Introduction. Imidourea is widely used as an antibacterial preservative in the pharmaceutical and cosmetic industries. There are literature data on the toxicity and specific effect of the substance, but there are no hygienic standards in the air of the working area necessary to protect the health of workers. The study aims to substantiate the approximate safe level of exposure (ASLE) of imidourea in the air of the working area based on the study of the nature of biological action in various ways of entry into the body. Materials and methods. The researchers chose the methods for studying the functions of organs and systems of experimental animals after a single inhalation of the substance at concentrations of 35.3±5.7 mg/m3 and 6.1±1.7 mg/m3 taking into account the literature data on the biological effect of the compound under study. We studied the antimicrobial effect of the substance on the intestinal microbiota of rats after 24 hours and 144 hours after inhalation exposure. Results. During inhalation of the substance in both concentrations, the researchers observed disturbances in the balance of the intestinal microflora, which were characterized by changes in the number of individual representatives of the normal microbiota, which corresponds to the initial signs of dysbiosis of the 1st degree. 144 hours after exposure, the microflora balance was almost restored. Inhalation exposure to imidourea at a concentration of 35.3 mg /m3 also revealed changes in the functional parameters of the liver (decreased activity of alkaline phosphatase and glucose concentration in blood serum) and kidneys (decreased content and rate of protein excretion in urine). Conclusion. Imidourea in the inhalation route of admission has a general toxic, sensitizing, weak antimicrobial effect. We recommend to use the ASLE of imidourea in the air of the working area of 1.5 mg/m3 (aerosol). Ethics. The Ethics Commission of JSC "VNC BAS" adopted and approved the imidourea research program (Protocol No. 3 of 11.02.2020).