in order to stably evaluate the hydration or swelling state of the stratum corneum regardless of the imaging conditions, it is preferable to normalize the image brightness of the area where the stratum corneum is present with the image brightness of the area where the stratum corneum is not present. An example will be described in which the "brightness of the swollen stratum corneum" is evaluated by setting a virtual swollen stratum corneum region.

[0024] As shown in the Examples below, a closed curve is drawn along the pore lumen wall at the transition point from the pore lumen to the surrounding pore stratum corneum in a horizontal cross-sectional image of the pore stratum corneum, and then another closed curve is drawn 30 μm outward from the first curve. The region between the two curves is designated as region of interest A (ROIA), and ROIA is set as the hypothetical swollen stratum corneum region, and its average brightness (average brightness A) is calculated. Furthermore, another closed curve is drawn 30 μm outward from the second curve, and the region between the second and third curves is designated as region of interest B (ROIB), and its average brightness (average brightness B) is calculated. When evaluating the hydration or swelling state of the stratum corneum using the "brightness of the swollen stratum corneum" as a feature, the average brightness A of the hypothetical swollen stratum corneum region is replaced with a normalized value, that is, the average brightness A divided by the average brightness B of the region where the stratum corneum is not present, (average brightness A / average brightness B), and this value is used to evaluate the hydration or swelling state of the stratum corneum. By normalizing the "brightness of the stratum corneum" as a value, a stable feature value can be obtained regardless of the image capturing conditions or the optical properties of the skin. Similarly, for the feature quantities of "depth of swollen stratum corneum" and "brightness of keratinocyte plugs," stable feature quantity values can be obtained by normalizing them using the image brightness of areas where no pore stratum corneum is present.

[0025] In the present invention, the hydration or swelling state of the stratum corneum of a subject is evaluated using at least one characteristic quantity related to the stratum corneum of the pore selected from the group consisting of "brightness of the stratum corneum," "depth of the stratum corneum," "thickness of the stratum corneum," and "brightness of the keratinocyte plug" as an index. For the evaluation, it is preferable to associate these characteristic quantities with the hydration or swelling state of the stratum corneum of the pore in advance. Below, the relationship between the characteristic quantities related to the stratum corneum obtained from images captured by an optical microscope and the hydration or swelling state of the stratum corneum of the pore will be specifically explained. However, the present invention is not limited thereto.

[0026] First, a site for evaluating the hydration or swelling state of the pore stratum corneum is determined, and an image of the determined site is taken with an optical microscope. Then, a given article is applied or worn on the determined area for a certain period of time. If moisture is actively added to the given article, for example, by using water-soaked cotton wool, the stratum corneum can be hydrated or swollen. Herein, a treatment that actively adds moisture to the stratum corneum is also referred to as a "hydration / swelling treatment." In contrast, a hydrated or swollen environment can also be achieved on the skin by inhibiting water evaporation from the skin to the external environment. Herein, a treatment that inhibits water evaporation from the skin to the external environment by applying a moisture-free article to the skin is also referred to as an "occlusive treatment." After such treatment is performed for a certain period of time, an image of the area to be evaluated is taken using an optical microscope.

[0027] Images taken before and after the "hydration / swelling treatment" or before and after the "occlusion treatment" were compared to correlate how the image brightness of the area where the pore stratum corneum is present changes due to the "hydration / swelling treatment" or "occlusion treatment" and how the feature quantities determined based on the image brightness change. Adding moisture increases the image brightness of the area where the pore stratum corneum is present, increasing the feature quantities "brightness of the swollen stratum corneum" and "brightness of the keratinocyte," and increasing the feature quantities "depth of the swollen stratum corneum" and "thickness of the swollen stratum corneum." Furthermore, although not as severe as when moisture is added, creating an environment that prevents water evaporation from the skin to the external environment also increases the image brightness of the area where the pore stratum corneum is present, and the various feature quantities change in a similar manner. Information on such changes in various features is associated with the hydration or swelling state of the pore stratum corneum and used as a criterion for evaluating the hydration or swelling state of the pore.

[0028] Then, an optical microscope is used to image the stratum corneum of the subject whose stratum corneum hydration or swelling state is to be evaluated. The stratum corneum hydration or swelling state of the subject's stratum corneum is evaluated based on various feature quantities determined from the brightness of the image, in accordance with the aforementioned criteria. Absorbent articles such as absorbent cotton, sanitary napkins, disposable diapers, cloth diapers, training pants, adult diapers, sweat pads, urine absorption pads, postpartum pads, panty liners, and absorbent pads absorb urine and menstrual blood and are used in contact with the skin. Therefore, when evaluating the hydration or swelling state of the stratum corneum after wearing an absorbent article for a certain period of time, the correlation between the changes in various characteristic quantities and the hydration or swelling state of the stratum corneum when a "hydration / swelling treatment" is performed, which actively adds water to the skin stratum corneum, is used as a criterion. On the other hand, wound protection materials such as masks, rubber gloves, adhesive plasters, gauze, and bandages, and steam heating devices, unlike absorbent articles, do not actively add moisture to the stratum corneum, but instead create a hydrated or swollen environment for the stratum corneum by preventing water evaporation from the skin to the external environment. Therefore, when evaluating the hydration or swelling state of the stratum corneum after wearing these articles for a certain period of time, the correlation between the changes in various characteristic quantities and the hydration or swelling state of the stratum corneum when an "occlusion treatment" is performed to prevent water evaporation from the skin to the external environment is used as a criterion.

[0029] The relationship between various characteristic quantities used as criteria for evaluating the hydration or swelling state of pores and the hydration or swelling state of the stratum corneum pores will be specifically described below.

[0030] As the moisture content of the stratum corneum increases, the light scattering property of the stratum corneum increases. Therefore, in optical microscope photographs, the areas where the hydrated or swollen stratum corneum is present have higher image brightness than other areas. As such, there is a correlation between the hydration or swelling state of the stratum corneum and the brightness of the captured image of the stratum corneum, so the hydration or swelling state of the stratum corneum can be evaluated using the feature amount determined based on the image brightness of the area where the stratum corneum is present in the captured image as an index. Various feature quantities determined based on the brightness of the captured image can be determined using image analysis software. Since various feature quantities based on image brightness can be easily determined by standard methods, the hydration or swelling state of the pore stratum corneum can be evaluated simply and quickly based on such correlations.

[0031] According to the present invention, the above-mentioned change in image brightness accompanying the hydration or swelling of the pore stratum corneum can be captured not only on the skin surface but also in a region from the skin surface to a predetermined depth. Therefore, by obtaining information on the image brightness of the location of the pore stratum corneum at each depth from images of the subject's pore stratum corneum taken at regular depths from the skin surface using an optical microscope, and evaluating the hydration or swelling state of the pore stratum corneum from the obtained information, it is possible to capture in detail the changes in the hydration or swelling state from the skin surface to the interior of the skin.

[0032] In the present invention, the hydration or swelling state is evaluated using various characteristic quantities related to the pore and stratum corneum. For example, a reference value may be set for each feature, and when the feature reaches the reference value, the pore stratum corneum of the evaluation target may be evaluated as being in a hydrated or swollen state. There are no particular limitations on the method for setting the reference value, and the brightness of the pore stratum corneum in the image captured after performing the ``hydration / swelling treatment'' or ``occlusion treatment'' for a certain period of time, the depth of the swollen stratum corneum where the brightness has increased, the thickness of the pore stratum corneum, and the brightness of the keratinocyte plug can be set as the reference value.

[0033] The present invention can provide an evaluation device for evaluating the hydration or swelling state of the stratum corneum, which is suitable for use in a method for evaluating the hydration or swelling state of the stratum corneum of a pore, and which causes a computer to function to evaluate the hydration or swelling state of the stratum corneum of a subject and output the results. The device for evaluating the hydration or swelling state of the stratum corneum of the present invention stores information regarding the correlation between at least one characteristic quantity related to the stratum corneum, selected from the group consisting of brightness of the swelled stratum corneum in the pore, depth of the stratum corneum, thickness of the stratum corneum, and brightness of the keratinocyte plug, which is determined based on the brightness of the stratum corneum obtained from an image captured by an optical microscope, and the hydration or swelling state of the stratum corneum, and is equipped with a calculation means for evaluating the hydration or swelling state of the stratum corneum of the subject based on the information regarding the correlation, using the characteristic quantity as an index. The calculation means is realized by, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit) executing a program stored in the device for evaluating the hydration or swelling state of a pore-stratum corneum of the present invention. In addition, part or all of the calculation means may be realized by hardware such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array), or may be realized by a combination of software and hardware.

[0034] Similar to the device for evaluating the hydration or swelling state of the stratum corneum, the present invention can also provide a system for evaluating the hydration or swelling state of the stratum corneum, which is suitable for use in a method for evaluating the hydration or swelling state of the stratum corneum, and which evaluates the hydration or swelling state of the stratum corneum of a subject and causes a computer to function to output the results. The system for evaluating the hydration or swelling state of a stratum corneum of the present invention has a server that communicates via a network. This server is equipped with a calculation means, similar to the device for evaluating the hydration or swelling state of a stratum corneum of the present invention. The calculation means provided in the system for evaluating the hydration or swelling state of a stratum corneum of the present invention can have the same configuration as the calculation means provided in the aforementioned evaluation device. The calculation means is realized, for example, by executing a program stored in a server. Furthermore, part or all of the calculation means may be realized by hardware, or may be realized by a combination of software and hardware.

[0035] The method of the present invention for evaluating the hydration or swelling state of the stratum corneum pores can be used to evaluate the performance of products such as masks or rubber gloves, absorbent articles (absorbent cotton, sanitary napkins, paper diapers, cloth diapers, training pants, adult diapers, sweat pads, urine pads, postpartum pads, panty liners, absorbent pads, etc.), wound protection materials (adhesive plasters, gauze, bandages, etc.), and steam heating devices. For example, by using the method of the present invention for evaluating the hydration or swelling state of the stratum corneum of a pore, the hydration or swelling state of the stratum corneum after wearing the article for a certain period of time can be used to safely, easily, and quickly evaluate the performance of the article (e.g., moisture (wetness) absorbency, moisture vapor (stuffiness) dissipation to the outside (breathability), presence or absence of skin contact, contact pressure on the skin, susceptibility to skin troubles). When evaluating absorbent articles, absorbent articles soaked in saline or simulated urine may also be used for evaluation. The effect of the article on pores is also correlated with local transepidermal water loss and sweat rate. Therefore, it is believed that there are significant differences in the hydration or swelling state within the article depending on the region. According to the present invention, the hydration or swelling state of individual stratum corneums can be evaluated at various regions within the article, allowing the regional differences in the effect of the internal environment of the article on the stratum corneum to be understood. By evaluating the hydration or swelling state of the pore stratum corneum after wearing or application of an article according to the present invention, it is possible to estimate the hydration or swelling state of the pore stratum corneum before and after wearing when comparing current products with improved products, even for masks, rubber gloves, absorbent articles, wound protection materials, and steam warmers. When the skin stratum corneum becomes hydrated or swollen, not only does its barrier function decrease, but sebum accumulates in the pores, causing pore blockage and skin troubles. Therefore, by evaluating the hydration or swelling state of the pore stratum corneum after wearing or application of an article according to the present invention, the performance of the article can be evaluated safely and simply in a short time, and the development of masks and the like can be efficiently carried out.

[0036] In relation to the above-mentioned embodiments, the present invention further discloses the following methods for evaluating the hydration or swelling state of the stratum corneum, methods for evaluating the performance of an article, and devices or systems for evaluating the hydration or swelling state of the stratum corneum.

[0037] <1> A method for evaluating the hydration or swelling state of a pore stratum corneum, comprising: The subject's pore stratum corneum was photographed using an optical microscope. determining at least one feature value related to the pore stratum corneum selected from the group consisting of brightness of the swollen stratum corneum in the pore, depth of the swollen stratum corneum, thickness of the swollen stratum corneum, and brightness of the keratinocyte plug based on the brightness of the captured image; Evaluating the hydration or swelling state of the pore stratum corneum of the subject using the feature amount as an index. A method for evaluating the hydration or swelling state of the stratum corneum.

[0038] <2> The optical microscope is a confocal laser microscope. <1> The method described in paragraph . <3> determining a feature value that reflects the hydration or swelling state of the stratum corneum from information on the image brightness of a portion of the captured image where the stratum corneum is present, and evaluating the hydration or swelling state of the stratum corneum using the feature value as an index; <1> or <2> The method described in paragraph . <4> The image brightness of the area where the pore stratum corneum is present is normalized by the image brightness of the area where the pore stratum corneum is not present. <3> The method described in paragraph . <5> Evaluate the hydration or swelling state of the pore stratum corneum of the subject's cheek. <1> ~ <4> 10. The method according to any one of claims 1 to 9. <6> The subject's pore stratum corneum to which moisture has been actively added is imaged using an optical microscope, and the images taken before and after the active addition of moisture are compared to correlate how the image brightness at the location where the pore stratum corneum is present changes with how the feature amount determined based on the image brightness changes due to the active addition of moisture. <1> ~ <5> 10. The method according to any one of claims 1 to 9. <7> Using an optical microscope, the stratum corneum of the subject whose evaporation of water from the skin to the external environment has been hindered is imaged, and the images taken before and after the hindering of evaporation of water are compared to correlate how the brightness of the image at the location where the stratum corneum is present changes due to the hindering of evaporation of water and how the feature amount determined based on the brightness of the image changes. <1> ~ <6> 10. The method according to any one of claims 1 to 9. <8> In a horizontal cross-sectional image of the subject's pore stratum corneum, the appearance of a white ring-shaped area around the pore is confirmed, and the brightness feature of the swollen stratum corneum is determined, thereby evaluating the hydration or swelling state of the pore stratum corneum. <1> ~ <7> 10. The method according to any one of claims 1 to 9. <9> In a horizontal cross-sectional image of the subject's pore stratum corneum, the depth from the skin surface at which a white ring-shaped area around the pore is observed is measured to determine the feature value of the swelling stratum corneum depth, thereby evaluating the hydration or swelling state of the pore stratum corneum. <1> ~ <8> 10. The method according to any one of claims 1 to 9. <10> In a horizontal cross-sectional image of the subject's pore stratum corneum, the width of a white ring-shaped area present around the pore is measured to determine a characteristic value of the swollen stratum corneum thickness, thereby evaluating the hydration or swelling state of the pore stratum corneum. <1> ~ <9> 10. The method according to any one of claims 1 to 9. <11> In a horizontal cross-sectional image of the subject's pore stratum corneum, the brightness of the keratinized plug in the pore is measured to determine the feature value of the brightness of the keratinized plug, thereby evaluating the hydration or swelling state of the pore stratum corneum. <1> ~ <10> 10. The method according to any one of claims 1 to 9. <12> Using an optical microscope, images of the subject's pore stratum corneum were taken at regular depths from the skin surface. From the captured image, information on the image brightness of the area where the pore stratum corneum is present is obtained for each depth, Based on the obtained information, the hydration or swelling state of the pore stratum corneum extending from the skin surface to the inside of the skin is evaluated. <1> ~ <11> 10. The method according to any one of claims 1 to 9. <13> For the pore stratum corneum in a hydrated or swollen state, reference values are set for the brightness of the pore stratum corneum in the captured image, the depth of the swollen stratum corneum where the brightness has increased, the thickness of the pore stratum corneum, and the brightness of the keratinocyte plug, In an image of the pore stratum corneum of the subject, when at least one feature selected from the group consisting of the brightness of the pore stratum corneum, the depth of the swollen stratum corneum with increased brightness, the thickness of the pore stratum corneum, and the brightness of the keratinocyte plug reaches the reference value, the pore stratum corneum of the subject is evaluated to be in a hydrated or swollen state. The aforementioned <1> ~ <12> 10. The method according to any one of claims 1 to 9.

[0039] <14> The subject wears one item selected from the group consisting of a mask, rubber gloves, absorbent articles, steam heating devices, and wound protection materials, and <1> ~ <13> A method for evaluating the performance of an article, which comprises evaluating the hydration or swelling state of the stratum corneum using the method described in any one of the above, and evaluating the effect of wearing the article on the stratum corneum. <15> The aforementioned <1> ~ <13> An apparatus for evaluating the hydration or swelling state of a pore-like stratum corneum, used in any one of the methods described above, The device stores information relating to the correlation between at least one feature quantity of the stratum corneum selected from the group consisting of brightness of the swelled stratum corneum in the pore, depth of the stratum corneum, thickness of the stratum corneum, and brightness of the keratinocyte plug, which is determined based on the brightness of the stratum corneum obtained from an image captured by an optical microscope, and the hydration or swelling state of the stratum corneum, and is equipped with a calculation means for evaluating the hydration or swelling state of the stratum corneum of the subject using the feature quantity as an index based on the information relating to the correlation. A device for evaluating the hydration or swelling state of the stratum corneum. <16> The aforementioned <1> ~ <13> A system for evaluating the hydration or swelling state of the stratum corneum, used in any one of the methods described above, A server that communicates via a network is included, The server stores information on the correlation between at least one feature quantity of the stratum corneum selected from the group consisting of brightness of the swelled stratum corneum in the pore, depth of the stratum corneum, thickness of the stratum corneum, and brightness of the keratinocyte plug, which is determined based on the brightness of the stratum corneum obtained from an image captured by an optical microscope, and the hydration or swelling state of the stratum corneum, and is equipped with a calculation means for evaluating the hydration or swelling state of the stratum corneum of the subject based on the information on the correlation and using the feature quantity as an index. A system for assessing the hydration or swelling state of the stratum corneum. [Example]

[0040] The present invention will be described in more detail below with reference to examples, but is not limited thereto. Changes in the stratum corneum pores under experimental hydration or swelling conditions were evaluated using pore images taken with a reflective confocal laser microscope (trade name: Vivascope, manufactured by Caliber ID, USA).

[0041] (Test Example 1) The stratum corneum hydration and swelling treatment was performed based on an existing report (Non-Patent Document 1). A cut cotton ball (4 x 4 cm) soaked in 1280 μL of distilled water was fixed with medical tape to the center of the cheek of a male in his 50s, and the male was allowed to rest in a seated position in a normal office environment for 3 hours. This treatment was observed to approximately double the thickness of the stratum corneum on the surface of human skin, and to significantly change the microstructure of the stratum corneum in pigskin, confirming that the stratum corneum of the epidermis was hydrated and swelled.

[0042] The same pore was imaged using a reflectance confocal laser scanning microscope before and immediately after hydration and swelling treatment. The laser power of the light source was set to 1.5 mW, and horizontal tomographic images of the pore were acquired at depths of 3 μm up to 60 μm. Horizontal cross-sectional images of the pore just below the stratum corneum (at the granular cell layer) are shown in Figure 1(A) (before hydration and swelling treatment) and Figure 1(B) (immediately after hydration and swelling treatment), while horizontal cross-sectional images of the tomographic image 15 μm deeper below the granular cell layer are shown in Figure 2(A) (before hydration and swelling treatment) and Figure 2(B) (immediately after hydration and swelling treatment). As shown in Figures 1 and 2, the hydration and swelling treatment increased the brightness of the stratum corneum at the boundary between the keratinocytes (living cells) that make up the pore and the pore lumen. This result indicates that the hydration and swelling treatment increased the light scattering intensity. This brightness change was confirmed to extend at least 15 μm deeper than the granular cell layer. Furthermore, before treatment, a portion of the stratum corneum at the boundary with the pore lumen was observed as a high-brightness area, but after treatment, this high-brightness area became thicker and surrounded the entire lumen. Furthermore, the lumen is thought to contain the contents inside the pore (keratin plugs), and the brightness of these plugs also increased. Among these changes, the increase in brightness and thickness of the stratum corneum at the boundary with the swollen pore lumen was particularly significant, resulting in a difference in brightness compared to the contents inside the pore (keratin plugs) and the surrounding keratinocytes (living epidermal cells), and was observed as a characteristic ring-shaped structure.

[0043] The amount of sebum was measured using a commercially available sebum meter (trade name: sebumeter, manufactured by C+K) 10 and 47 minutes after the hydration and swelling treatment. The results showed that the amount of sebum was reduced by approximately 30% (after 10 minutes) and 60% (after 60 minutes) compared to when the hydration and swelling treatment was not performed. These results confirmed that the hydration and swelling treatment suppressed sebum secretion. This phenomenon is thought to be due to the fact that the hydration and swelling treatment increases the thickness of the stratum corneum in the pore cavity, resulting in the inhibition of sebum secretion to the skin surface.

[0044] (Test Example 2) Next, changes in the stratum corneum under experimental occlusion conditions were evaluated using pore images captured using a reflective confocal laser scanning microscope. It is known that water is constantly evaporating from the body into the external environment, and that a hydrated or swollen environment on the skin can be achieved simply by preventing water from evaporating from the skin into the external environment, without the need to supply water from the outside as in Test Example 1.

[0045] A waterproof membrane (Saran Wrap, manufactured by Asahi Kasei) was cut into a 4x4cm piece and attached to the center of a man's cheek in his 50s. The subject was then allowed to rest in a seated position for 3 hours in a variable-temperature room (room temperature 21.8°C, relative humidity 50%). A medical dressing (Tegaderm, manufactured by 3M) was used to secure the waterproof membrane. The same pores were imaged using a reflective confocal laser microscope before and immediately after the occlusion treatment. Images taken before the occlusion treatment were taken after washing the face and allowing the pores to acclimate for 20 minutes or more in a temperature-controlled room (temperature 21.8°C, relative humidity 50%). The imaging conditions for the reflective confocal laser microscope were set to the same conditions as in Test Example 1. Horizontal cross-sectional images of the area just below the stratum corneum (at the depth of the granular cell layer) are shown in Figure 3(A) (before occlusion treatment) and Figure 3(B) (immediately after occlusion treatment), and horizontal cross-sectional images of a tomographic image at a location 15 μm deeper than the granular cell layer are shown in Figure 4(A) (before occlusion treatment) and Figure 4(B) (immediately after occlusion treatment). As shown in Figure 3, after occlusion treatment, a bright ring was clearly observed just below the stratum corneum (at the depth of the granular cell layer) (Figure 3(B)). Furthermore, while a portion of the stratum corneum at the boundary with the pore lumen was observed as a high-brightness area before treatment, after treatment, this high-brightness area was observed to be thicker and surround the entire lumen. It was shown that simply occluding the skin and preventing water evaporation from the skin, rather than actively supplying water to the skin with water-soaked cotton wool as in Test Example 1, resulted in hydration and swelling of the stratum corneum inside the pore. However, in a horizontal section 15 μm deeper from the granular cell layer, the increase in brightness of the stratum corneum at the boundary with the pore lumen was slight, and the ring-shaped structure was barely discernible (Figure 4(B)). In a horizontal section 15 μm deeper than the stratum corneum, no increase in brightness was observed for the contents inside the pore (keratin plugs) present in the lumen (Figures 3 and 4).

[0046] The hydration and swelling caused by cotton wool soaked in distilled water is thought to be an excessive water load compared to occlusion treatment using a water-impermeable membrane, and the difference between the images taken in Test Example 1 (Figures 1 and 2) and Test Example 2 (Figures 3 and 4) is thought to be due to the difference in the degree of swelling or hydration of the pore stratum corneum. Swelling and hydration of the stratum corneum in the pore lumen occurred relatively easily at shallow depths in the granular cell layer immediately below the stratum corneum (Fig. 3), and more aggressive swelling or hydration was thought to result in swelling of the stratum corneum at deeper depths (an additional 15 μm deeper) (Fig. 2).

[0047] (Test Example 3) As shown in Test Examples 1 and 2, analysis of images of pores captured using a reflective confocal laser microscope confirmed that pore hydration or swelling increases the brightness of the pore stratum corneum, the depth of the swollen stratum corneum with increased brightness increases, the thickness of the pore stratum corneum increases, and the brightness of keratinocytes increases (see Figures 5 and 6). In particular, the increase in brightness of the pore stratum corneum and the appearance of a ring structure associated with the increase in thickness of the pore stratum corneum due to pore hydration or swelling were characteristic. Therefore, we investigated the setting of parameters that indicate the degree of hydration or swelling of pores, which quantifies the appearance of ring structures (see Figure 7).

[0048] In a pore image captured using a reflective confocal laser microscope, a closed curve is drawn on the image along the lumen wall at the transition from the pore lumen (dark area) to the surrounding pore stratum corneum (relatively bright). A second curve is then drawn 30 μm outward from this curve. The region between these two curves is designated as region of interest A (ROIA), and the average brightness within it is designated as mean brightness value A (Figure 7). Draw a third closed curve 30 μm further outward from the second curve, and define the region between the second and third curves as region of interest B (ROIB). The average brightness within ROIB is defined as average brightness value B (Figure 7).

[0049] Even when the laser power of the reflective confocal laser microscope light source is constant, the brightness and contrast of the acquired image fluctuate greatly, reflecting individual differences in skin optical properties such as melanin, and laser attenuation due to imaging depth. Accordingly, the average brightness value A also fluctuates significantly and is unstable. To correct for this and stabilize it, it is preferable to obtain a normalized value by dividing by the average brightness value B, and use this normalized value as the pore swelling degree, which can then be used to evaluate the hydration or swelling state of the pore stratum corneum (Figure 7). By performing this image processing, a stable pore swelling index can be obtained regardless of the laser power or the optical properties of the skin. Setting of the region of interest and calculation of the average brightness can be performed using known image analysis software (e.g., ImageJ, manufactured by the National Institutes of Health, USA).

[0050] After washing their faces, subjects were allowed to rest for at least 20 minutes in a standard environment for skin physiological measurements (a thermostatic chamber with a temperature of 21.8°C and a relative humidity of 50%). Then, using a reflectance confocal laser microscope, tomographic images of three pores on the cheek were taken, one just below the stratum corneum and the other 15 μm below. The pore swelling index was measured at each depth using the above method, and the mean and standard deviation were calculated. The results were 0.83 ± 0.06 (mean ± standard deviation) just below the stratum corneum and 0.83 ± 0.02 (mean ± standard deviation) at a depth of 15 μm, demonstrating consistent pore swelling index regardless of measurement depth. A pore swelling index of 1, which is determined to be three or more standard deviations away from the mean value and to be a definite image change (appearance of a ring), was set as the standard value for evaluating the hydration or swelling state of the pore stratum corneum. A pore swelling index of 1 or more was defined as the swelling region, and a index of 0.9 to less than 1 was defined as the gray zone. When evaluating the pores in Figure 2, which were in an overly hydrated environment, both depths were determined to be swollen (see Figure 8). When evaluating the pores in Figure 4, which were in an obstructed environment, they were determined to be swollen just below the stratum corneum and in the gray zone at a depth of 15 μm (see Figure 8).

[0051] As described above, according to the present invention, the hydration or swelling state of the pore stratum corneum can be accurately evaluated from the brightness of an image of the stratum corneum located at the boundary between the keratinocytes (living cells) that make up the pore and the pore lumen.

Claims

1. A method for evaluating the hydration or swelling state of a pore stratum corneum, comprising: The subject's pore stratum corneum was photographed using an optical microscope. determining at least one feature value related to the pore stratum corneum selected from the group consisting of brightness of the swollen stratum corneum in the pore, depth of the swollen stratum corneum, thickness of the swollen stratum corneum, and brightness of the keratinocyte plug based on the brightness of the captured image; Evaluating the hydration or swelling state of the pore stratum corneum of the subject using the feature amount as an index. A method for evaluating the hydration or swelling state of the stratum corneum.

2. The method of claim 1 , wherein the optical microscope is a confocal laser scanning microscope.

3. The method according to claim 1 or 2, wherein a feature reflecting the hydration or swelling state of the stratum corneum is determined from image brightness information of the area of the captured image where the stratum corneum is present, and the hydration or swelling state of the stratum corneum is evaluated using the feature as an index.

4. The method according to claim 3, wherein the image brightness of a portion where the stratum corneum pores are present is normalized by the image brightness of a portion where the stratum corneum pores are not present.

5. The method according to claim 1 or 2, wherein the hydration or swelling state of the stratum corneum pores on the cheeks of the subject is evaluated.

6. The method according to claim 1 or 2, wherein the pore stratum corneum of a subject to be evaluated to which moisture has been actively added is imaged using an optical microscope, the images taken before and after the active addition of moisture are compared, and the change in image brightness at the location of the pore stratum corneum due to the active addition of moisture is correlated with the change in the feature determined based on the image brightness.

7. 3. The method according to claim 1 or 2, wherein an optical microscope is used to capture images of the stratum corneum of a subject whose evaporation of water from the skin to the external environment has been obstructed, the images captured before and after the obstruction of water evaporation are compared, and correlation is made between how the image brightness at the location of the stratum corneum changes due to the obstruction of water evaporation and how the feature determined based on the image brightness changes.

8. The method according to claim 1 or 2, wherein the hydration or swelling state of the pore stratum corneum is evaluated by confirming the appearance of a white ring-shaped area around the pore in a horizontal cross-sectional image of the subject's pore stratum corneum and determining the brightness characteristic of the swollen stratum corneum.

9. The method according to claim 1 or 2, wherein the hydration or swelling state of the pore stratum corneum is evaluated by measuring the depth from the skin surface at which a white ring-shaped area around the pore is observed in a horizontal cross-sectional image of the subject's pore stratum corneum, and determining a characteristic value of the depth of the swollen stratum corneum.

10. The method according to claim 1 or 2, wherein the hydration or swelling state of the pore stratum corneum is evaluated by measuring the width of a white ring-shaped area present around the pore in a horizontal cross-sectional image of the subject's pore stratum corneum to determine a characteristic value of the swollen stratum corneum thickness.

11. The method according to claim 1 or 2, wherein the hydration or swelling state of the pore stratum corneum is evaluated by measuring the brightness of the keratinocyte plugs in the pores in a horizontal cross-sectional image of the subject's pore stratum corneum and determining the brightness feature of the keratinocyte plugs.

12. Using an optical microscope, images of the subject's pore stratum corneum were taken at regular depths from the skin surface. From the captured image, information on the image brightness of the area where the pore stratum corneum is present is obtained for each depth, The method according to claim 1 or 2, wherein the hydration or swelling state of the stratum corneum extending from the surface of the skin to the interior of the skin is evaluated from the acquired information.

13. For the pore stratum corneum in a hydrated or swollen state, reference values are set for the brightness of the pore stratum corneum in the captured image, the depth of the swollen stratum corneum where the brightness has increased, the thickness of the pore stratum corneum, and the brightness of the keratinocyte plug, In an image of the pore stratum corneum of the subject, when at least one feature selected from the group consisting of the brightness of the pore stratum corneum, the depth of the swollen stratum corneum with increased brightness, the thickness of the pore stratum corneum, and the brightness of the keratinocyte plug reaches the reference value, the pore stratum corneum of the subject is evaluated to be in a hydrated or swollen state.

3. The method according to claim 1 or 2.

14. A method for evaluating the performance of an article, comprising having a subject wear one type of article selected from the group consisting of masks, rubber gloves, absorbent articles, steam heating devices, and wound protection materials, evaluating the hydration or swelling state of the stratum corneum using the method described in claim 1 or 2, and evaluating the effect of wearing the article on the stratum corneum.

15. 3. A device for evaluating the hydration or swelling state of a pore stratum corneum, used in the method according to claim 1 or 2, comprising: The device stores information relating to the correlation between at least one feature quantity of the stratum corneum selected from the group consisting of brightness of the swelled stratum corneum in the pore, depth of the stratum corneum, thickness of the stratum corneum, and brightness of the keratinocyte plug, which is determined based on the brightness of the stratum corneum obtained from an image captured by an optical microscope, and the hydration or swelling state of the stratum corneum, and is equipped with a calculation means for evaluating the hydration or swelling state of the stratum corneum of the subject using the feature quantity as an index based on the information relating to the correlation. A device for evaluating the hydration or swelling state of the stratum corneum.

16. A system for evaluating the hydration or swelling state of a pore stratum corneum, which is used in the method according to claim 1 or 2, A server that communicates via a network is included, The server stores information on the correlation between at least one feature quantity of the stratum corneum selected from the group consisting of brightness of the swelled stratum corneum in the pore, depth of the stratum corneum, thickness of the stratum corneum, and brightness of the keratinocyte plug, which is determined based on the brightness of the stratum corneum obtained from an image captured by an optical microscope, and the hydration or swelling state of the stratum corneum, and is equipped with a calculation means for evaluating the hydration or swelling state of the stratum corneum of the subject based on the information on the correlation and using the feature quantity as an index. A system for assessing the hydration or swelling state of the stratum corneum.

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