The article presents data study of acute toxicity of the drug “Ciflur”. Nodular dermatitis causes significant economic losses due to a temporary decrease in milk productivity, temporary or permanent sterility of breeding bulls, skin lesions, and death of sick animals due to secondary infections. Specific treatments have not been developed. Preventive disinsection of livestock premises is effective for prevention. For this purpose, a new drug “Сiflur” was developed. 1 ml of the drug contains the active substance: cyfluthrin – 10.0 mg. Toxicity studies of the drug and evaluation of the results were performed in accordance with standard methods. The study of acute toxicity of the drug “Сiflur” when applied to the skin was performed on 18 white rats weighing 170–190 g. The animals were divided into 3 groups of 6 heads. Rats were kept in the vivarium in accordance with sanitary rules and on a standard diet adopted in the vivarium with the use of compound feed. The first group of rats on the skin was applied the drug “Сiflur” at a dose of 1250 mg/kg, the second – 2500 mg/kg body weight. The third group of rats was a control – these animals on the skin was applied Solveso 200 solvent in the amount of 2500 mg/kg body weight. Acute toxicity of the drug was studied when applying the drug to a pre-cut area of skin on the back, which was at least 10 % of the total surface area of the animal. In order to prevent excessive spreading on the skin, the drug was applied slowly, drying with warm air with a hair dryer. For 14 days after cutaneous application of the drug was recorded daily its effect on the survival of rats, the appearance of rats and manifestations of physiological disorders of animals. Rats were weighed before application, as well as 3, 7 and 14 days after the start of the study. After 14 days, an autopsy was performed and the condition of the internal organs was examined for possible impressions, and the internal organs were weighed and their relative weight coefficients were calculated. Therefore, a single skin application of “Ciflur” at doses of 1250 and 2500 mg/kg body weight did not result in the death of experimental rats. The acute LD50 of the drug “Сiflur”when applied to the skin exceeds 2500 mg/kg body weight, which allows it to be classified as hazard class 4 according to the International Standard GOST 12.1.007-76, or category 5 according to the International Global Classification of Harmonized System (GHS). Only the application of “Ciflur” at the highest dose (2500 mg/kg body weight) caused a slight short-term reddening of the skin in some experimental rats, which disappeared without intervention for 4–8 hours.