Composition for the cosmetic and/or pharmaceutical treatment of the upper layers of the epidermis by topical application to the skin, and corresponding preparation process

A process for the treatment of the upper layers of the epidermis comprising topically applying to the skin in an amount effective to treat the upper layers of the epidermis a composition comprising in a vehicle suitable for topical application to the skin, biodegradable polymer nanoparticles having a size ranging from 10 to 1,000 nm and encapsulating an oily phase comprising one or more of at least one active ingredient in the form of an oil or at least one active ingredient contained in an inactive carrier oil or an active oil, said active ingredient having a cosmetic action or a pharmaceutical action or both beneath the stratum corneum, said nanoparticles loaded with said active ingredient being present in an amount ranging from 0.1 to 20 percent by weight based on the total weight of said composition.