Sun Protection Factors in Evaluation of Sunscreen Potency: The Persistent Pigment Darkening Method

Sun Protection Factors in Evaluation of Sunscreen Potency: The Persistent Pigment Darkening Method

The Persistent Pigment Darkening (PPD) method has been modified by Bissonette et al. as an in vivo assay for UVA exposure. This is the gold standard with which to compare many other methods that assay the potency of sunscreens that block UVA damage. In view of the current interest in evaluation of sun protection factors (SPF), it is important to ensure the validity of current methodology used to evaluate UVB and UVA exposure before meaningful evaluation of sun protection factors and potency of sunscreens against UVinduced damage can be made.