Systemic allergic contact dermatitis associated with allergy to intraoral metals.

Contact (allergic) dermatitis is a skin disorder related to natural exposure to various allergens. Systemic contact dermatitis (SCD) describes a cutaneous eruption in response to systemic exposure to an allergen. The exact pathologic mechanism remains uncertain. Herein we describe a 36-year-old woman with symmetric systemic allergic contact dermatitis, unresponsive to conventional treatment, associated with dental alloy-contact hypersensitivity. We did skin patch testing and the blood lymphocyte transformation test (LTT) from the dental allergen series to assess contact allergy to restorative dental materials. On patch testing, positive allergic contact dermatitis reactions to metals occurred (nickel, potassium dichromate, and gold). Nickel hypersensitivity was confirmed by LTT, which also revealed silver-amalgam sensitization. Our case report highlights the need to consider adverse reactions to base-metal dental alloys in the differential diagnosis of cases of systemic allergic contact dermatitis.