According to the Standard for the Evaluation of Efficacy Claims of Cosmetics, cosmetics with repair efficacy (helps to maintain the application site in normal conditions) should be evaluated by means of a human efficacy evaluation test.
At present, China NMPA has not yet issued a unified evaluation method and standard for the repair efficacy. The main evaluation standards referenced by industry testing institutions and laboratories are: T/SHRH 006-2018 Cosmetics -Free Radical (DPPH) Scavenging Test Method and T/SHRH 023-2019 Skin barrier efficacy test of cosmetics - In vitro reconstructed human skin test method issued by Shanghai Daily Chemistry Trade Association, T/ZHCA 003-2018 Method for assessment of cosmetics on transepidermal water loss issued by Zhejiang Health Products & Cosmetics Industry Association, and T/GDCA 009-2022 Evaluation method for repairing efficacies of cosmetics issued by Guangdong Cosmetics Association.
The test design of repair efficacy evaluation mainly has the following dimensions: transepidermal water loss (TEWL), stratum corneum water test, lactic acid tingling test (LAST), skin erythema index (EI), skin oil test, and skin pH test.
This article mainly introduces transepidermal water loss (TEWL), lactic acid tingling test (LAST), and skin erythema index (EI).
Transepidermal water loss (TEWL)
This method verifies the repair efficacy of cosmetics based on testing the impact of the recovery process of transepidermal water loss in barrier-damaged skin.
Test instrument: Tewameter
Use samples twice a day for 28 days. Clinical testing and evaluation are performed at D0, D14, and D28, respectively. After 28 days of product use, the lower the TEWL value, the less of Transdermal water loss, and the better the barrier function of the skin Stratum corneum, that is, the better the repair efficacy.
Lactic acid tingling test (LAST)
This method is a semi-subjective evaluation method, and the mechanism is that when the skin barrier is damaged, lactic acid enters the skin and produces a tingling sensation.
Under a constant temperature and humidity environment, the lactic acid solution is applied to the subject area, and the subjects are asked about their self-perceived symptoms at 2.5 min and 5 min, respectively, and score (0 as no stinging sensation, 1 as mild stinging, 2 as moderate stinging, and 3 as severe stinging). The two scores are then summed, and those with a total score ≥3 are considered positive for lactic acid stinging response.
Use samples twice a day for 28 days. Testing and evaluation are performed at D0, D14, and D28, respectively. If the lactic acid tingling score is lower after 28 days of using the tested product, it indicates that the product has a repair efficacy.
Skin erythema index (EI)
The lower the erythema index (EI), the more effective the product is in repairing the skin and improving the skin's erythema reaction.
Test instrument: VISIA-CR
Use the sample twice a day for 28 days. Test and evaluate at D0, D14, and D28, respectively. If the skin's erythema index decreases after 28 days of using the test product, it indicates that the product has a repair efficacy.
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