Formulation, Physicochemical Characterization, and Repellent Activity of a Topical Lotion Containing Ylang-Ylang (Cananga odorata) and Patchouli (Pogostemon cablin) Essential Oils Against Aedes aegypti

Abstract

Background: Aedes aegypti is a major vector of dengue, chikungunya, and Zika and remains a significant public health concern in tropical regions, including Indonesia. The increasing burden of mosquito-borne diseases underscores the need for effective, safe, and environmentally sustainable alternatives to synthetic repellents. Patchouli (Pogostemon cablin) and ylang-ylang (Cananga odorata) essential oils have demonstrated repellent activity and may serve as promising botanical ingredients for topical formulations.
Objective: To formulate a topical repellent lotion containing patchouli and ylang-ylang essential oils at a constant total concentration of 3% w/w with varying ratios, and to evaluate its physicochemical characteristics, physical stability, preliminary skin tolerability, and repellent activity against adult female A. aegypti.
Methods: Four oil-in-water formulations were prepared: F0 (oil-free base), F1 (patchouli:ylang-ylang, 1:2), F2 (1:1), and F3 (2:1). Organoleptic characteristics, homogeneity, pH, viscosity, spreadability, and 28-day physical stability were evaluated. Skin tolerability was assessed using a Human 4-Hour Patch Test in six volunteers. Repellent activity was evaluated using a modified arm-in-cage assay with 20 adult female A. aegypti per treatment.
Results: All formulations remained homogeneous without apparent organoleptic changes or phase separation during storage. pH, viscosity, and spreadability ranged from 6.97–6.99, 13,517–14,616 mPa·s, and 6.00–6.87 cm, respectively. No erythema or oedema was observed in any volunteer. Repellent protection was highest for F1 (100%; 20/20 mosquitoes), followed by F3 (95%; 19/20) and F2 (45%; 9/20), compared with 0% for the control. F1 and F3 significantly outperformed the control, whereas their difference was not statistically significant.
Conclusion: The patchouli–ylang-ylang combination produced a physically stable lotion with acceptable preliminary skin tolerability and substantial repellent activity. The results suggest that the essential-oil ratio may influence repellent performance beyond total concentration, with F1 (1:2) showing the highest observed protection. Further studies should evaluate protection duration, concentration–response relationships, and potential interactions between the essential oils.