In Vitro Whitening Test

Cosmetic whitening efficacy assessment is to evaluate the whitening effect by controlling the color and melanin value of the skin at various points in time before and after the use of the test samples by the subjects, usually in the form of half-face control or group control, applicable to cosmetics claiming whitening efficacy.

Test Sites

Cheeks are generally chosen as the test site for whitening efficacy evaluation tests because most whitening cosmetics are applied to the face. However, since the face is easily exposed to direct sunlight, which can interfere with the evaluation, the test date should be chosen to avoid periods of intense and prolonged sunlight, with winter being the most suitable of the four seasons. If the test time period is chosen to be affected by strong sunlight, sunscreen products can be used in conjunction with the assessment process, or the inner forearm skin can be chosen as the test site to minimize the influence of light.

Evaluation Period

The test cycle for whitening efficacy evaluation takes at least 28 days, and may be extended depending on the effectiveness of different products and actual needs. The human skin's stratum corneum renewal cycle is usually 28 days, so if the test cycle is too short, it will not be able to obtain accurate data on the effects of use. Taking the 28-day test cycle as an example, subjects need to go to the laboratory for whitening efficacy testing at three points in time: before using the test sample, two weeks after using the test sample, and four weeks after using the sample.

In Vitro Whitening Test Program

Cosmetic whitening efficacy evaluation methods mainly include in vitro enzyme inhibition, cell biology, animal experimentation and human testing, of which the human testing method can most directly and objectively reflect the effect of cosmetic use. Cosmetic whitening human efficacy evaluation test can be divided into subjective assessment and objective measurement and statistical analysis of two, subjective assessment method is divided into visual assessment and volunteer self-assessment.

• Melanin content measurement

Most of the whitening cosmetics sold in the market achieve whitening effect by inhibiting, blocking or influencing melanin production and transportation, so melanin content measurement on the skin is a common test method to evaluate the whitening efficacy of cosmetics.

The Skin Melanin and Hemoglobin Tester is an instrument that measures the melanin content of the skin. The spring in the probe keeps the pressure constant during each test, ensuring the repeatability and accuracy of the experimental data. Melanin level is characterized by the MI value and hemoglobin content by the EI value. The lower the measured value, the lower the melanin and hemoglobin content, i.e. the lighter the skin.

• Skin color measurement

The final effect of whitening cosmetics is a reduction in skin coloration. Therefore, by analyzing the changes in skin chroma before and after the use of whitening cosmetics, the whitening efficacy of the product can be verified.

• Face imaging acquisition

In addition to localized data acquisition of the cheeks, the whitening efficacy assessment also requires image acquisition of the subject's front face, left and right side faces, so as to obtain a more intuitive image of the skin color of the face and software-calculated skin color data for comparative use in the assessment. In the CD Formulation Cosmetic Efficacy Lab, we use a facial imager to acquire images of the face. The Facial Imager can be analyzed by the software to provide the values of spots, wrinkles, texture, pores, UV spots, brown spots, red zones, and purple texture, which are all indicators that directly affect skin color.