Introduction. It is well-known that any parapharmaceutical substance, in particular, foam-washing agents comprising water in combination with detergents, extracts, water-soluble vitamins, viscosity regulators, pH, etc., is the ideal environment for microbial growth. Therefore, it is indispensable to use preservatives to protect any foam-washing agent from possible contamination by microorganisms. Their main advantages are: presence of a single antimicrobial and antifungal effect, expanded range of effects, decrease in the risk of resistance of microorganisms and decrease in the toxicity and concentration of the preserving mixture. In this regard, the shelf life of parapharmaceutical substances is not provided through the use of large quantities of preservatives, but thanks to their rational combination. Materials and Methods. For this study, we have made a number of samples of foam washing bases with a number of preservatives, which are often used in developing foam-washing agents with acidic pH value, namely: sample number 1 – foam washing base + sodium benzoate; sample number 2 – foam washing base + «Euxyl K300» (phenoxyethanol, methylparaben, bulylparaben, ethylparaben, propylparaben, isobutylaraben); sample number 3 – foam washing base + «Germaben II» (polypropylene glycol, diazolium dinomovine, methylparaben, propylparaben); sample number 4 – foam washing base + «Nipaquard CMB» (benzyl alcohol, triethylene glycol, chloromethylisothiazoline, methylisothiazoline). The concentration of preservative in each sample was 0.1% (average concentration that is recommended for developing foam-washing agents). The antimicrobial activity of prototype gels was studied in vitro by diffusion in agar (“wells” method). The antimicrobial activity was measured immediately after sample preparation. All the studies were performed in aseptic conditions using a laminar box (biological safety cabinet AS2-4E1 "Esco" Indonesia). Results. According to the study, it was found that among the selected preservatives “Nipaquard CMB” was just the most active. When studying the antimicrobial activity of foam-washing agent samples with different concentrations of the preservative “Nipaquard CMB”, it was found that namely the sample with the concentration of “Nipaquard CMB” of 0,1% showed satisfactory results due to its antimicrobial activity against all cultures such as bacteria and fungi. Conclusions. On the basis of microbiological studies it has been demonstrated that all the selected preservatives such as sodium benzoate, “Euxyl K300”, “Germaben II” and “Nipaquard CMB” at a concentration of 0.1% have a broad spectrum of antimicrobial action and antimicrobial activity against all test strains used. We just chose «Nipaquard CMB» as a preservative at a concentration of 0.1% according to the results of experimental research, because it had the best results and a very high antimicrobial activity both against the bacterial cultures - Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pr. Vulgaris and in relation to the effect on fungal cultures – Candida albicans, Aspergillus brasiliensis.