Can mouthwash raise your blood pressure?
Antibacterial mouthwash disrupts the bacteria in your mouth that contribute to healthy blood vessels. Whether daily use meaningfully raises blood pressure in practice has not yet been established.
Chlorhexidine mouthwash does not only kill harmful bacteria; it also kills the bacteria in your mouth that convert nitrate (from vegetables such as beetroot) into nitrite. That nitrite is an intermediate step your body uses to produce nitric oxide, a substance that widens blood vessels. One overview of studies found, across all five studies examined, that antibacterial mouthwash lowered nitrite levels in saliva, and in three of those five studies also in the blood.
Whether mouthwash actually drives blood pressure up is less certain. Four of five smaller studies saw a rise after antibacterial mouthwash use. But two larger analyses, each combining five studies, ultimately found no meaningful rise. The measured differences were around 1.5 mmHg (millimetres of mercury, the unit for blood pressure), which remains close to zero. The researchers themselves point to considerable contradictions between the individual studies.
A hospital analysis spanning nearly ten years found a striking association: people who had used chlorhexidine mouthwash were diagnosed with high blood pressure three times as often. But this type of research cannot prove cause and effect. People who regularly need dental treatments involving chlorhexidine may also have a higher heart and blood vessel risk for other reasons.
One hint that age may play a role: in older adults (67 to 79 years), beetroot juice lowered blood pressure by an average of 4 mmHg, while antiseptic mouthwash affected blood vessel function in younger people but not in older ones. This suggests that the route from mouth bacteria to blood pressure does not work equally strongly in everyone.
Short-term use of antimicrobial mouthwash (21 days) had no clinically relevant effect on blood pressure in a small study, and any changes in pulse pressure resolved on their own. People using mouthwash for a specific dental health complaint do not need to stop right away, but those concerned about their blood pressure are best advised to avoid using it daily over a long period.
This answer draws on five overviews of studies, two studies in people with random assignment, and one large hospital analysis. The overviews agree on how mouthwash works (it lowers nitrite levels in the mouth), but partly contradict each other on the blood pressure effect. The two most recent large combined analyses find no meaningful effect on blood pressure; the older, smaller studies do. The researchers behind those combined analyses themselves point to large differences between the individual studies as a reason not to draw firm conclusions. The hospital analysis shows a strong link but cannot prove that mouthwash is the cause.