Rheology of Cosmetic Products: Surfactant Mesophases, Foams and Emulsions.

Cosmetic products such as shampoos, body washes, mascaras, and foundations can all be classified essentially as complex fluids. Depending on the product format, the specific complex fluid used in a formulation can range from self-assembled surfactant systems found in most cleansing products to oil-in-water and water-in-oil emulsions found in makeup, color cosmetics, and skin care. These complex fluids play a critical role in giving rise to rheological and tribological properties necessary for both sensory and functional performance. Critical functional properties such as product stability and wet hair conditioning are impacted significantly through any changes in the product rheology. Positive sensorial properties of products are always desired by consumers, and as such, it is critical to always consider how to optimize formulation rheology to adequately deliver desirable sensory performance and properties. This review will focus on the importance of understanding and characterizing the rheology of complex fluids used in cosmetic products. A review and analysis of the recent literature in this area is presented.