Delayed and immediate hypersensitivity reactions associated with the use of amalgam.

Hypersensitivity to the constituents of dental amalgam is uncommon. When it occurs it typically manifests itself as a lichenoid reaction involving a delayed, type IV, cell-mediated hypersensitivity response. Rarely, a more acute and generalised response can occur involving both the oral mucosa and skin. We describe two cases that illustrate the presentation and management of these two types of reaction.