This article reports on a 53-year-old woman suffering from recurrent diarrhea since 1980 who, in November 1988, was admitted to the Medical Department of the University of Erlangen-Nuremberg with four to eight loose to liquid stools a day. Since January 1988, in addition to abdominal symptoms, including meteorism and recurrent abdominal pain, intermittent bouts of fever of up to 40 degrees C lasting six to eight hours and frequently occurring in the evening, had been noted. The patient's symptoms improved at weekends and during the holidays. Since 1977, she had been employed at a cheese counter, selling cheese. Noteworthy findings were an eosinophilia of 6% and, with the prick skin test, weakly positive reactions induced by two moulds with no increased total IgE and negative IgE RAST for diverse foods and moulds. An in vitro histamine-releasing test performed on colonic mucosal particles obtained at colonoscopy, a sensitization of the mucosa to moulds was demonstrated, and the patient was then given the mast cell stabilizing agent DNCG. This treatment cleared the symptoms, and she put on weight. In vitro tests on colonic biopsy material repeated in 1989 revealed a significant reduction in the release of histamine in response to the anti-allergic treatment.