1. Considering an imaginable important role of histamine in inflammations or allergic reactions, some clinical and experimental studies were made for the purpose of findings the relationship of the pathological changes of A. P. to local histamine. 2. Gingivae in the case of A. P. showed a remarkable quantitative increase of histamine, compared with those in the case of normal healthy controls. It could be noticed that this increase had an increasing tendency in proportion to the degree of inflammatory pathologic changes in the gingiva. 3. In the gingivae of A. P. an increase of mast cells and their morphologic changes, particularly disintegration, were seen and the grade of changes was almost parallel to an increase of histamine. 4. When a histamine solution was repeatedly injected into the mucobuccal folds of animals, a remarkable increase of histamine and mast cells in the injected gingivae were recognized with inflammatory changes. An increase of gingival histamine could be hardly recognized by means of a simple mechanical stimulation or local anaphylaxis alone. However, in the combination of two, the increase of histamine was seen and relatively
remarkable inflammatory changes suggestive of A. P. were macroscopically and microscopically noticed. 5. Topical applications of the ointment mixed with sinomenine, histamine-liberating substance, and benadryl, antihistamine substance, repeated every other day in the gingival pockets, showed favorable effects in slight or early cases of A. P. 6. These observations suggest the existence of both possible role of histamine in the development of local pathologic condition of A. P. and allergic processes in etiologic factors of the disease.</p
