Formulation and Evaluation of Black Seed Oil and Calendula Oil Microemulsions using Vegetable oil Ethoxylates for Itch Relief Spray Application

The aim of this study was to develop and assess microemulsion-based itch relief sprays containing Black Seed Oil (Nigella sativa) and Calendula Oil (Calendula officinalis) using vegetable oil ethoxylates as green surfactants. Both oils were selected due to their established potential to act as anti-inflammatory and soothing (Calendula Oil) and antimicrobial (Black Seed Oil) complementary agents in pruritus management. Physicochemical characterization was performed to confirm pure oils and stable formulation. Pseudo-ternary phase diagrams identified broad microemulsion regions exhibiting potential for stable formulation. Optimized formulations showed desired physicochemical characteristics, including droplet size <215 nm, acceptable pH of 6.4–6.8, and homogeneous appearance showing no phase separation under centrifugation or 30 day accelerated stability testing. Increased sensory properties of the formulations were noted upon the incorporation of humectants and naturally derived additives providing a non-greasy, fast absorbing, and soothing user experience. The developed microemulsion-based spray was stable after 30 days at room temperature and 40°C conditions with no change to the visual clarity or viscosity. This study provides a biocompatible, natural, and stable microemulsion vehicle delivered two synergistic botanical oils for successful itch relief and further dermocosmetic vehicle utilization.