Amalgam Contact Allergy in Oral Lichenoid Lesions

Background: Oral lichenoid lesions (OLLs) cannot be distinguished from oral lichen planus (OLP) except that causative factors can be identified. Amalgam is one of the causative allergens, and replacement may lead to resolution. Objectives: The aim of this study was to determine the prevalence, prognosis, and aggravating factors of amalgam contact allergy in patients with OLLs. Methods: A clinical retrospective and prospective cohort study was carried out at the Dermatology Department, Siriraj Hospital, Mahidol University. In cases with patch test positive for an amalgam component, patients were suggested to replace their amalgam restorations. Results: Of 53 patients with OLLs, 39 (73.6%) had positive patch test results, and 31 (58.5%) reacted to at least one amalgam component. The most common causative allergen was mercury (35.8%). Lesions on bilateral buccal mucosa and gingiva tended to have negative patch test results (P < 0.05). Spicy food was the main aggravating factor. Amalgam replacements were performed in 10 patients. Clinical improvement was observed in all cases with complete healing in 3 cases. Conclusions: The prevalence of amalgam contact allergy in patients with OLLs was 58.5%. Mercury was the most common allergen, followed by copper sulfate. An association between clinical, topographic relation, and positive patch test results would be a useful predictor for favorable outcome after amalgam removal.