Carrier for skin actives

Szymula investigated the impact of Vitamin C on the flow properties of microemul-sions [31]. Microemulsions based on sodium dodecylsulphate, pentanol and water were evaluated. They exhibit Newtonian flow behaviour for o/w and w/o systems, while the bicontinuous phase is shear thinning. The addition of ascorbic acid leads to an increase in viscosity. 

There is a large consumer demand for skin moisturisation in day care products. Skin care compositions, which contain a skin moisturiser in combination with a humectant, are found to be very effective in microemulsion formulations based on non-ionic surfactant in combination with siloxanes and organic oil [34]. 

Aluminium chlorohydrate is a widely used active ingredient for antiperspirant compositions. This salt requires a hydrophilic solvent at low pH values to remain stable. Structured microemulsions can be used to formulate clear and viscous products with this active. These products can be used in solid applicators such as firm stick applicators [35]. The o/w microemulsions can be based on fatty alcoholethoxylates with an organic or silicon oil phase [36]. An improved temperature stability in the range of 0-70°C for such formulations can be achieved by a combination of oxyalkylene-modified siloxanes, pentacyclosiloxane and glycol [37]. The addition of alpha-hydroxylic acids results in an improved skin feel with decreased tackiness [38]. 

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