JP7564429B2 - How to evaluate wrinkles - Google Patents

Description

The present invention relates to a method for evaluating wrinkles.

When facial expressions change, the action of facial muscles causes the skin surface to bend, which can result in the formation of temporary wrinkles on the skin surface or the accentuation of existing wrinkles. Temporary wrinkles (hereafter also referred to as crease lines) are most noticeable immediately after the expression disappears and usually remain for about an hour before gradually disappearing, but if they are repeatedly formed, they can easily become wrinkles that are constantly visible on the skin surface (so-called permanent wrinkles).

The process of crease formation is temporary, and it is believed that the physical properties of the stratum corneum play a major role in the structure of the skin.

Creases that occur due to changes in facial expression can be a cosmetic problem. Therefore, when developing cosmetics that suppress creases, it is important to properly evaluate the extent to which wrinkles are formed or accentuated when subjects change their facial expression.

Methods proposed for evaluating wrinkles when a subject changes facial expression include having the subject turn their gaze upward at a specified angle to the horizontal plane, causing wrinkles on the forehead, and then ranking and evaluating the wrinkles on the forehead according to the size, depth, shape, etc. of the wrinkles (Patent Document 1), and marking tracking points at specified intervals on the corners of the subject's eyes with a stamp or the like, capturing the movement of the tracking points with a high-speed camera when the subject changes facial expression, and analyzing this movement to calculate wrinkle parameters such as the wrinkle area and length, as well as the stress applied to the skin (Patent Document 2).

Patent No. 5538786 Patent No. 6251489

In conventional methods for evaluating wrinkles when a subject changes their facial expression, the evaluation targets are wrinkles that are a combination of newly formed creases or creases that accentuate existing wrinkles and existing wrinkles (fixed wrinkles), but the creases themselves are not evaluated. Therefore, it is not possible to accurately grasp the relationship between the formation or accentuation of crease wrinkles (hereinafter referred to as the wrinkle formation state) and the physical properties of the skin. Furthermore, evaluation of anti-wrinkle cosmetics is not performed from the perspective of inhibiting the formation of crease wrinkles themselves, and evaluation is limited to the difficulty of noticing wrinkles that are a combination of crease wrinkles and existing wrinkles.

In response to this, the object of the present invention is to enable accurate evaluation of the state of crease formation itself using a simple method. Furthermore, since the state of the stratum corneum can be easily improved with cosmetics compared to the dermis and facial muscles, the object of the present invention is to analyze the relationship between the state of crease formation itself and the properties of the stratum corneum, and ultimately to enable estimation of the properties of the stratum corneum from the state of crease formation.

The inventors of the present invention have come up with the idea that when creating wrinkles on the surface of the facial skin by a specific movement of the facial muscles, the state of formation of the crease wrinkles themselves can be accurately evaluated by taking facial images before and after the creating and subtracting the evaluation value of the wrinkles before creating from the evaluation value of the wrinkles after creating, and in this case, by creating a wrinkle score index in advance and determining the evaluation value of the wrinkles based on the wrinkle score index, the state of formation of wrinkles before and after creating can be easily evaluated, and have completed the present invention.

That is, the present invention provides a method for evaluating temporary wrinkles (i.e., crease wrinkles) formed or accentuated by bending of facial skin, comprising:
Taking facial images before and after wrinkle formation by moving the skin so that a predetermined position on the skin surface is displaced by a predetermined length and a predetermined time,
Based on a wrinkle score index that evaluates the state of wrinkle formation in a plurality of stages, a score value of the state of wrinkle formation is obtained for each of the face images before and after the wrinkle formation is induced;
To provide a method for evaluating crease wrinkles, in which the difference between the score value of the wrinkle formation state of a face image after the wrinkles have been trained and the score value of the wrinkle formation state of a face image before the wrinkles have been trained is used as an evaluation value of the crease wrinkles of the skin.

The present invention also provides a method for estimating the properties of the stratum corneum, which obtains a relational equation between the evaluation value of the skin creases obtained by the above-mentioned evaluation method and the stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties of the skin, and estimates the stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties of a subject from the evaluation value of the skin creases based on the relational equation.

The present invention further provides a cosmetic evaluation method in which evaluation values for skin creases obtained by the above-mentioned evaluation method are obtained before and after application of the cosmetic to the skin, and the effect of the cosmetic in inhibiting wrinkle formation is evaluated from the difference between the evaluation value after application of the cosmetic and the evaluation value before application of the cosmetic.

In addition, the present invention provides a method for obtaining evaluation values for skin creases obtained by the above-mentioned evaluation method before and after application of a cosmetic to the skin, and estimating the amount of change in stratum corneum thickness, the amount of change in stratum corneum moisture content, or the amount of change in stratum corneum physical properties from the difference between the evaluation values after application of the cosmetic and the evaluation values before application of the cosmetic.

According to the method for evaluating crease wrinkles of the present invention, the evaluation value of skin crease wrinkles is the difference between the score value of the face image after wrinkles have been trained and the score value of the face image before wrinkles have been trained, so that crease wrinkles can be distinguished from existing wrinkles and the state of formation of the crease wrinkles themselves can be evaluated. The evaluation value of skin crease wrinkles shows a high correlation with the properties of the stratum corneum (e.g., stratum corneum thickness, stratum corneum moisture content, stratum corneum flexibility, and other stratum corneum physical properties). Therefore, if a relational expression between the evaluation value of skin crease wrinkles and the properties of the stratum corneum is obtained in advance, it becomes possible to estimate the properties of the stratum corneum from the evaluation value of the crease wrinkles of the subject's skin.

In addition, by obtaining the evaluation values for the creases on the skin before and after the application of the cosmetic and taking the difference between them, it is possible to estimate the amount of change in the stratum corneum thickness, the amount of change in the moisture content of the stratum corneum, or the amount of change in the physical properties of the stratum corneum before and after the application of the cosmetic, and the difference in the evaluation values for the creases makes it possible to properly evaluate the effect of the cosmetic in inhibiting the formation of wrinkles.

The wrinkle-inhibiting effect of cosmetics is closely related to the change in stratum corneum thickness, stratum corneum moisture content, and stratum corneum physical properties, making it possible to examine the wrinkle-inhibiting effect of cosmetics in a short period of time, such as one week.

FIG. 1A is an explanatory diagram of a face image before wrinkles are formed. FIG. 1B is an explanatory diagram of wrinkle formation. FIG. 1C is an explanatory diagram of a face image after wrinkles have been formed. FIG. 2 is an example of a wrinkle score index. FIG. 3 is a graph showing the relationship between the stratum corneum thickness and the evaluation value of crease wrinkles. FIG. 4 is a graph showing the relationship between the flexibility of the stratum corneum and the evaluation value of creases. FIG. 5 is a graph showing the evaluation values of crease wrinkles for each type of skin classified into four types based on the stratum corneum thickness and flexibility. FIG. 6 is a graph showing the evaluation values of creases before and after application of a cosmetic material. FIG. 7 is a graph showing the relationship between the amount of change in stratum corneum thickness and the amount of change in the evaluation score of crease lines when a cosmetic material is applied for one week. FIG. 8 is a graph showing the relationship between the change in stratum corneum flexibility and the change in crease evaluation score when a cosmetic product is applied for one week. FIG. 9 is a graph showing the amount of change in the evaluation value of crease wrinkles for each type when changes in the stratum corneum after one week of cosmetic application are classified into four types in terms of stratum corneum thickness and stratum corneum flexibility.

The present invention will now be described in detail with reference to the drawings.
(How to evaluate creases)
The method for evaluating crease wrinkles of the present invention is a method for evaluating temporary wrinkles newly formed on the skin surface due to bending of the skin when facial expression changes, or temporary wrinkles formed so as to accentuate existing wrinkles. More specifically, it is a method for evaluating the formation state (number, length, width, depth, etc.) of temporary wrinkles formed by wrinkle training.

In the method of evaluating crease wrinkles of the present invention, first, the facial skin is moved so that a predetermined position on the skin surface is displaced by a predetermined length for a predetermined time to form a wrinkle. Here, the predetermined position is a reference position for moving the skin, and is preferably a part that moves easily due to the action of facial muscles. At the predetermined position, it is preferable to draw a mark using paint such as point makeup cosmetics such as eyeliner or eyebrow ink, or to attach a sticker as a mark. Alternatively, a characteristic part of the face such as the head of the eyebrow may be set as the predetermined position.

After determining the predetermined position that will be the reference for displacement, a facial image including that part is taken before the habit is shaped. For example, in the embodiment shown in FIG. 1A, a mark 1 with a diameter of 0.3 to 3 mm, preferably 0.5 to 2 mm, is drawn on the subject's eyebrow with eyeliner, and a facial image is taken with the subject's eyes closed (Image A).

Next, the facial muscles are moved to form wrinkles on the face. In this case, the degree of movement of the facial muscles is preferably set to a degree slightly less than the maximum amount that the subject can generally move, and is determined depending on which part of the face the predetermined position is set to. For example, in the above embodiment, as shown in FIG. 1B, when the subject moves mark 1 toward the head to form wrinkles on the forehead, the movement distance d of mark 1 is set to a predetermined value in the range of 0.5 to 2 cm, preferably 0.8 to 1.5 cm. More specifically, the subject wrinkles the forehead so that the position p1 of mark 1 after movement is a predetermined distance d from the position p0 of mark 1 when the eyes are closed in FIG. 1A. Then, it is preferable to maintain this state in which mark 1 has been moved for a predetermined time in the range of 10 seconds to 3 minutes, preferably 30 seconds to 1 minute and 30 seconds, to form wrinkles.

Next, the subject returns the facial muscles to the state before the crease, and a facial image after the crease is taken. Preferably, the subject performs a movement to relieve tension in the facial muscles, and after confirming that the mark has returned to the state before the crease is taken, a facial image is taken promptly. For example, in the above embodiment, as shown in FIG. 1C, the subject releases the tension in the facial muscles and closes the eyes, and preferably blinks several times to further relieve tension in the facial muscles. Then, after confirming that the mark 1 has returned to the position when the eyes are closed, a facial image of the subject is taken promptly, preferably within 5 seconds to 3 minutes, more preferably within 5 seconds to 30 seconds, and even more preferably within 5 seconds to 10 seconds (Image B). After the crease is creased, the crease gradually becomes thinner over time, but by taking an image promptly after the crease is creased, the correlation between the evaluation value of the crease according to the present invention and the stratum corneum thickness and stratum corneum physical properties can be increased.

As for the method of forming wrinkles, in addition to forming wrinkles on the forehead by bringing the eyebrows towards the head as in the above example, wrinkles can also be formed at the corners of the eyes by closing the eyes tightly, or nasolabial folds can be formed by drawing the corners of the mouth straight to the side by 1 to 2.5 cm on each side while making an "Ee" shape. There are no limitations on the way to create the facial expression as long as wrinkles are formed. Preferably, the wrinkles are formed using the facial muscles. In either case, the time for forming the wrinkles can be the same as when forming wrinkles on the forehead by bringing the eyebrows towards the head.

The camera for taking the image A before the curling and the image B after the curling is not limited to a particular type as long as it can take an image of the creases that can be visually confirmed, and may be, for example, a general digital camera, a still camera, a video camera, etc. The image taken by the camera may be a color image, a monochrome image, or any other type.
As the illumination light, for example, white light can be used.

In the present invention, a score value for the state of wrinkle formation in the above-mentioned images A and B is obtained based on a wrinkle score index that evaluates the state of wrinkle formation on a multiple-level scale.

Here, the wrinkle score index is obtained by taking face images of multiple people as subjects under the same photographing conditions as those of the above-mentioned images A and B, and ranking the wrinkle formation state of the face images into multiple stages, preferably 5 to 13 stages, and more preferably 7 to 11 stages. It is preferable that the score index describes the characteristics of the wrinkle formation state of each stage in words and lists representative face images. Note that the face images used to form the score index may be images before or after the wrinkle formation has been conditioned. In addition, in order to make the wrinkle formation state easier to understand, the face images used in the score index may be subjected to image processing such as multi-value processing and detection by filtering.
The score index may be created for each age group of subjects.

For example, the wrinkle score index shown in Figure 2 is a nine-level evaluation of the state of wrinkles on the faces of 48 people in their 30s to 50s immediately after they had trained themselves to wrinkle on their foreheads, with evaluation values ranging from 0 to 4, as shown below. The images were taken using a VISIA-CR made by Canfield Scientific.

[Wrinkle score index]
Score value 0: no wrinkles Score value 0.5: slight, unclear, shallow wrinkles Score value 1.0: small, shallow wrinkles Score value 1.5: shallow wrinkles Score value 2.0: medium wrinkles among shallow wrinkles Score value 2.5: less than three medium wrinkles Score value 3.0: three or more medium wrinkles Score value 3.5: less than three deep wrinkles Score value 4.0: three or more deep wrinkles

In the present invention, after obtaining the score values of the state of wrinkle formation in images A and B based on the wrinkle score index, the value obtained by subtracting the score value of image A from the score value of image B is set as the evaluation value of the crease wrinkles. Therefore, according to the present invention, the evaluation value of the crease wrinkles themselves can be obtained very simply.

As described below, the evaluation value of crease wrinkles has a high correlation with the stratum corneum thickness, stratum corneum moisture content, and stratum corneum physical properties, and is useful for evaluating the wrinkle formation suppression effect of cosmetics. It is also useful for knowing the state of the stratum corneum of the subject, and for knowing the changes in stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties caused by cosmetics. On the other hand, as mentioned above, there is no particular limitation on the type of camera used to capture the images before and after wrinkle formation. Therefore, for example, the subject can take images with a smartphone before and after wrinkle formation and send the images to a beauty advisor, and the beauty advisor can obtain the evaluation value of the subject's crease wrinkles based on the wrinkle score index, and from the evaluation value, the properties of the stratum corneum, such as the stratum corneum thickness and stratum corneum moisture content, can be obtained, and the results can be used to propose skin care.

As a method for evaluating the crease itself using image A and image B, it is possible to use a difference image between image B and image A, but forming the difference image requires precise alignment and image processing software. In contrast, the present invention, which performs visual evaluation using a score index, is advantageous in that it does not require precise alignment between image A and image B or image processing software to form a difference image, and the evaluation value of the crease itself can be easily obtained.

(Method of estimating the properties of the stratum corneum)
The evaluation value of crease wrinkles according to the present invention has a high correlation with stratum corneum thickness, stratum corneum moisture content, stratum corneum flexibility, etc. Therefore, by obtaining the evaluation value of crease wrinkles according to the present invention and the values of stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties of the skin from a plurality of subjects in advance and obtaining a regression equation as a relational equation between these, it is possible to estimate the stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties of the subject by obtaining the evaluation value of crease wrinkles of the subject.

For example, when the stratum corneum thickness of the foreheads of the aforementioned 48 subjects was measured, the stratum corneum thickness and the evaluation value of the crease wrinkles showed the relationship shown in FIG. 3, and there was a correlation (correlation coefficient R = 0.497). Therefore, the regression equation for estimating the stratum corneum thickness y from the evaluation value x of the crease wrinkles is y = 1.273x + 6.479
It can be seen that by calculating the regression equation, the stratum corneum thickness can be estimated by measuring the evaluation value of the crease for any subject.

When obtaining this regression equation, a method for measuring the stratum corneum thickness is preferable that can measure non-destructively, since it is possible to obtain the stratum corneum thickness in the facial area where the evaluation value of crease wrinkles was obtained. Examples of such a method include the Raman spectroscopy measurement method presented by S. Naito, S. Tokuhara, M. Igaki, Y. Masukawa at ISBS BESANCON Congress, 2009, and the Raman spectroscopy measurement method described in Patent Publication No. 5323600.

On the other hand, when the flexibility of the stratum corneum was measured for the above-mentioned 48 subjects, the flexibility of the stratum corneum and the evaluation value of the crease wrinkles showed the relationship shown in FIG. 4, and they had a correlation (correlation coefficient R=0.475). Therefore, the regression equation between the evaluation value of the crease wrinkles x and the flexibility of the stratum corneum y is y=18.257x-62.733.
Once calculated, the regression equation can be used to estimate the stratum corneum flexibility by measuring the evaluation value of creases for any subject.

The stratum corneum flexibility can be measured using a Venustron (manufactured by AXIOM) according to the method of Sakai et al. (Sakai S, Sasai S et al., Characterization of the physical properties of the stratum corneum by a new tactile sensor., Skin Res Technol. 2000; 6(3):128-134.). The Venustron is an instrument that brings a test substance into contact with a probe that vibrates at a constant frequency, and measures the softness by the amount of change in frequency (Δf (Hz)). The harder the test substance, the larger the Δf (change in the positive direction), and the softer the test substance, the smaller the Δf (change in the negative direction).

More specifically, for example, a Venustron probe is pressed into the measurement site on the subject's skin (probe frequency 50 Hz, maximum pressing depth 3 mm), and the change in frequency when the probe load pressure is 2 g is measured as the stratum corneum flexibility Δf (2 g).

The moisture content of the stratum corneum can be measured, for example, using a corneometer manufactured by Courage+Khazaka, SKICON manufactured by IBS, or by the method using Raman spectroscopy described in Japanese Patent No. 5288912. The moisture content of the stratum corneum is closely related to the flexibility of the stratum corneum.

In the present invention, the method for measuring the stratum corneum thickness, stratum corneum moisture content, and stratum corneum physical properties that show a correlation with the evaluation value of creases are not limited to the above-mentioned method.

From Figures 3 and 4, it can be seen that the thicker the stratum corneum is and the lower the flexibility (the harder the stratum corneum is), the higher the evaluation value of the skin crease wrinkles and the easier it is for crease wrinkles to form. This tendency can also be seen from Figure 5. That is, Figure 5 shows the average evaluation value of crease wrinkles for each type when the stratum corneum types of the above-mentioned 48 people are classified into four types from the viewpoint of stratum corneum thickness and stratum corneum flexibility: (i) thick stratum corneum/hard stratum corneum, (ii) thick stratum corneum/soft stratum corneum, (iii) thin stratum corneum/hard stratum corneum, and (iv) thin stratum corneum/soft stratum corneum from the viewpoint of stratum corneum thickness and stratum corneum flexibility. Here, for thick and thin stratum corneum, the average value of the stratum corneum thickness measurement value of the 48 people or more was defined as "thick" and the value below the average was defined as "thin". Similarly, for hard and soft stratum corneum, the average value of the stratum corneum flexibility measurement value of the 48 people or more was defined as "hard" and the value below the average was defined as "soft". From Figure 5, it can be seen that crease wrinkles are easier to form when the stratum corneum is thick and hard.

(Effect of cosmetics on preventing wrinkle formation)
As described above, the evaluation value of the present invention for crease wrinkles correlates with the physical properties of the stratum corneum, such as stratum corneum thickness, stratum corneum moisture content, and stratum corneum flexibility, etc. Therefore, when the wrinkle formation inhibitory effect of a cosmetic product is due to the function of the cosmetic product acting on the stratum corneum to reduce the stratum corneum thickness by improving stratum corneum thickening, which causes the stratum corneum to thicken, thereby increasing the stratum corneum moisture content, or improving the stratum corneum flexibility, it is considered that the wrinkle formation inhibitory effect of the cosmetic product can be evaluated by the evaluation value of the present invention for crease wrinkles.

From this perspective, Figure 6 shows the change in the evaluation score of forehead creases when two types of cosmetics, A and B, which have different ingredients and functions, were applied to the entire facial skin of subjects, with 0.8g of cosmetics A and 0.6g of cosmetics B applied twice a day for one week. The subjects in this case were 16 people in their 30s to 50s.

Cosmetic A: A cosmetic whose main ingredient is carbonic acid, which normalizes the turnover of the stratum corneum by maintaining the skin at a slightly acidic state.
Cosmetic B: A cosmetic whose main ingredient is a water-in-oil emulsion containing a moisturizing ingredient with excellent moisture retention ability in the water phase, which improves the moisture content of the skin and moisturizes the skin.

Figure 6 shows that the combined use of cosmetic A and cosmetic B has the effect of suppressing the formation of creases.

When the formation of creases is suppressed, the wrinkles that appear when changing facial expressions are reduced, and the subject and those around them are left with a more youthful appearance, so the effect of suppressing the formation of creases is important from a cosmetic standpoint.

In addition, if the cosmetic product's effect of suppressing the formation of creases continues, it is expected that fixed wrinkles will also be reduced, so in this respect too, the effect of suppressing the formation of creases is important from a cosmetic standpoint.

According to the present invention, it is possible to easily confirm the effect of suppressing the formation of creases, which is of great cosmetic importance. In particular, it is possible to evaluate the presence or absence and the degree of the effect of suppressing the formation of creases in a short period of one week.

Figure 7 plots the change in crease evaluation score and the change in stratum corneum thickness after one week of cosmetic application for the 16 subjects shown in Figure 6. In this case, the stratum corneum thickness was measured using Raman spectroscopy in the same way as the stratum corneum thickness shown in Figure 3, and the average of six measurements was plotted.

Figure 7 shows that there is a correlation (R = 0.552) between the change in stratum corneum thickness and the change in the evaluation score for crease wrinkles, and that a decrease in stratum corneum thickness makes crease wrinkles less noticeable.

Figure 8 plots the change in crease evaluation score and the change in stratum corneum flexibility after one week of cosmetic application for the 16 subjects shown in Figure 7. In this case, stratum corneum flexibility was measured using a Venastron method, similar to the stratum corneum flexibility shown in Figure 4.

Figure 8 shows that there is a correlation (R = 0.582) between the change in stratum corneum flexibility and the change in the evaluation score for creases, and that improving stratum corneum flexibility makes creases less noticeable.

Figure 9 shows the average evaluation value of crease wrinkles for each type of skin improvement pattern, when the results of the change in evaluation value of crease wrinkles due to one week application of the cosmetics of the 16 subjects shown in Figures 7 and 8 are classified into four types: (i) stratum corneum thickening and hardening, (ii) stratum corneum thickening and softening, (iii) improved stratum corneum thickening and hardening, and (iv) improved stratum corneum thickening and softening.

From Figure 9, it can be seen that subjects in whom both improved thickening and softening of the stratum corneum were observed showed a large change in the evaluation value of crease wrinkles. The change in the evaluation value of crease wrinkles is closely related to the change in stratum corneum thickening and softness, and it is possible to estimate whether the stratum corneum has thickened or whether its softness has improved from the change in the evaluation value of crease wrinkles. Therefore, measuring the evaluation value of crease wrinkles of the present invention before and after application of a cosmetic product and evaluating the cosmetic product by taking the difference between the two values will be useful in developing a cosmetic product that prevents thickening of the stratum corneum and improves its softness.

1 Mark 2 Wrinkle d Mark movement amount

Claims (6)

A method for evaluating temporary wrinkles (hereinafter referred to as crease wrinkles) formed or accentuated by bending of facial skin, comprising:
Taking facial images before and after the subject moves the skin so that a predetermined position on the skin surface is displaced by a predetermined length and for a predetermined time,
Based on a wrinkle score index which ranks the state in which wrinkles are formed or emphasized (hereinafter referred to as wrinkle formation state) in 5 or more stages, a score value of the wrinkle formation state is obtained for each of the face images before and after the wrinkle formation;
The method for evaluating crease wrinkles uses the difference between the score value of the wrinkle formation state of a face image after the wrinkles have been trained and the score value of the wrinkle formation state of a face image before the wrinkles have been trained as an evaluation value of the skin crease wrinkles. The evaluation method according to claim 1, in which, after the wrinkles have been formed, the subject performs a movement that relaxes the tension in the facial muscles, and a facial image after the wrinkles have been formed is taken within 5 seconds to 3 minutes after the predetermined position of the skin surface has returned to the position before the wrinkles have been formed. A method for estimating the properties of the stratum corneum, which obtains a relational expression between an evaluation value of skin creases obtained by the evaluation method of claim 1 and the stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties of the skin, and estimates the stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties of a subject from the evaluation value of the creases of the skin of the subject based on the relational expression. The estimation method according to claim 3, wherein the physical property of the stratum corneum is flexibility. A method for evaluating a cosmetic product, comprising obtaining evaluation values for skin creases using the evaluation method described in claim 1 before and after application of the cosmetic product to the skin, and evaluating the effect of the cosmetic product in inhibiting wrinkle formation from the difference between the evaluation value after application of the cosmetic product and the evaluation value before application of the cosmetic product. A method for estimating the amount of change in stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties by obtaining evaluation values for skin creases before and after application of a cosmetic product to the skin using the evaluation method described in claim 1, and estimating the amount of change in stratum corneum thickness, stratum corneum moisture content, or stratum corneum physical properties from the difference between the evaluation values after application of the cosmetic product and the evaluation values before application of the cosmetic product.

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