Sun Protection Sample PFA Test

Cosmetics have become an essential part of people's daily lives because they not only cleanse and maintain the skin, but also improve the appearance of the skin, correct body odor, and keep people in good condition. CD Formulation provides customers with evaluation and support for long-wave UV protection index of sunscreen products, and moreover, we have one-to-one customized solutions to meet customers' differentiated needs.

What is PFA?

PFA (Protection Factor of UVA) refers to the ability to defend against UVA. Human testing is often used to test the PFA value of sunscreen cosmetics, and physical & chemical microbiological tests, toxicological tests, and human patch tests of sunscreen cosmetics should be completed and written reports issued before testing. For physical and chemical microbiological testing, toxicology tests, human patch test results do not meet the requirements of sunscreen cosmetics should not be tested for long-wave UV protection index.

PFA = MPPD (Minimal persistent pigment darkening dose) value of the skin coated with sunscreen / MPPD value of the skin not coated with sunscreen.

The arithmetic mean of the PFA value of the sample protection of all subjects is calculated, and the integer part of it is the PFA value of the measured sample. The sampling error of the estimated mean can be calculated as the standard deviation and standard error of the group data. The standard error should be less than 10% of the mean. Increasing the number of subjects can reduce the standard error value, but the maximum number of subjects should not exceed 20.

PFA Test Procedure

  • After the subjects are selected and meet the entry criteria, they are irradiated with a sunlight simulator for 5 minutes to test the MPPD values.
  • Take part in the product test at the scheduled time, which takes about 2 hours.
  • View the test results again and the test is completed.

Preparation of PFA Value Standards

For better quality control of the testing process and to ensure the validity and consistency of the test results, the PFA value of the sunscreen product should be measured at the same time as the PFA value of the standard product. When the PFA value of sunscreen cosmetics is <12, the low PFA value standard can be selected; when the PFA value of sunscreen cosmetics is ≥12, the high PFA value standard can be selected. The high PFA value standard can be used for any product test, and only one standard formula needs to be referred to for each test.

In the PFA value test report, the theoretical PFA value of the standard used should be written, and the PFA value measurement results of the test object and the standard should be listed separately.

Determination of the MPPD

In the determination of the minimal persistent pigment darkening dose, the subject may be placed in a prone or forward position with the light source irradiated on the posterior part of the back.

The sample is weighed at a dosage of (2.00 ± 0.05) mg/cm2. The sample should be applied in the same way as it is actually used, and the sample should be applied accurately and evenly on the skin of the subject area. The sample application area should not be less than 30 cm2, e.g. when the application area is 30 cm2, the total amount of sample used should be in the range of 58.5-61.5 mg. It is recommended that the sample be applied evenly to the test area using a latex fingertip (for more viscous products and powdered products that are difficult to apply evenly using a latex fingertip, you can apply the sample directly with your finger and wash your finger before each application). After applying the sample, wait for 15-30 min.

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