Itching evaluation method

Abstract

To provide a technology of evaluating itching felt by skin of a subject by bringing a tip of fiber into contact with the skin.SOLUTION: An itching evaluation method includes a contact step of bringing a tip of fiber into contact with skin of a subject by applying a load to the skin, an acquisition step of acquiring presence or absence or a degree of itching felt by the skin of the subject in the contact step, and an evaluation step of evaluating itching felt by the skin by using an acquisition result in the acquisition step.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an itching evaluation method for evaluating itching felt on the skin.

Background Art

[0002] There is a technique of attaching an electrode part to the skin and applying an electrical stimulus while displacing it to measure the skin sensory threshold (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of Patent Document 1, an electrical stimulus is applied to the skin of a subject to measure the skin sensation (itching). However, as cases where a subject feels itching on the skin in daily life, there are many cases caused by contact of hair with the skin, contact of clothing, or contact of mask fibers due to wearing a mask. Measurement of itching in a state close to an actual case where a subject feels itching on the skin has not been performed.

[0005] The present invention has been made in view of the above problems, and relates to a technique that enables evaluation in a state close to a case where a subject feels itching on the skin in daily life.

Means for Solving the Problems

[0006] The present invention relates to an itching evaluation method including a contact step of bringing the tip of a fiber into contact with the skin of a subject while applying a load, an acquisition step of acquiring the presence or degree of itching felt by the subject on the skin in the contact step, and an evaluation step of evaluating the itching felt on the skin using the acquisition result of the acquisition step. In this specification, the "itching evaluation method" means evaluating itching felt on the skin for non-medical purposes, and includes evaluations that can be performed by evaluators other than experts.

[0007] Further, the present invention relates to an instrument for evaluating itching felt on the skin, comprising a fiber that comes into contact with the skin and a support member that supports the fiber, wherein the minimum load in the major axis direction required for the fiber to bend is 4.9×10 -5 [N] to 1.2×10 -2 [N].

Effects of the Invention

[0008] According to the method provided by the present invention, the tip of the fiber is brought into contact with the skin of the subject while applying a load, the presence or degree of itching felt by the subject on the skin due to the contact is acquired, and the itching felt on the skin is evaluated using the acquisition result. Therefore, it is possible to evaluate itching in a state close to the state where the subject feels itching in daily life.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. <Itching Evaluation Instrument> First, the itching evaluation instrument 10 used in the itching evaluation method of the present embodiment (hereinafter, may also be expressed as this method) will be described with reference to FIGS. 1(a) and 1(b). The itching evaluation device 10 is a device (skin irritation-providing device for itching evaluation) for evaluating itching that may occur by bringing a fiber into contact with the skin to irritate the skin (specifically, the presence or degree of itching felt on the skin). As shown in Fig. 1(a), the itching evaluation device 10 is composed of a fiber 11 that contacts the skin and a support member 12 that supports the fiber 11. The load required for the fiber 11 to bend in the major axis direction is predetermined. Since this load can be regarded as the load applied from the fiber 11 to the skin in a state where the fiber 11 starts to bend while contacting the skin, it is hereinafter also referred to as the contact load. As shown in Fig. 1(a), the support member 12 is marked with No. (drawing number 13) indicating the fiber number. As shown in Fig. 1(b), the itching evaluation device 10 has eight (eight types) support members 12 marked with different fiber numbers. The contact load of the fiber 11 varies depending on the fiber number. As shown in Fig. 1(b), when the stored support member 12 is taken out (in the case of Fig. 1(b), in the state where the support member No. 3 is taken out), the contact load is described below the position where the support member 12 was placed. In the case of Fig. 1(b), since it is described as 0.04 [g], the force required for the fiber 11 supported by the support member 12 of No. 3 to bend in the major axis direction is 0.04 [gf] (3.9×10 -4 [N]). In the present embodiment, as a whole of a plurality of fibers 11 of the itching evaluation device 10, the minimum load in the major axis direction required for the fiber 11 to bend is from 0.005 [gf] to 1.2 [gf] (4.9×10 -5 [N] to 1.2×10 -2 [N]), preferably from 0.007 [gf] to 0.7 [gf] (6.9×10 -5 [N] to 6.9×10 -3 [N]), more preferably from 0.007 [gf] to 0.2 [gf] (6.9×10 -5 [N] to 2.0×10 -3As described in [N], the contact load of each fiber 11 is set. Although details will be described later, it is a value based on the evaluation results obtained from multiple subjects. By setting the minimum load within such a range, it is possible to apply a load suitable for itching evaluation in the longitudinal direction of the fiber 11 with the tip of the fiber 11 in contact with the skin, and it is possible to easily confirm by the deflection of the fiber 11 that such a load is applied to the skin. The fibers 11 are made of the same material but have different diameters, regardless of the fiber number. Due to the different diameters, the loads required for the fibers to bend in the longitudinal direction vary depending on the fiber number. Table 1 shows the fiber numbers and the loads (contact loads) required for the fibers to bend in the longitudinal direction.

[0011]

Table 1

[0012] For example, since No. 4 is described as the fiber number on the support member of the evaluation instrument 10 shown in Fig. 1(a), the load required for the fiber 11 of this evaluation instrument 10 to bend in the longitudinal direction is 0.07 [gf] (6.9×10 -4 [N]). Note that evaluation instruments 10 provided with fibers 11 having contact loads of 0.005 [gf], 0.007 [gf], 0.2 [gf], 0.7 [gf], and 1.2 [gf] respectively may be prepared. In the present embodiment, the material of the fiber 11 is resin, and specifically, nylon can be used. One evaluation instrument 10 has one fiber 11. By using one fiber 11 in contact with the skin, the precision of itching evaluation can be improved. Further, each fiber 11 is a so-called monofilament made of a single fiber. By using a monofilament, it is easy to evaluate an itching sensation similar to that when fibers of clothing or masks come into contact with the skin in daily life. The diameter of the fiber 11 is from 10 [μm] to 280 [μm], preferably from 20 [μm] to 240 [μm], more preferably from 30 [μm] to 200 [μm]. By setting the diameter within such a range, it is easy to realize a contact load suitable for itching evaluation. In this embodiment, the material of the fiber 11 is nylon, but it is not limited to this, and synthetic resins such as polyester, polypropylene, polyvinyl chloride, and acrylic can be widely used. Moreover, not only artificial fibers using synthetic resins or the like, but also natural fibers such as human hair can be used.

[0013] Next, with reference to FIGS. 2(a) to (e), a method of bringing the fiber 11 of the evaluation instrument 10 into contact with the skin of the subject will be described. As shown in FIGS. 2(a) to (d), the evaluator holds the support member 12 of the evaluation instrument 10 and brings the fiber 11 into perpendicular contact with the skin of the subject. In this embodiment, although details will be described later, the skin that the tip of the fiber 11 contacts is the face, for example, the jaw, around the mouth, or the cheek. As shown in FIGS. 2(a) to (d), when bringing the tip of the fiber 11 into contact with the skin of the subject, the evaluator does so while holding the support member 12. In this method, although details will be described later, after bringing the tip of the fiber 11 into contact with the skin, a load is applied in the major axis direction while keeping the tip in contact to buckle the fiber 11, and then the load on the buckled fiber 11 is removed. If there is no support member 12 and the fiber 11 is directly held and brought into contact with the skin, the buckling location will vary depending on the location where the fiber 11 is held, and it may not be possible to perform a consistent evaluation. Therefore, it is preferable to provide the support member 12 and configure it to apply a load from a fixed position of the fiber 11.

[0014] FIG. 2(a) is a diagram showing a state where the tip of the fiber 11 is in contact with the skin. Here, from the state where the evaluator holds the support member 12 such that the tip of the fiber 11 is located about 2 cm away from the skin, the tip of the fiber 11 is brought into perpendicular contact with the skin as shown in FIG. 2(a) at a speed of 1.6 [cm / sec] to 2.5 [cm / sec]. By contacting at such a speed, an appropriate stimulus can be given to the skin, making it easier to evaluate itching. FIG. 2(b) is a diagram showing the process of applying a force until the tip of the fiber 11 contacts the skin in FIG. 2(a) and the fiber 11 bends at about a right angle. By applying a force until the fiber 11 bends, it can be easily confirmed by the bending of the fiber 11 that a predetermined contact load is applied to the skin. Specifically, a force is applied until it bends from about 60° to 90° without moving the tip of the fiber 11 from the position (predetermined position) where it was brought into contact in FIG. 2(a). Here, what it means to bend from about 60° to 90° will be described with reference to FIG. 2(e). Figure 2(e) is an enlarged view of Figure 2(b). The dashed lines in the figure indicate the state where no force is applied to the fiber 11, and the solid lines indicate the state where a force is applied to the fiber 11 and it is bent (the state of Figure 2(b)). The two-dot chain line indicates the state of the fiber 11 when the load on the fiber 11 is increased from the state of Figure 2(b) and it is bent by about 90°. As shown in Figure 2(e), the proximal end side of the fiber 11 protrudes axially from the support member 12, and by bending the fiber 11, it shows a first curvature in a certain direction. Further, at the distal end side, at the bending point where it is bent with the smallest radius of curvature (i.e., most sharply), it shows a second curvature in the opposite direction, and the tip of the fiber 11 is lightly abutted against the skin and is in a state of being rotationally displaceably constrained. Between the first curvature and the second curvature, there is an inflection point where the bending direction is reversed. The two dashed-dotted lines shown in Figure 2(e) indicate virtual lines (reference lines) for explaining the bending angle of the fiber 11, showing the tangent of the fiber 11 at the inflection point and the tangent of the fiber 11 at the tip. And the angle formed by the two tangents is called the bending angle of the fiber 11. The bending angle is 180° when the fiber 11 is straight (the dashed line in the figure), and in the slightly bent state as shown by the solid line in Figure 2(e), it is a bending angle greater than 90° and less than 180°. And as the load on the fiber 11 is increased, the radius of curvature of the fiber 11 becomes smaller. In the example shown by the two-dot chain line in Figure 2(e), it is about 90°, and the fiber 11 may be sharply bent until the load on the fiber 11 is further increased and the bending angle becomes about 60°. In the present embodiment, it is preferable to bend the fiber 11 until the bending angle of the fiber 11 becomes from 60° to 90°. By applying a load to the fiber 11 until such a bending angle is reached, it is possible to satisfactorily simulate the state where the tips of the hair, etc. hit the skin and give a prickling itch. By keeping the tip of the fiber 11 at a predetermined position while applying such a load, an appropriate stimulus can be given to the skin, making it easier to evaluate itching. Also, it is preferable to apply a force so that the fiber 11 bends between 0.5 [sec] and 2 [sec], preferably between 1 [sec] and 1.5 [sec] after the tip of the fiber 11 comes into contact with the subject's skin. By applying a force so that the fiber 11 bends in this way, it is easy to stimulate the skin and easy to evaluate itching.

[0015] Figure 2(c) is a view in which the fiber 11 is lifted from the bent state in Figure 2(b) until it becomes straight without the tip leaving. Here, while keeping the fiber 11 bent at the position (predetermined position) where contact was made in Figure 2(a), the force is released so that it is in a state without bending. By keeping the tip of the fiber 11 at the predetermined position while releasing the force in this way, an appropriate stimulus can be given to the skin, and it becomes easy to evaluate itching. Also, it is preferable to release the force so that the bending of the fiber 11 disappears between 0.5 [sec] and 2 [sec], preferably between 1 [sec] and 1.5 [sec]. By releasing the force of the fiber 11 bent in this way, an appropriate stimulus can be given to the skin, and it becomes easy to evaluate itching.

[0016] Figure 2(d) is a view in which the fiber 11 that has become straight in Figure 2(c) is separated from the skin. Here, the tip of the fiber 11 is separated from the skin at a speed of 1.6 [cm / sec] to 2.5 [cm / sec] from the position (predetermined position) where contact was made in Figure 2(a). By doing so, an appropriate stimulus can be given to the skin, and it becomes easy to evaluate itching. As described above, any of the operations of bringing the fiber 11 into contact with the subject's skin, bending it, restoring the bend, and separating it from the subject's skin should be performed slowly. In this method, itching is evaluated using the evaluation instrument 10 shown in Figures 1(a) and 1(b) as shown in Figures 2(a) to 2(d).

[0017] <Itching Evaluation Method> This method will be described using the flowchart showing the itching evaluation method (this method) of the present embodiment shown in Figure 3. As shown in Figure 3, this method is composed of a contact step (step S100), an acquisition step (step S110), and an evaluation step (step S120).

[0018] The contact step (step S100) is a step in which the evaluator applies a load to the tip of the fiber 11 and brings it into contact with the subject's skin. The tip of the fiber 11 refers to a cross-section including the diameter of the fiber 11, which may or may not extend in a direction perpendicular to the axis of the fiber 11, and may be a curved surface rather than a flat surface. By making the tip of the fiber 11 planar, it is easy to simulate the tip of the actual fiber that causes itching. The skin of the subject may be any part of the body, but the skin of the face, which is considered to be prone to itching, is preferred. In particular, the sides of the mouth, the area between the mouth and the nose, the chin under the mouth, and the cheeks are preferred. In this embodiment, the tip of the fiber 11 is brought into contact with the skin of the sides of the mouth (the corners of the mouth), the chin, and the cheeks, and the evaluation results are compared. Applying a load and bringing it into contact means that, as shown in FIG. 2(a), from the state where the tip of the fiber 11 is brought into contact with the skin perpendicularly, a force is applied in the vertical direction as shown in FIG. 2(b) until the fiber 11 bends at about a right angle, and in any case of the process of removing the force so that the fiber 11 becomes straight as shown in FIG. 2(c) from the state of FIG. 2(b) is included.

[0019] The acquisition step (step S110) is a step in which the evaluator acquires the presence or degree of itching felt by the subject on the skin in the contact step. The presence or absence of itching felt on the skin is determined by whether the subject feels itchy or not itchy when the fiber 11 is brought into contact with the skin under load. On the other hand, the degree of itching felt on the skin is the degree of itching felt by the subject when the fiber 11 is brought into contact with the skin under load, and is obtained by having the subject indicate (answer or report) the degree or stage of the itching felt. When obtaining the degree of itching by quantifying it, for example, it is represented by an index (score) at a predetermined stage. In this embodiment, the degree of itching is represented by an index in five stages: 1. Not itchy at all, 2. Not very itchy, 3. Slightly itchy, 4. Itchy, 5. Very itchy. The subject is asked to answer which stage it corresponds to, and the answer is obtained. Also, as a method of obtaining the degree of itching based on the quantified index, it may be performed using a Visual Analog Scale (VAS). A scale of a predetermined length (for example, 10 cm) is prepared. For example, the left end is set as not itchy at all and the right end is set as very itchy, and the degree of itching may be obtained by having the subject specify at what position on the scale the itching felt is.

[0020] The evaluation step (step S120) is a step in which an evaluator evaluates the itching felt by the subject on the skin using the acquisition result of the acquisition step. The evaluation of the itching felt on the skin is to evaluate, for example, how itchy the subject feels when a certain amount of force is applied to the fiber 11, how itchy the subject feels when the fiber 11 of a certain diameter comes into contact with the skin, and how itchy the subject feels depending on the position on the skin. Note that at least one or more of the contact step, the acquisition step, and the evaluation step may be performed by the subject himself / herself. That is, each step may be performed by the same person, the evaluator and the subject. However, if the subject performs it himself / herself, there is a possibility that the objectivity of the evaluation may decrease. For example, if the subject performs the acquisition step, it will be information acquisition in a state where the subject knows how the fiber 11 is brought into contact with the skin, so there is a risk that the presence or degree of itching felt on the skin cannot be accurately obtained. From this point of view, it is preferable to perform each step with a third party other than the subject as the evaluator.

[0021] Next, the evaluation content performed will be described. <Evaluation Case 1> A case (referred to as Case 1) will be described where the presence or absence or degree of itching is obtained for two states of the skin, namely the bare skin state and the state with a topical skin agent applied, and evaluation is performed using the obtained results of both states. By evaluating the two states of the skin, namely the bare skin state and the state with a topical skin agent applied, in addition to the evaluation of the type (contact load) of the fiber 11 and the evaluation of itching according to the skin site, it is also possible to evaluate the difference in itching (itching suppression effect by the topical skin agent) due to applying the topical skin agent. A flowchart for the case of evaluating the two states of the skin, namely the bare skin state and the state with a topical skin agent applied, is shown in FIG. 4. Steps S150 and S160 shown in FIG. 4 are steps performed in the bare skin state, and steps S170 and S180 are steps performed in the state with a topical skin agent applied. Also, steps S150 and S170 are the same steps as step S100 in FIG. 3, and steps S160 and S180 are the same steps as step S110 in FIG. 3.

[0022] <Evaluation Conditions> Subjects: 6 people Measurement sites: Three sites on the left and right of the mouth, jaw, and cheeks of the face, for a total of six sites. The measurement sites are shown in FIG. 5. Skin condition: After washing the face and allowing 15 minutes for acclimation, the first contact step and the first acquisition step are performed in the bare skin state. Then, after applying a topical skin agent (0.2 g) and leaving it for 3 hours, the second contact step and the second acquisition step are performed. Topical skin agent: A UV preparation containing powder Evaluation method: A 5 - level score of 1. Not itchy at all, 2. Not very itchy, 3. Slightly itchy, 4. Itchy, 5. Very itchy. An image diagram of the evaluation sheet is shown in FIG. 6.

[0023] FIG. 7(a) is a graph showing the evaluation results of the cheek in the bare skin state, FIG. 7(b) is a graph showing the evaluation results of the mouth area in the bare skin state, and FIG. 7(c) is a graph showing the evaluation results of the jaw in the bare skin state. The horizontal axis represents the value of the contact load, and the vertical axis represents the itching score. From the graphs of FIGS. 7(a) to 7(c), when averaging all six subjects, at the mouth, itching begins to be felt (average evaluation of 2 or more) due to contact (stimulation) of the fiber 11 with a contact load ranging from 0.008 [gf] to 0.6 [gf] (7.8×10 -5 [N] to 5.9×10 -3 [N]), and it can be seen that itching is clearly felt (average evaluation of 3 or more) due to contact (stimulation) of the fiber 11 with a contact load ranging from 0.02 [gf] to 0.07 [gf] (2.0×10 -4 [N] to 6.9×10 -4 [N]). Also, when averaging all subjects, at the jaw, itching begins to be felt (average evaluation of 2 or more) due to contact (stimulation) of the fiber 11 with a contact load less than 0.008 [gf] to more than 0.6 [gf] (less than 7.8×10 -5 [N] to more than 5.9×10 -3 [N]), and it can be seen that itching is clearly felt (average evaluation of 3 or more) due to contact (stimulation) of the fiber 11 with a contact load ranging from 0.008 [gf] to 0.16 [gf] (7.8×10 -5 [N] to 1.6×10 -3 [N]). For some subjects, at the cheek as well, it can be seen that itching is clearly felt due to contact (stimulation) of the fiber 11 with a contact load ranging from 0.008 [gf] to 0.6 [gf] (7.8×10 -5 [N] to 5.9×10 -3 [N]). From this evaluation result, the minimum load in the major axis direction applied to the fiber 11 for evaluating itching is preferably from 0.007 [gf] to 0.7 [gf] (6.9×10 -5 [N] to 6.9×10 -3 [N]) compared to the load range where itching was felt (average evaluation of 2 or more) at the jaw, which was a result where itching was relatively easily felt. More preferably, it is from 0.008 [gf] to 0.16 [gf] (7.8×10 -5 [N] to 1.6×10 -3 [N]) compared to the load range with an average evaluation of 3 or more, which is an evaluation of clearly feeling itching. Also, in the case of the mouth, the minimum load is preferably 0.008 [gf] to 0.6 [gf] (7.8×10 -5 [N] to 5.9×10 -3It can be said that it is in the range of 0.02 [gf] to 0.07 [gf] (2.0×10 -4 [N] to 6.9×10 -4 [N]) rather preferably from the load range with an average evaluation of 3 or more, which is an evaluation of clearly feeling itching.

[0024] Figure 8(a) shows the average value of the evaluation results of 6 subjects for the bare skin state of the cheek (before application) and after applying the topical skin preparation (3 hours after application) (hereinafter simply referred to as the average value). Figure 8(b) shows the average value for the bare skin state of the mouth corner (before application) and after applying the topical skin preparation (3 hours after application). Figure 8(c) is a graph showing the average value for the bare skin state of the jaw (before application) and after applying the topical skin preparation (3 hours after application). The horizontal axis indicates the value of the contact load, and the vertical axis indicates the itching score. From the graphs of Figures 8(a) to 8(c), it can be seen that for any part, the itching level of the fiber 11 at the contact load where itching was felt in the bare skin state decreased after applying the topical skin preparation, although there were differences in the reduction level, and it can be seen that the itching score decreased. Therefore, although it has not been reduced to "not itchy", it can be seen that applying the topical skin preparation can slightly suppress the itching caused by the contact (stimulation) of the fiber 11. From Figures 7(a) to 7(c) and Figures 8(a) to 8(c), it can be seen that among the cheek, the mouth corner, and the jaw, the jaw has the highest itching score. Also, when the fiber 11 with a contact load of 0.07 [gf] (6.9×10 -4 [N]) is contacted, it can be seen that the itching score is high for any part (in the bare skin state).

[0025] <Evaluation Case 2> The presence or degree of itching for the state where multiple types of topical skin preparations are each applied is obtained, and the case of evaluating the itching suppression effect of each topical skin preparation (referred to as Case 2) will be described. In Case 2, based on the evaluation results of Case 1, the measurement is performed with the jaw, which had a high itching score in the bare skin state, as the measurement site. Also, for the fiber 11, the fiber number No. 4 (contact load: 0.07 [gf] (6.9×10 -4 [N])), which had a high itching score at the jaw site in the bare skin state, will be used.

[0026] <Measurement method> 1) Remove makeup around the jaw, wash with facial cleanser, and acclimatize for 10 minutes. 2) Mark two 3×3 cm measurement sites on both sides of the jaw as shown in Figure 9 with a marking pen. 3) Bring the tip of fiber 11 into vertical contact with the measurement site from a position 2.5 cm away from the skin over 1 - 1.5 seconds, apply a load over 1 - 1.5 seconds until fiber 11 bends, and remove the load over 1 - 1.5 seconds to eliminate the bend of fiber 11. Do this three times. Then, conduct itching evaluation (evaluation of the average itching sensation of the three times) using the Visual Analog Scale (VAS). For the 10 cm horizontal axis scale, the left end is "no itching" and the right end is "the strongest imaginable itching", and mark the level of the felt itching on the scale. Figure 10 shows an image diagram of the evaluation sheet. 4) Apply a single application amount of a topical skin agent (e.g., topical skin agent (1)) to the skin at the measurement site (e.g., the right - hand measurement site), bring fiber 11 into contact with the skin after application in the same method as in 3) above, and conduct evaluation using the Visual Analog Scale (application, measurement, and evaluation for the first application). 5) Apply an additional single application amount of the topical skin agent (e.g., topical skin agent (1)) to the skin where the evaluation of the first application has been completed, and conduct the same evaluation as in 4) above (application, measurement, and evaluation for the second application). Similarly, conduct application, measurement, and evaluation for the third application and the fourth application. 6) Apply a single application amount of a different topical skin agent (e.g., topical skin agent (2)) than those in 4) and 5) to the skin at a measurement site different from the measurement sites applied in 4) and 5) (e.g., the left - hand measurement site), and similarly conduct application, measurement, and evaluation for the first to fourth applications. 7) The measurement by the above measurement method is performed on 8 subjects. Since different types of topical skin agents are applied to the two measurement sites on the left and right, the number of samples N for one topical skin agent is 4. That is, in the case of this embodiment, for the topical skin agents (1) to (4), two types are performed per subject. Note that the itching VAS value of "0" for each application amount in FIGS. 11 to 13 is the itching VAS value of the skin state of the subject to whom the topical skin agent is applied at the measurement site on the side where the topical skin agent is applied. Therefore, the itching VAS value of "0" for the application amount differs depending on the type of topical skin agent. Table 2 shows the topical skin agents (1) to (4) to be applied. The application amount is the amount applied in one application.

[0027]

Table 2

[0028] FIG. 11(a) is a bar graph showing the evaluation results when the topical skin agent (1) is applied. Similarly, FIG. 11(b) is a bar graph showing the evaluation results of the topical skin agent (2), FIG. 11(c) is a bar graph showing the evaluation results of the topical skin agent (3), and FIG. 11(d) is a bar graph showing the evaluation results of the topical skin agent (4). The horizontal axis indicates the application amount of the topical skin agent, and the vertical axis indicates the itching VAS value (scale position (average value of 3 times)). Here, as shown in Table 2, since the topical skin agent (1) has an application amount of 8 μl per application, the application amount of 16 μl on the horizontal axis is after the second application, the application amount of 24 μl is after the third application, and the application amount of 32 μl is after the fourth application. Since the topical skin agents (2) to (4) have an application amount of 4 μl per application, the application amount of 8 μl on the horizontal axis is after the second application, the application amount of 12 μl is after the third application, and the application amount of 16 μl is after the fourth application. Also, the application amount of 8 μl corresponds to an application density of about 1 mg / cm 2 and an application density of about 2 mg / cm is achieved by applying 16 μl. 2 The p-value is shown in each figure (* indicates p < 0.05, and ** indicates p < 0.01 (two-sided t-test)).

[0029] ​The following was found as the evaluation results from FIGS. 11(a) to (d). It was found that for any of the skin external preparations, the itching VAS value decreased when applied compared to the bare skin. For any of the skin external preparations, when applied at 1 mg / cm 2 it was found that the itching was significantly alleviated. For any of the skin external preparations, when applied at 2 mg / cm 2 or more, it was found that the itching VAS value became less than half compared to the case of the bare skin.

[0030] FIG. 12(a) is a scatter diagram of the application amount and the itching VAS value when the skin external preparation (1) is applied. Similarly, FIG. 12(b) is for the skin external preparation (2), FIG. 12(c) is for the skin external preparation (3), and FIG. 12(d) is a scatter diagram of the application amount and the itching VAS value of the skin external preparation (4). The horizontal axis indicates the application amount of the skin external preparation, and the vertical axis indicates the itching VAS value (scale position (average value of 3 times)). In each figure, the coefficient of determination (R 2 ) is shown. The following was found as the evaluation results from FIGS. 12(a) to (d). It was found that for any of the skin external preparations, there was a significant negative correlation between the application amount and the itching VAS value. In particular, for the water-soluble moisturizing component (86% glycerin) of the skin external preparation (2), it was found that as the application amount increased, the itching VAS value decreased rapidly.

[0031] FIG. 13(a) is a graph for each subject of the application amount and the itching VAS value when the skin external preparation (1) is applied. Similarly, FIG. 13(b) is for the skin external preparation (2), FIG. 13(c) is for the skin external preparation (3), and FIG. 13(d) is a graph for each subject of the application amount and the itching VAS value of the skin external preparation (4). The horizontal axis indicates the application amount of the skin external preparation, and the vertical axis indicates the itching VAS value (scale position (average value of 3 times)). The following was found as the evaluation results from FIGS. 13(a) to (d). Although the absolute value of the itching evaluation differed depending on the subject, it was found that for any of the skin external preparations, the tendency and the range of decrease in the itching VAS value according to the application amount showed little difference among the subjects.

[0032] <Modification Example> In this embodiment, the tip of the fiber 11 that contacts the subject's skin is configured to move only in the direction perpendicular to the skin, but it is not limited to this. For example, the fiber 11 may move or contact the subject's skin at an angle other than the perpendicular direction, or the tip of the fiber 11 may be moved along the surface of the subject's skin. When contacting in this way, it is easy to evaluate the itching at a movement similar to when hair or clothing fibers contact the skin in daily life.

[0033] In this embodiment, the fiber 11 that contacts the skin is a single one, but a plurality of fibers 11 may be simultaneously brought into contact with the subject's skin. In this case, it is easy to simulate the itching when fibers such as clothing contact the skin in daily life. Also, although the fiber 11 is a single fiber (monofilament), it may be a fiber (multifilament) composed of a plurality of fibers. In this embodiment, for the fiber 11, the minimum load in the major axis direction required for bending is 4.9×10 -5 [N] to 1.2×10 -2 [N], but the range of the minimum load may be shifted to the larger side. The main point is that a predetermined load can be applied to the fiber in the major axis direction with the tip of the fiber in contact with the skin.

[0034] In this embodiment, the tip of the fiber 11 is brought into contact with the subject's skin at a speed of 1.6 [cm / sec] to 2.5 [cm / sec], but it is not limited to this. For example, it may be brought into contact from a position about 1 to 1.5 cm away from the subject's skin over 1 to 1.5 seconds. That is, it may be brought into contact at a speed of 0.7 [cm / sec] to 1.5 [cm / sec]. Similarly, the tip of the fiber 11 that has contacted the skin may be separated from the skin at a speed of 0.7 [cm / sec] to 1.5 [cm / sec].

[0035] In Evaluation Case 2 of this embodiment, the tip of the fiber 11 is vertically brought into contact with the measurement site from a position 2.5 cm away from the skin over 1 to 1.5 seconds, a load is applied over 1 to 1.5 seconds until the fiber 11 bends, and the load is removed over 1 to 1.5 seconds to eliminate the bending of the fiber 11. When this is done three times, although it does not mention at which position of the measurement site the tip of the fiber 11 is brought into contact, it is preferable to shift it slightly each time within the measurement site. Shifting the position where the tip of the fiber 11 is brought into contact in this way is closer to the actual state when hair or a fiber actually comes into contact, so it is easier to evaluate an itch closer to the actual itchy sensation.

[0036] In this embodiment, when quantifying the itch that the subject feels on the skin, it is not limited to five levels. Also, when quantifying using a scale, although the VAS method is used, it is not limited to this. It may be quantified (scored) using an itch questionnaire composed of questions regarding the change in itch over time and the intensity of the itch, and scored by the questions.

[0037] In this embodiment, the limb position of the subject during measurement is not particularly limited, but a comfortable posture and limb position are preferable. Also, the subject may lie on their back so that the evaluator can easily lower (come into contact with) the fiber 11 vertically onto the skin of the subject's face.

Explanation of Reference Numerals

[0038] 10 Itch evaluation instrument 11 Fiber 12 Support member 13 Fiber number

Claims

1. A contact step of applying a load to and bringing the tip of a fiber into contact with the skin of a subject, An acquisition step of acquiring the presence or absence or degree of itching that the subject feels on the skin in the contact step, An evaluation step of evaluating the itching felt on the skin using the acquisition result of the acquisition step, including, The contact step is bringing the tip of the fiber into contact with a predetermined position on the skin at a speed of 1.6 [cm / sec] to 2.5 [cm / sec], applying a load without moving from the predetermined position, applying a load so that the tip of the fiber in contact with the predetermined position on the skin bends 60° to 90° in the longitudinal direction of the fiber, removing the load so that the bent fiber remains in a non-bent state while in contact with the predetermined position on the skin, and separating the tip of the fiber in contact with the skin from the skin at a speed of 1.6 [cm / sec] to 2.5 [cm / sec]. A method for evaluating itching, characterized by this.

2. The method for evaluating itching according to claim 1, characterized in that the skin is the skin around the jaw or mouth.

3. In the acquisition step, the method for evaluating itching according to claim 1 or 2, characterized in that information quantifying the itching that the subject feels on the skin is acquired.

4. The contact step is a first contact step of bringing the tip of the fiber into contact in a state where the skin is in its natural state, and a second contact step of bringing the tip of the fiber into contact in a state where a topical skin agent is applied to the skin, and includes The acquisition step is a first acquisition step of acquiring the presence or absence or degree of itching that the subject feels on the skin in the contact state by the first contact step, and a second acquisition step of acquiring the presence or absence or degree of itching that the subject feels on the skin in the contact state by the second contact step, and includes The evaluation step evaluates the itching felt on the skin using the acquisition result of the first acquisition step and the acquisition result of the second acquisition step. The itching evaluation method according to any one of claims 1 to 3, characterized in that.

5. The fiber is one. The itching evaluation method according to any one of claims 1 to 4, characterized in that.

6. In the contact step, with the tip of the fiber in contact with the skin, 4.9×10 －５ [N] to 1.2×10 －２ A load of [N] is applied. The itching evaluation method according to any one of claims 1 to 5, characterized in that.

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