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In vivo persistent pigment darkening method: proposal of a new standard product for UVA protection factor determination

The European Commission (EC) has recommended assessing the level of ultraviolet A (UVA) protection afforded by sunscreen products using the in vivo persistent pigment darkening (PPD) method or other methods giving equivalent results. In this context, the reproducibility of the in vivo PPD method is of importance. To check the validity of the UVA protection factor (UVAPF) tests, the Japanese Cosmetic Industry Association (JCIA) recommends using a standard product (JCIA standard) with an expected UVAPF 3.75 (SD 1.01). However, considering the increase in UVA efficacy of the new sunscreen products available in the market, with UVAPF up to 30, it seemed useful to develop a new standard product to be used when testing products with expected UVAPF ≥10. The PPD method was used in six centres to determine the UVAPF of the two products. Reproducibility of results was also studied by testing two batches of the new product at two different times. There was no statistical difference between the six centres with regard to the JCIA standard. The ring study showed that the mean value of UVAPF (4.3) was higher than that given by JCIA (3.75). These data enable the proposal of a new acceptance range for the JCIA standard product (3.4–5.2) derived from actual results from European laboratories. Whereas this range is different from that proposed by JCIA (2.74–4.76), there is an overlapping of the values. Data on the new standard product show that reproducibility is not influenced by the batches of this product. The mean UVAPF value obtained is 12.1. An acceptance range (9.6–14.6) is proposed for the new standard. Data presented here demonstrate that if an identical protocol is used, reproducible results can be expected and that the PPD method is reproducible and reliable.