Histopathologic Spectrum of Intraoral Irritant and Contact Hypersensitivity Reactions: A Series of 12 cases.

BACKGROUND: Irritant contact stomatitis (ICS) and contact hypersensitivity stomatitis (CHS) are often caused by alcohol, flavoring agents and additives in dentifrices and foods, and contactants with high or low pH. A well-recognized contactant for ICS is Listerine mouthwash, while that for CHS is cinnamic aldehyde. However, many other flavoring agents and even smokeless tobacco are contactants that cause mucosal lesions that are entirely reversible. The objective of this study is to 1) present cases of ICS and CHS with a clear history of a contactant at the site and the histopathologic features of the resulting lesion and 2) define the histopathologic features that characterize such lesions. METHODS: 12 cases of ICS and CHS with known contactants that exhibited distinct histopathologic patterns were identified. RESULTS: ICS are characterized by three patterns in increasing order of severity namely: 1) superficial desquamation, 2) superficial keratinocyte edema, and 3) keratinocyte coagulative necrosis with/out spongiosis and microabscesses. CHS is characterized by two patterns namely plasma cell stomatitis with an intense plasma cell infiltrate and a lymphohistiocytic infiltrate with or without non-necrotizing granulomatous inflammation. Three patterns of the latter are recognized: (1) lymphohistiocytic infiltrate at the interface with well-formed or loosely aggregated non-necrotizing granulomas; (2) lymphohistiocytic infiltrate at the interface with peri- and para-vascular lymphohistiocytic nodules; and (3) lymphohistiocytic infiltrate at the interface with peri- and para-vascular lymphohistiocytic nodules containing non-necrotizing granulomas. The same contactant may elicit ICS and CHS, while one histopathologic pattern may be brought on by various contactants. CONCLUSION: ICS and CHS have distinct histologic patterns. Recognizing that these patterns are caused by contactants would help clinicians manage such mucosal lesions.