The objective of the present work was to estimate the clinical, prophylactic, and microbiological effectiveness of fusafungine applied for the treatment of acute rhinosinusitis (ARS) in the children that develops as a consequence of acute stenosing laryngotracheitis. The study included 61 children presenting with ARS and concomitant acute stenosing laryngotracheitis (ASLT) that were treated with fusafungine (Bioparox). Both tolerance and safety of this preparation were evaluated. Fusaferine was prescribed after reduction of pharyngeal stenosis. The children were divided into two groups. Group 1 was comprised of the patients with the respiratory symptoms and rhinosinusitis (n = 36), group 2 consisted of the children with the respiratory symptoms in the absence of rhinosinusitis (n = 25). Subgroups of the children treated with fusafungine and without it were distinguished to estimate the clinical, prophylactic, and microbiological effectiveness of fusafungide. Within the first days after hospitalization, 59% of the children with diagnosis ASLT developed bilateral rhinosinusitis, in all probability of viral etiology. Fusafungine produced the clinically apparent effect in the patients with ASLT regardless of the presence of ARS. Specifically, this preparation decreased the degree of hypertrophy of pharyngeal tonsils three times faster than standard therapy; moreover, it reduced the requirement for systemic antibiotics by 1.9 times. The treatment with fusaferine prevented the development of acute bilateral rhinosinusitis in the children with ASLT and promoted compete decontamination of the nasopharynx from M. catarrhalis, Str. pneumonia, Str. pyogenes, H. influenza, Cor. s the nasopharynx pecies, E. faecalis, and C. albicans. The frequency of adverse reactions of organoleptic character was estimated at 16.6%.