UVA protection efficacy of sunscreens can be determined by the persistent pigment darkening (PPD) method (Part 2)

Background: The UVA-induced Persistent Pigment Darkening (PPD) in vivo has been proposed as an end point for the evaluation of UVA protection. Aims: This study was designed to determine whether PPD can be used to correctly evaluate the in vivo effectiveness of UVA filters such as oxybenzone, avobenzone, ecamsule and zinc oxide concentrated and together with UVB filters. Methods: The UVA protection effectiveness of a number of commercial sunscreen products with either SPF 15 or SPF 30 was determined. Results: The UVA protection increased closely with the concentration of the UVA filters and was independent of UVB filters. The PPD method proved sensitive to all UVA filters irrespective of their range of absorbance within the UVA range. Conclusion: The results show PPD to be a stable end point inducible by all the UVA wavelengths, not affected by fluence rate, i.e. a reliable endogenous UVA dosimeter in the skin.