The article presents the results of a study of the diagnostics of erythema multiforme exudative. We studied the microbiological and immunological characteristics of this pathology. The combination of pathogenic microorganisms forms oral dysbiosis. The pathogenetic significance of immunity disorders and nonspecific resistance of the body, which we identified in patients with erythema multiforme exudative, convincingly showed the need for immunomodulatory therapeutic measures in them.