Repeated use of over-the-counter (OTC) mouthwash was linked to a higher risk of developing prediabetes and diabetes in a study of more than 1,000 adults who have excess weight or obesity. For many individuals, use of OTC mouthwash is part of their regular oral hygiene care. The potential adverse effects of long-term daily use, however, have not been investigated. Study authors explained that using antibacterial mouthwash can eradicate oral microbes needed for nitric oxide formation and place the user at risk for metabolic disorders. The study found that adults who used mouthwash at least twice daily had a significantly increased risk of developing prediabetes or diabetes, compared with less frequent users or those who never used mouthwash. Researchers analyzed data for 1,206 adults who have excess weight or obesity, and without diabetes or major cardiovascular disease, ages 40 to 65. Patients were followed for 3 years. Patients had no diabetes or major cardiovascular disease; 945 patients had complete follow-up data for analyses. The data showed that 43% of patients used mouthwash at least once a day and 22% used mouthwash at least twice a day. Adults who used mouthwash at least twice a day at baseline showed a significantly increased risk of prediabetes/diabetes vs. those who used it less frequently (HR 1.67, 95% CI: 1.24–2.26) or never used mouthwash (HR 1.65, 95% CI: 1.19–2.28). The size of the effects we’re consistent after factoring in income, education, oral hygiene, oral conditions, sleep breathing disorders, diet, medications, HOMA-IR, fasting glucose, 2-hour post-load glucose, or C-reactive protein to the multivariate models.  From the results it was concluded that, participants who used mouthwash less than twice a day did not demonstrate a risk, suggesting that the effect starts at a threshold of use of twice a day or more.–Published in Nitric Oxide, Available online 20 September 2017