Short-term Moisturizing Efficacy Test

The moisturizing efficacy test of cosmetics is applicable to skin care cosmetics (such as skin creams, lotions, gels, etc.) that claim "moisturizing" efficacy. The short-term skin moisturizing efficacy test is used to evaluate the moisturizing effect of the product in a short period of time after use, focusing on testing the moisturizing duration of the product on the skin surface. Skin care creams, lotions and gel cosmetics are often selected for this test.

What is Moisturizing?

The amount of moisture in the skin directly affects the skin's appearance. Skin with low moisture levels tends to be dry, tight, and flaky. To a certain extent, cosmetics can replenish the skin and slow down the loss of water. This process is commonly known as moisturizing.

How to Test for Short-term Moisturizing Efficacy?

For the short-term moisturizing efficacy test, the inner arm skin of the subject was selected as the test area, because the inner forearm skin is relatively flat and easy to test, and is not easily disturbed by the external environment.

During the evaluation process, several test time points will be set, and the moisture content of the skin stratum corneum will be determined in the area where the test sample is applied and in the comparison area.

The time points for short-term moisturizing efficacy tests are usually 0,1, 3, 6 h or 0, 2, 4, 8 h, that is, 0 h before using the product, 1, 3, 6 h or 2, 4, 8 h after using the product, the moisture content of the skin stratum corneum of the subjects was collected at these 4 time points. In addition, more measurement points can also be changed and set according to product evaluation requirements, but usually the total duration will not exceed 24 hours.

Short-term Moisturizing Efficacy Test Process

1. The test personnel in the laboratory uniformly cleaned the inner sides of the forearms of both hands. Subjects sat quietly for at least 20 min in a laboratory with a temperature of 21±1℃ and 50±5%RH. During this period, they could not drink water and beverages, and their forearms were exposed and kept relaxed.
2. Select and mark 2 areas on the inside of both arms, each with an area of 3 cm×3 cm.
3. Test the basic value of the water content of the stratum corneum in each area of the forearm of the test subject.
4. Mark the product area and control area, and use test samples in the product area according to product use requirements.
5. After 1 h, 3 h, 6 h, test the moisture content of the stratum corneum in each area of the forearm of the subject.

Laboratory Test Principle

The moisture content test of the skin stratum corneum is based on the principle of capacitance method.

The dielectric constant of water (81) is generally greater than that of other substances (generally <7), so the dielectric properties of the outer surface of the skin change with the change of moisture content, and the precision capacitor on the probe can accurately measure the change of permittivity, thus reflecting the skin Moisture content of the superficial stratum corneum. Unlike the impedance method, no current is generated between the device and the object to be measured, and there is no polarization effect.

Our Advantage

CD Formulation can provide you with the short-term moisturizing efficacy test for cosmetics. And the laboratory uses an advanced instrument to test the short-term moisturizing efficacy of cosmetics.

The instrument has the following characteristics:

• Less susceptible to skin surface chemicals and salts.
• The measurement depth is the stratum corneum (10-20 μm), effectively excluding the influence from the deep skin (such as the influence from blood vessels).
• The test probe is small in size and easy to use, and can test any part of the skin (such as lips).
• The probe spring provides constant pressure, high precision (measurement uncertainty ±3%), and good repeatability.
• Continuous measurement over a long period of time can be realized.
• Rapid measurement, convenient calibration, no blockage.
• The probe is easy to clean, reducing system errors caused by contamination.

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Reference

1. Guidelines to Commission Regulation (EU) No 655/2013.