Allergic palmoplantar pustulosis caused by cobalt in cast dental crowns: a case report.

Cobalt chrome alloy is a common material in prosthodontic restorations; however, instances of palmoplantar pustulosis owing to cobalt allergy are rare. Here, we report an unusual case of palmoplantar pustulosis in the hands and feet of a 58-year-old male patient caused by a cobalt allergy. The patient developed palmoplantar pustulosis characterized by redness, pustules, vesicles, and scaly erythema on his hands and feet 1 month after obtaining cobalt chromium alloy cast crowns on his molar teeth. The symptoms persisted for 1 year. He underwent standard patch testing, which showed a strong positive reaction to cobalt chloride. After the crowns were removed, the symptoms disappeared in 3 weeks. This study may serve to remind dental practitioners to be aware of potential allergic reactions to dental materials used in prosthodontic treatment and to enable them to recognize a metal allergy if it appears.