The authors provide comparative data derived during study of the time-course of changes in IgM, IgG and IgA and cellular eosinophilic and basophilic allergic reactions during application of pentoxyl and becotide alone and combined in multiple modality treatment of 161 patients with chronic obstructive bronchitis. Application of pentoxyl was accompanied mainly by quantitative increment of immunoglobulins, particularly IgA and IgG, and moderately pronounced desensitization effect that manifested by attenuation of the eosinophilic reaction and spontaneous degranulation of basophils. Application of becotide in multiple modality treatment led primarily to attenuation of the cellular allergic reactions under study and less marked increment of immunoglobulins. The combined use of the drugs for bronchitis exacerbation produced maximally pronounced desensitization (according to the eosinophilic reaction and basophil degranulation data) as compared to the effect of these drugs used alone on the patients' allergic status. It is recommended that patients with chronic bronchitis exacerbation should receive pentoxyl (during immunoglobulin deficiency and proneness to allergy), becotide inhalations to obtain primarily desensitization effect, and combined pentoxyl and becotide (in patients with high risk of sensitization).