Essential oils-based nanoemulsion formulation boosts hair growth in C57BL/6 mice as compared to minoxidil 2%

Abstract

Developing effective and safe natural formulations to promote hair growth presents a significant opportunity in cosmetic and pharmaceutical sciences. This study aimed to formulate and evaluate a nanoemulsion containing a blend of lavender, peppermint, and rosemary essential oils (LPR) for enhanced hair growth, comparing its efficacy to 2% topical minoxidil. The LPR nanoemulsion, prepared using high-energy ultrasonic bath method, was optimized using varying surfactant-to-oil ratios (SORs) and characterized for droplet size, stability, and antioxidant activity via DPPH assay. Ex vivo skin permeation was tested using Franz diffusion cells . In vivo hair growth promotion was assessed in C57BL/6 mice (n = 15) over 4 weeks, with 2% topical minoxidil as a positive control and untreated mice as negative controls. Hair recovery was scored weekly, and histological analysis evaluated follicle count, depth, and mast cell activity using both hematoxylin and eosin (H&E) and toluidine blue stains. The optimized nanoemulsion (EM-5, SOR 5:1) exhibited a small droplet size (10.63 ± 0.05 nm), size stability over 60 days, and mild antioxidant activity (IC 50 34.20 ± 3.41%). Ex vivo permeation across rat skin demonstrated a sustained release profile, with 85.80 ± 9.79% of the LPR blend permeated over 24 h. In vivo, EM-5 promoted hair growth in C57Bl/6 mice. After 14 days of treatment, EM-5 and 2% topical minoxidil demonstrated a significant hair recovery percentage (HR%) compared to the negative control; HR% 73.33 ± 15.27; p = 0.0016, and HR% 76.66 ± 23.09; p = 0.0007), respectively, achieving full dorsal coverage by day 21. Histology revealed significantly increased follicle count/depth by both EM-5 and 2% topical minoxidil after 30 days of treatment. The LPR nanoemulsion EM-5 demonstrated favorable physicochemical characteristics, efficient skin permeation, and hair growth promotion comparable to 2% topical minoxidil. It represents a promising natural alternative for enhancing hair growth, likely due to the synergistic antioxidant and anti-inflammatory effects of its constituent essential oils.