Transparent Surfactant‐Based Isotropic Systems for Topical Co‐Delivery of Hydrophilic and Lipophilic Actives for Striae Distensae

ABSTRACT Striae distensae are common dermal lesions that negatively affect skin appearance, and topical management remains limited by challenges related to skin deposition and residence time. Here, we developed transparent surfactant‐based isotropic systems for the topical co‐delivery of ascorbic acid (AA), retinoic acid (RA), and lavender essential oil (LEO) as a multifunctional system for striae distensae management. Ternary phase‐diagram screening identified transparent single‐phase regions, and polarized light microscopy, pH, thermal profiling, texture profile analysis, and rheology were used to characterize three shortlisted formulations (ME28, ME29, and ME32). ME28 showed the most favorable mechanical profile, combining high adhesiveness and hardness with shear‐thinning behavior that supports skin residence while maintaining spreadability. Phase‐continuity studies (dye diffusion, low conductivity, and selective dilution) indicated an oil‐continuous (W/O‐like) structured isotropic system. Upon 1:100 aqueous dilution, ME28 formed a visually transparent dispersion with a hydrodynamic diameter of ~359 nm, PDI ~0.25, and zeta potential of −22 mV. ME28 also maintained macroscopic homogeneity, resisted centrifugation, and preserved an isotropic pattern under polarized light microscopy over 90 days, with better visual preservation under refrigeration. Preliminary cytocompatibility testing showed high fibroblast viability up to 0.25 mg/mL. Overall, ME28 represents a promising structured isotropic system for topical co‐delivery, combining mechanical performance, physical stability, defined phase‐continuity behavior, and preliminary cytocompatibility.