Because of an ever increasing occurrence of oral allergic reactions, we embarked upon this study to find out their actual incidence and to identify the drugs causing such reactions, the clinical manifestations tending to occur orally and the duration of therapeutic treatment of drug-induced allergic reactions. This cinical trial included a group of 50 subjects with allergic reactions involving oral mucosa, ascertained by clinical and laboratory tests. Allergies affecting oral mucosa were found to occur in 3.6% of patients, 84.4% of them referring to drug-induced allergic reactions, with as much as 72,3% of them being induced by sulfanomides. In this study, the clinical oral manifestations most frequently observed were found to indicate the occurrence of stomatitis, fixed allergic eruptions and mucous edema. In 50 % of the subjects, oral lesions were successfully treated with antiallergic therapy with in a week. Thus we have concluded that allergic reactions in oral mucosa, especially those induced by drugs, sulfonamides in particular, represent a pathology which should be expected by a dental practitioner. The course of the disease can be substanially reduced by either topical or general antiallergic therapy.