We saw a video circulating on TikTok, showing a man pouring mouthwash down a toilet, captioned: “In your 30s, your cardiologist will tell you to pour your mouthwash down the toilet. It is very important that you take this advice seriously.” The video has gone viral, with over 37,000 likes at the time of writing.
According to the caption of the post, the reason mouthwash supposedly harms the heart is that it kills off oral bacteria that the body needs to keep the heart functioning properly. Mouthwash kills the bacteria on your tongue that produce 50% of your body’s nitric oxide- the molecule that keeps blood vessels flexible. Without this nitric oxide, people had a 49% higher diabetes risk and nearly double the risk of high blood pressure.
Looking into this, we found that the claim is a distorted version of real, ongoing research into what scientists call the nitrate–nitrite–nitric oxide pathway, also known as the enterosalivary pathway. This pathway involves oral bacteria converting nitrate from foods such as leafy greens into nitrite, which the body then turns into nitric oxide – a molecule that helps regulate blood pressure. A 2019 study published in Frontiers in Cellular and Infection Microbiology found that chlorhexidine, a strong antiseptic compound found in some mouthwashes, killed nitric oxide-producing bacteria and was linked to a rise in systolic blood pressure after a week of twice-daily use.
However, the effect is not uniform across all mouthwash. As Joanna L’Heureux, a postdoctoral researcher at the University of Exeter, explained in an analysis for The Conversation, most of the studies linking mouthwash to raised blood pressure used chlorhexidine which is typically reserved for short-term use in people with gum disease, rather than the milder, alcohol- or fluoride-based products most people buy over the counter. A trial comparing different mouthwashes found that a mild, everyday formula produced a normal nitrate-to-nitrite conversion, while cetylpyridinium chloride partially blocked it and chlorhexidine almost completely stopped it – with the stronger products linked to higher systolic blood pressure.
Crucially, a rise in blood pressure is not the same as a diagnosis of heart disease. One 19-year study of 354 adults found that regular mouthwash use, including antibacterial formulas such as chlorhexidine and cetylpyridinium chloride, was not associated with cardiovascular death, whereas poor routine oral hygiene, such as inconsistent brushing and flossing, was. A separate study tracking 540 adults did find that using mouthwash twice a day or more was associated with a higher rate of newly diagnosed hypertension over time, but even its authors note this reflects an association rather than a proven cause as this was an observational study, and further research must be done to directly attribute associations between mouthwash use to hypertension and heart disease risks.
Therefore, the claim that mouthwash causes heart disease is misleading.
It is true that certain strong, antiseptic mouthwashes can disrupt the oral bacteria involved in regulating blood pressure, and this is an area researchers are still actively studying. But the leap from this to “mouthwash causes heart disease”, and advice to stop using it altogether, is not supported by the evidence. The type of mouthwash matters: milder, everyday formulas appear far less likely to have this effect than the stronger antiseptic products the studies actually tested. Anyone concerned about the ingredients in their mouthwash is better off checking the label or asking their dentist, rather than taking a viral video’s word for it.
