Salivary gland swelling is a commonly encountered clinical symptom, but the establishment of a diagnosis is occasionally difficult. Here, we present two sialodochitis fibrinosa patients with recurring bilateral parotid swelling. In both patients, secretion of mucous plugs containing numerous eosinophils was observed from Stensen's ducts. As expected, the level of interleukin-5 in the saliva was much higher than that in the serum. One patient had no medical history of allergic disease; the other had allergic rhinitis which had never been associated with parotid gland swelling. Microbiological examination was unable to isolate significant bacterial specimens from the mucous plugs. Thus, although allergy and/or bacterial infection are reportedly implicated as causes of sialodochitis fibrinosa, there may exist other possibilities for its pathogenesis. Interleukin-5 seems to play a crucial role in the pathogenesis of sialodochitis fibrinosa.