Abstract
<title>Abstract</title> <p> <italic> <bold>Background</bold> </italic> : Mosquito-borne diseases, such as malaria, remain a major public health concern in Ethiopia and elsewhere globally. While synthetic repellants are effective, their repeated use has been associated with skin irritation, allergic reactions, and environmental concerns. Natural repellents, like essential oils from <italic>C. nardus</italic> and <italic>E. globulus</italic> , offer promising repellent and therapeutic advantages. However, the dermal safety of their combined use has not been scientifically evaluated. <italic> <bold>Objectives:</bold> </italic> To evaluate the acute and sub-acute dermal toxicity of a combined <italic>Cymbopogon nardus</italic> and <italic>Eucalyptus globulus</italic> formulation on hematological, biochemical parameters, and histopathology of the skin, kidney, and liver of albino Wistar rats. <italic> <bold>Methodology</bold> </italic> : The plant material was harvested about 270 kilometers south of Addis Ababa, in the Wondogenet region. The formulation was prepared by the Traditional and Modern Medicine Research Directorate of the Armauer Hansen Research Institute (AHRI). Essential oils were extracted by hydro distillation using a Clevenger-type apparatus. A topical formulation was prepared by incorporating essential oils of <italic>C. nardus</italic> and <italic>E. globulus</italic> (2 mL each; 1:1, v/v) into 100 g of white petrolatum, corresponding to approximately 3.5% w/w total essential oils based on estimated density. Acute dermal toxicity was evaluated following OECD guideline 402, while sub-acute (28-day) dermal toxicity was assessed according to OECD guideline 410. Forty adult albino Wistar rats (8–12 weeks old) were randomly assigned into four groups (n=10 per group; 5 males and 5 females). The test groups received dermal applications of 250, 500, and 1000 mg/kg body weight/day of the formulation, while the control group received the vehicle (white petrolatum). The formulation was applied once daily to approximately 10% of the shaved dorsal skin for 28 consecutive days. Hematological and biochemical parameters were analyzed at the end of the study. Following euthanasia under sodium pentobarbital anesthesia (150 mg/kg), the liver, kidneys, and skin were collected for Histopathological evaluation. <italic> <bold>Result</bold> </italic> : The dermal mean lethal dose LD50 of the <italic>C. nardus</italic> and <italic>E. globulus</italic> formulation was found to be above 5000mg/kg b.w, placing the formulation in GHS category 5 (Lowest toxicity). No mortality or clinical sign of toxicity was observed in either study. There were no significant differences (P>0.05) in body weight gain, food intake, and water intake, hematological indices, serum biochemical markers, or relative organ weights between treated and control groups. Histopathological examination revealed normal architecture of liver, kidneys, and skin across all dose groups. <italic> <bold>Conclusion</bold> </italic> : The combined <italic>C. nardus</italic> and <italic>E. globulus</italic> formulation did not produce observable acute or sub-acute dermal toxicity in Wistar rats at the tested doses. These findings indicate a favorable short-term dermal safety profile in this animal model. </p>