Tehran University of Medical Sciences Journal of Arthropod-Borne Diseases 2322-1984 20 2 2026 08 15 1968 1968 Faranak Firoozfar Department of Vector Biology and Control of Diseases, School of Public Health, Tehran University of Medical Sciences (TUMS), Iran, Students Scientific Research Center, Tehran University of Medical Sciences (TUMS), Tehran, Iran, Department of Public Health, Faculty of Health, North Khorasan University of Medical Sciences (NKUMS), Bojnurd, Iran Mahboubeh Fatemi Department of Vector Biology and Control of Diseases, School of Public Health, Tehran University of Medical Sciences (TUMS), Iran Tahereh Sadat Asgarian Department of Vector Biology and Control of Diseases, School of Public Health, Tehran University of Medical Sciences (TUMS), Iran Ghazal Tashakori Department of Vector Biology and Control of Diseases, School of Public Health, Tehran University of Medical Sciences (TUMS), Iran Fateme Oroojalian Department of Advanced Technologies, School of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran Ameneh Mohammadi Natural Products and Medicinal Plants Research Center, North Khorasan University of Medical Sciences (NKUMS), Bojnurd, Iran Hassan Vatandoost Department of Vector Biology and Control of Diseases, School of Public Health, Tehran University of Medical Sciences (TUMS), Iran Saeedeh Ebrahimi Department of Vector Biology and Control of Diseases, School of Public Health, Tehran University of Medical Sciences (TUMS), Iran Seyed Hassan Moosa-Kazemi Department of Vector Biology and Control of Diseases, School of Public Health, Tehran University of Medical Sciences (TUMS), Iran 2026 06 21 2026 08 06 Background: Aedes aegypti is a primary vector of several clinically significant arboviruses. This study aimed to develop a nanoemulsion-based co-delivery system incorporating permethrin and Eucalyptus globulus essential oil for mosquito repellent applications. Methods: The essential oil composition of E. globulus was determined using gas chromatography-mass spectrometry (GC-MS). Nanoemulsions were formulated using a low-energy spontaneous emulsification method and characterized for stability, droplet size distribution, and zeta potential. The optimal formulation was further examined by transmission electron microscopy (TEM) and evaluated for cytotoxicity. The repellent activity of eucalyptus essential oil, permethrin, their combinations, and the eucalyptus essential oil-permethrin nanoemulsion was assessed against female Ae. aegypti mosquitoes using the arm-in-cage assay. Results: The nanoemulsions exhibited a mean droplet size of 93.5 nm and a zeta potential of 60–70 mV, indicating good stability. Transmission electron microscopy (TEM) confirmed the presence of spherical and uniformly dispersed droplets. The eucalyptus essential oil-permethrin nanoemulsion demonstrated strong repellency. A 3% permethrin concentration in the eucalyptus-permethrin nanoemulsion provided the maximum protection rate at 91.8%. In stability testing, the 1.5% version of the same nanoemulsion proved to be the most stable. Conclusion: Eucalyptus globulus essential oil, especially in nanoemulsion form and combined with permethrin, shows promise as a natural repellent formulation against Ae. aegypti. However, field trials are essential to confirm these findings under natural conditions. https://jad.tums.ac.ir/index.php/jad/article/view/1968 https://jad.tums.ac.ir/index.php/jad/article/download/1968/738