Applied Cosmetic Science and Technology Applied Cosmetic Science and Technology

The stratum corneum (SC) acts as a barrier that regulates water loss from the body and prevents various external stimuli. Additionally, it retains water and maintains moisture in the body. These barrier and moisturizing functions deteriorate with age and in dry environmental conditions. In this study, we focused on petroleum (widely used as a moisturizer in creams and other products) as a novel approach to maintain the water retention capacity of the SC, aiming to develop ingredients that further enhance moisturization. Petroleum is a water-insoluble, long-chain hydrocarbon with very low skin permeability. Its moisturizing effect is exclusively achieved by covering the skin surface to prevent moisture loss. In contrast, it is easily eliminated from the skin surface via contact or rubbing, and its effects are short-lived. A newly developed petroleum nanoemulsion (nano-petroleum), achieved by reducing the particle size to approximately ≤80 nm, enhances penetration into the SC. Additionally, it was confirmed that the product had post-penetration moisture retention and swelling effects on the SC. The skin permeability of petroleum is considered to be extremely low; however, nanosizing enhances its texture by stably dissolving it in a water-based formulation, combining its moisture retention effect with enhanced skin permeability. We believe that this research has uncovered novel potential applications for petroleum, enabling its use in various cosmetic formulations.