<![CDATA[Mosquito repellent lotions containing synthetic active ingredients such as N,N-diethyl-meta-toluamide (DEET) are highly effective but may cause skin irritation, and other adverse health effects, highlighting the need for safer plant-based alternatives. This study aimed to develop a mosquito repellent lotion formulated with calamansi (Citrofortunella macrocarpa) essential oil as a natural active ingredient and to evaluate its physicochemical characteristics and repellent efficacy. The study employed a non-factorial completely randomized design (CRD) consisting of five concentrations of calamansi essential oil (0%, 5%, 10%, 15%, and 20%), with three replications per treatment. The evaluated parameters included emulsion stability, pH, homogeneity, spread ability, and mosquito repellent activity. The results showed that all formulations exhibited 100% emulsion stability, pH values within the acceptable range (7.53-7.56), and good homogeneity based on both visual and microscopic observations. Spreadability increased from 6.32 cm at 0% essential oil concentration to 7,53 cm at 20% concentration. Repellent efficacy increased significantly with increasing essential oil concentration, with the longest protection time of 118 minutes achieved by the formulation containing 20% calamansi essential oil. These findings indicate that increasing the concentration of calamansi essential oil enhances the mosquito repellent efficacy, demonstrating its potential as natural alternatives to synthetic DEET-based mosquito repellent lotions. ABSTRAK (Bahasa Indonesia) Losion antinyamuk berbahan aktif sintetis seperti N,N-diethyl-meta-toluamide (DEET) diketahui efektif, namun berpotensi menimbulkan iritasi kulit dan efek samping lainnya, sehingga diperlukan alternatif repelen yang lebih aman berbasis bahan alam. Studi ini bertujuan mengembangkan formulasi losion dengan komponen aktif minyak atsiri kalamansi (Citrofortunella microcarpa) sebagai opsi repelen alami, serta mengevaluasi karakteristik fisikokimia dan efektivitasnya sebagai penolak nyamuk. Penelitian menggunakan Rancangan Acak Lengkap (RAL) nonfaktorial dengan lima taraf konsentrasi minyak atsiri kalamansi, yaitu 0%, 5%, 10%, 15%, dan 20%, masing-masing diulang tiga kali. Parameter yang diamati meliputi stabilitas emulsi, pH, homogenitas, daya sebar, dan aktivitas repelen terhadap nyamuk. Hasil penelitian menunjukkan bahwa seluruh formulasi memiliki stabilitas emulsi 100%, pH berada pada rentang aman (7,53–7,56), serta homogen secara visual dan mikroskopis. Daya sebar meningkat dari 6,32 cm pada konsentrasi 0% menjadi 7,53 cm pada konsentrasi 20%. Aktivitas repelen meningkat signifikan seiring bertambahnya konsentrasi minyak atsiri, dengan waktu proteksi terpanjang sebesar 118 menit pada konsentrasi 20%. Hasil penelitian menunjukkan bahwa peningkatan konsentrasi minyak atsiri kalamansi mampu meningkatkan efektivitas losion sebagai repelen tanpa menurunkan mutu fisik sediaan, sehingga berpotensi dikembangkan sebagai alternatif repelen alami pengganti losion berbahan aktif sintetis.]]>
