Physicochemical Characterization and Safety Assessment of Cosmetic Gels and Emulsions Containing Sand-Extraction...

Clays are widely used in cosmetic formulations for their rheological properties, adsorption capacity, and potential skin benefits. Sustainable sourcing of clays from industrial by-products, such as sand extraction residues, is gaining interest in the cosmetics industry.

This study aimed to assess the feasibility of incorporating four clays (I, II, III, IV) derived from sand extraction residues into cosmetic gels and emulsions, evaluating their physicochemical properties, biocompatibility, and dermal safety.

The clays were incorporated into two types of hydrophilic vehicles (a nonionic emulsion and a gel). Formulations were characterized for particle size, viscosity, and storage stability over 90 days. Cytotoxicity was evaluated in vitro using HaCaT keratinocytes exposed to clay concentrations up to 1000 μg/mL. Dermal irritation potential was assessed in vivo on 53 healthy volunteers via patch testing.

Clay incorporation affected particle size and viscosity, with gels showing superior physical stability. All clays preserved HaCaT cell viability above 75% at the highest concentration, and in vivo assessments revealed no signs of skin irritation or sensitization. Clay III showed the largest surface area, improving skin adhesion and spreadability, while consistency between in vitro and in vivo data confirms the biocompatibility and cutaneous safety of the formulations.

Clays from sand extraction residues are safe, stable, and biocompatible ingredients for cosmetic formulations. Their incorporation into gels and emulsions provides favorable rheological and dermatological properties, supporting their potential as sustainable raw materials for cosmetic and dermatological applications.