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

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 (IC50 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.