Contact stomatitis due to palladium and platinum in dental alloys

We report a patient with contact stomatitis due to combined sensitization to palladium and platinum. Patch testing showed strong and persistent allergic patch test reactions to palladium chloride (1% pet.), ammonium tetrachloroplatinate (0.25% pet.), and a palladium metal plate. A platinum metal plate showed a weaker reaction. Histological examination of a biopsy from the test site of palladium chloride (1% pet.) at D3 showed both eczematous and lichenoid changes.