PURPOSE: This study aimed to investigate the relationship between dental metal allergy, periodontitis, and palmoplantar pustulosis among patients from a dental metal allergy clinic over a period of 8 years. METHODS: This study included 436 patients who visited our dental metal allergy clinic between April 1, 2009 and March 31, 2016. Diagnoses of skin diseases, periodontal records, dental metal series patch test results, and electron probe microanalysis (EPMA) data were obtained from medical records. Relative risk (RR) values were estimated from these data. RESULTS: Of the 359 patients who underwent the patch test, 241 showed a positive reaction. Of the 187 patients who underwent EPMA, 113 had allergenic metals in their dental prostheses. These patients were suspected to have a dental metal allergy. Furthermore, 150 of the 436 patients were diagnosed with palmoplantar pustulosis (PPP). The RR of metal allergy between patients with PPP and healthy subjects was 3.88. The RR of periodontal disease between patients with PPP and PPP-negative patients in the national average was 2.54. CONCLUSIONS: In this study, both dental metal allergy and periodontitis showed a high RR for PPP.