JP2010201138A - Device for evaluation of skin barrier function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply, as an inexpensive and compact device, a means for obtaining a skin barrier function by water evaporation in skin without being affected by an air flow in the circumference of a measurement probe. <P>SOLUTION: A humidity sensor-incorporating compact capsule, where only a skin adhesion side is opened, is filled with dry air, at first, before adhering onto the skin. An air filling method is the method for inserting the capsule part of the probe to a low-humidity container with a drying agent such as silica gel put therein before measurement or the method for supplying the air of the drying agent container to the capsule with the use of some kind of blowing means. Consequently, the change of an evaporation amount from the fixed low humidity is obtained after adhesion onto the skin. Thus, the skin barrier function is evaluated by the model of water diffusion from the skin to the sealed capsule. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for evaluating a skin barrier function in a short time based on the amount of water evaporated from human skin.

  Moisture transpiration from the skin is used as an index representing the barrier function of the skin as an evaluation of the efficacy of skin care cosmetics and as an evaluation of colonization and recovery after skin transplantation. As the measurement method, for example, as in JP-A-2002-263072, a small capsule may be brought into close contact with the skin and the internal humidity may be detected.

  However, moisture transpiration from living bodies depends on environmental humidity. For example, in a high humidity environment, the change in transpiration is small regardless of whether the skin barrier function is good or not. In order to evaluate the barrier function, it is first necessary to measure the amount of water transpiration when a constant humidity environment is brought into contact with the skin. Therefore, since the conventional moisture transpiration measuring device does not consider environmental humidity, it cannot be applied to the skin barrier function evaluation as it is.

  Methods have also been devised in which the amount of transpiration is determined by measuring humidity while supplying air into a capsule in close contact with the skin (Japanese Patent No. 3294528, Japanese Patent No. 3569215, and Japanese Patent No. 3559993). If this supply air is kept constant at low humidity, the barrier function may be evaluated. However, in this method, the upper surface of the capsule has to be released as a passage through which supply air is released, and it is easily affected by the surrounding airflow. Also, considering the necessity of maintaining the air supply during measurement, it is clear that it is difficult to reduce the size and cost in principle.

Challenges to be solved

  An inexpensive device that evaluates the skin barrier function with a simple operation.

Means for solving the problem

  In order to set a constant humidity environment at the measurement site of the skin, a closed space (capsule with the skin contact side released) is created. By prefilling the capsule with dry air at a constant humidity before measurement, skin transpiration always begins at approximately the same initial environmental humidity.

  Measure the humidity in the capsule over time when the capsule is in close contact with the skin, and determine the transpiration rate change assuming that the transpiration is simple diffusion due to the humidity difference between the living body and the external environment. The amount of transpiration with respect to environmental humidity is used as a barrier function index (barrier ability).

The invention's effect

  By taking the above measures, it is possible to measure skin moisture transpiration at a constant environmental humidity and evaluate skin barrier ability using inexpensive components such as capsules, small humidity sensors, and silica gel for dry air production. .

  Two methods are conceivable as means for simply carrying out the invention with inexpensive parts. One is a method in which a capsule containing a small humidity sensor is directly inserted into a silica gel container that produces dry air, the capsule is lowered to a certain humidity, and then brought into close contact with the skin.

  The other is to provide a passage through which dry air is fed into a capsule that also contains a small humidity sensor, and after the inside of the capsule has been lowered to a certain humidity, the passage is closed and measurement is started by bringing it into close contact with the skin.

  After the capsule is brought into close contact with the skin by one of the above two methods, the humidity increase in the capsule is measured by a small humidity sensor attached to the inside, and the amount of moisture transpiration is calculated from the rising curve.

  FIG. 1 shows the first method. In this method, the tip of the probe A is inserted into a low-humidity container B containing silica gel before measurement, and the humidity of the capsule 5 containing the temperature / humidity sensor 4 is lowered.

  The movable cylinder 6 is pushed out by the coil spring 3 except when the probe A is pressed against the skin. This temporarily doubles the capsule volume in order to prevent the humidity in the capsule from rapidly returning to the external environmental humidity when the probe is taken out from the low-humidity container B.

  FIG. 2 shows the second method. In this method, air is sent to the silica gel cartridge 10 by the blowing rubber ball 11 immediately before measurement, and dry air is sent to the capsule 5 via the one-way air valve 9. A one-way air valve may be a solenoid valve, but a rubber duckbill valve (a rubber valve that opens only when air pressure is applied) is sufficient to achieve low cost. The amount of transpiration can be measured by bringing it into close contact with the skin after blowing. The blowing method in this method is not limited to the rubber ball, but may be a piston-cylinder method such as a syringe, or a method using a small electric air pump.

  In both the first method and the second method, the humidity of the dry air produced by the silica gel is limited, so that the humidity in the capsule rises from almost the same level every time. If the humidity does not drop to a pre-determined value, the signal processing times are designed to issue a warning to replace the silica gel.

  In both the first and second methods, the capsule is designed to be small in order to speed up the response as much as possible. For this reason, the distance from the skin is shortened, and the temperature in the capsule gradually increases depending on the body temperature. Therefore, in the case of a sensor that obtains relative humidity, the temperature is measured simultaneously and corrected with the saturated water vapor pressure to measure absolute humidity.

The method for evaluating the skin barrier ability from the change over time in the capsule humidity obtained by the first or second method is as follows.
First, assuming that the humidity in the capsule is an amount x (t) depending on the time t and the virtual humidity on the skin side is W (≈100%), transpiration occurs as diffusion due to this difference, and is expressed by the following equation.
K · dx (t) / dt + x (t) = W (1)
Where K is a diffusion coefficient,
K = V · L / (P · A) (2)
V: Capsule volume, A: Measurement area, L: Diffusion distance, P: Permeability coefficient of skin. L is equivalent to the thickness of the skin, but cannot be measured.
B = L / P (3)
With skin barrier ability.
Solving equation (1), x (t) = (X0−W) · exp (−t / K) + W (4)
X0: The initial humidity of the capsule. X0, K, and W are obtained by measuring the time-dependent change x (t) of the humidity in the capsule and extrapolating the equation (4) by the least square method. The skin barrier ability is determined from the value of K using equations (2) and (3).

  An actual measurement example is shown in FIG. 3 (a) and 3 (b) are cheek measurements, (a) is a healthy part and (b) is a part with rough skin compared to (a). When these curves are fitted to the above equation (4) by the method of least squares, extrapolation can be performed with a correlation coefficient of 0.99, and the coefficients at that time are as shown in the table. From this, each barrier ability B (formula (3)) of (a) and (b) is evaluated as 17.5 and 11.2.

Skin barrier ability evaluation probe and dry air filling method before measurement (first method) Skin barrier ability evaluation probe and dry air filling method before measurement (second method) Actual measurement example-(a) Example with high skin barrier function, (b) Example with low skin barrier function

DESCRIPTION OF SYMBOLS 1 Display 2 Signal processing circuit 3 Coil spring 4 Temperature / humidity sensor 5 Capsule which released skin contact side 6 Moving cylinder 7 Rotating lid 8 Silica gel 9 One-way air valve 10 Silica gel cartridge 11 Blow rubber ball A Skin barrier function evaluation probe B Low Humidity container C Arrow indicating air flow

Claims (3)

  An apparatus for evaluating a skin barrier function by placing a temperature / humidity sensor in a capsule to be brought into contact with the skin and filling the capsule with dry air, and contacting the skin with a substantially constant low humidity environment each time. .   An apparatus characterized in that the absolute humidity change with time in a capsule is obtained by temperature correction, and the data on the absolute humidity change is applied to a theoretical formula using moisture diffusion from the skin to the capsule as a model to obtain skin barrier ability.   A skin barrier function evaluation device that gives a warning with a display or sound to replace a desiccant such as silica gel if the inside of the capsule cannot be lowered to a predetermined humidity before the start of measurement.