Percutaneous permeability of 1-phenoxy-2-propanol, a preservative in cosmetics

1-Phenoxy-2-propanol (PP) is used as a preservative in cosmetics. PP is currently permitted to be used to up to 1% in cosmetic formulations in Korea and Europe. For risk assessment, percutaneous absorption is a crucial factor, but dermal absorption of PP has not yet been reported. In this study, Franz diffusion method was used to determine the percutaneous penetration of PP using the dorsal skin of rats. Each formulation of shampoo or cream, 113.6 mg/cm², was applied to a donor compartment of Franz diffusion cell for 24 h. Receptor fluid was collected at 0, 1, 2, 4, 8, 12, and 24 h following dermal application. Remaining formulation was removed with a cotton swab after last sampling. Using tape stripping method, stratum corneum was removed. PP in epidermis and dermis was extracted in PBS for 24 h. The concentration of PP from the swab, stratum corneum, and epidermis and dermis samples was determined using high performance liquid chromatography. Total percutaneous absorption rates of PP for shampoo and cream were 50.0 ± 6.0% and 33.0 ± 3.2%, respectively. In vitro skin permeability was calculated as 1,377.2 ± 240.1 mg/cm² for shampoo and 1,038.0 ± 72.2 mg/cm² for cream for 24 h.