Unconventional and conventional Pickering emulsions: Perspectives and challenges in skin applications

Pickering emulsions are free from molecular and classical surfactants and are stabilized by solid particles, creating long-term stability against emulsion coalescence. Additionally, these emulsions are both environmen-tally and skin-friendly, creating new and unexplored sensorial perceptions. Although the literature mostly de-scribes conventional emulsions (oil-in-water), there are unconventional emulsions (multiple, oil-in-oil and water -in-water) with excellent prospects and challenges in skin application as oil-free systems, permeation enhancers and topical drug delivery agents, with various possibilities in pharmaceutical and cosmetic products. However, up to now, these conventional and unconventional Pickering emulsions are not yet available as commercial products. This review brings to the discussion some important aspects such as the use of phases, particles, rheological and sensorial perception, as well as current trends in the development of these emulsions.

Automated summary

Pickering emulsions, stabilized by solid particles instead of molecular or classical surfactants, provide long-term stability against emulsion coalescence. They are environmentally and skin-friendly, offering new sensorial experiences. Besides conventional oil-in-water emulsions, unconventional multiple, oil-in-oil, and water-in-water emulsions have great potential for various applications in pharmaceutical and cosmetic products, such as oil-free systems, permeation enhancers, and topical drug delivery agents. However, despite their potential, commercial products of these Pickering emulsions are not yet available. This review discusses important aspects such as phase behavior, particle properties, rheology, sensorial perception, and current development trends of these emulsions.