How can you determine persistent pigment darkening in a spf of 100?

Persistent pigment darkening (PPD) can be assessed by conducting a standardized test, often involving the application of the SPF product to a designated area of skin. After exposure to UV radiation, the skin's pigmentation changes are measured at specific intervals, typically 24 to 48 hours later, to evaluate the degree of darkening. The results are compared to a control area that did not receive the SPF product. A higher degree of darkening indicates lower protection against pigmentation, even with a high SPF rating.