Formulation and evaluation of topical essential oil lotion as repellent against Aedes aegypti

Mosquito-borne diseases, particularly dengue transmitted by Aedes aegypti, remain a major public health challenge, underscoring the urgent need for safe and effective plant-based repellents. We developed and evaluated a new lotion containing 15% w/w of a blend of citronella, patchouli, and sage essential oils, focusing on both skin safety and repellent efficacy. Skin compatibility was confirmed in 16 volunteers via patch testing at 30 min, 48 h, and 96 h post-application, with no irritation or allergic reactions observed. Repellent activity was assessed using the WHO-recommended Arm-in-Cage (AIC) method. The lotion achieved a mean complete protection time (CPT) of 103.13 ± 5.46 min and maintained > 90% protection over 3 h, with repellency rates of 100.0%, 99.41%, 94.19%, and 91.01% at 0, 1, 2, and 3 h, respectively. Across all volunteers, the mean repellency was 96.17 ± 0.81%, while biting rates remained below 14% at 3 h. These findings indicate that the essential-oil blend provides safe, sustained, and effective protection, supporting its potential as a natural alternative to synthetic repellents for personal protection against Ae. aegypti.