Herbal nanoemulsions in cosmetic science: A comprehensive review of design, preparation, formulation, and characterization.

The rapid development of delivery systems for cosmetics has revealed two critical challenges in the field: enhancing the solubility of active ingredients and ensuring the stability of natural materials used in cosmetics. Nanoemulsion technology has emerged as an indispensable solution for addressing these challenges, not only enhancing the stability of cosmetics but also improving the solubility of pharmaceuticals and active ingredients with poor solubility. Nanoemulsion formulations have reinforced stability and amended the bioavailability of hydrophobic drugs. Moreover, nanoemulsion exhibit excellent skin penetration and long-lasting effects, making them particularly appealing to consumers, especially in the cosmetic industry. This article aims to provide an overview of herbal nanoemulsion formulations as cosmetic products, covering formulation, production, and characterization. Herbal nanoemulsions is an effective, stable, and promising option for cosmetic delivery. The nanoemulsions were characterized by their key properties, such as particle size, polydisperse index (PDI), zeta potential, viscosity, stability and others. Techniques like zeta potential measurement, transmission electron microscopy (TEM) and scanning electronmicroscopy (SEM) were used to analyze the surface morphology, whereas stability tests were employed to evaluate nanoemulsion performance. This review also delves into the high-energy and the low-energy methods of manufacturing nanoemulsions. Additionally, we also explore the selection of appropriate surfactants, co-surfactants, and ingredients for creating herbal nanoemulsions with desirable attributes and qualities. Overall, this review consolidates the current knowledge on herbal nanoemulsion formulations for cosmetic preparations, designs, shedding light on their effectiveness, characteristics, and stability. These formulations hold promise in overcoming challenges related to meeting the increasing demand for effective herbal nanoemulsion and high-quality cosmetic products.