Cosmetic creams with caprylic acid-based Natural Eutectic Solvents: Stability, rheology and user perception.

Summary

Four caprylic/medium-chain-based hydrophobic NES at 10 wt% were integrated into an O/W cream. Three remained physically stable under 30-day accelerated aging, while a menthol-based NES caused phase separation with larger droplets and higher TSI. All creams were shear-thinning, and NES composition significantly modulated viscosity/yield stress and sensory attributes (odor, spread, pick-up, firmness).

Key Findings

• Three of four NES-containing creams remained physically stable over 30 days of accelerated aging; menthol-based NES induced phase separation with larger droplet size and higher Turbiscan Stability Index.
• All formulations exhibited shear-thinning behavior; viscosity profiles and yield stress depended on NES composition.
• Sensory attributes (odor intensity, spreading, pick-up, firmness) were significantly altered by NES type.

Clinical Implications

Guides formulators toward eco-friendly NES selection to achieve desired feel and stability, with caution for menthol-based NES that destabilize emulsions. Supports development of greener topical vehicles potentially relevant to dermatologic products.

Limitations

• Short evaluation window (30 days) and fixed 10% NES loading; no dermal safety or clinical performance data
• Limited to four NES systems; generalizability across actives and emulsifier systems untested

Future Directions

Extend stability to real-time/long-term studies, map NES concentration-response, evaluate skin compatibility and active delivery, and test across emulsifier systems and consumer cohorts.