The present invention provides an adjunctive agent and a method for lavaging the alimentary canal, which is able to reduce a dose of oral cleaning agent for lavaging the alimentary canal and is capable of realizing an excellent cleaning effect at the time of use of the oral cleaning agent. The adjunctive agent comprises butyric acid bacterium (for example, Clostridium butyricum and the like) and/or lactic acid bacterium (for example, species belonging to the genus Lactobacillus and the genus Bifidobacterium).
