Does mouthwash raise blood pressure and harm heart health?

Social media clips have suggested that using mouthwash might increase the risk of high blood pressure - and could even be harmful for heart health.

In some of these videos, the claim is that mouthwash wipes out “good” oral bacteria that support the cardiovascular system.

It’s an attention-grabbing idea, but it’s not a reason to bin your mouthwash. The evidence is much more nuanced.

Oral bacteria, nitric oxide and blood pressure

The mouth is home to many different bacteria. Collectively, they make up a varied, balanced microbiome that helps stop harmful microbes from overgrowing, supports normal metabolic activity, and contributes to oral health and general wellbeing.

A key job of certain oral bacteria is to convert nitrate from our diet (often from foods such as leafy green vegetables) into nitrite.

After nitrite is swallowed, the body can convert it into nitric oxide. This occurs through the nitrate–nitrite–nitric oxide pathway, also known as the enterosalivary pathway - one of the ways bacteria help keep the body functioning well.

Nitric oxide is important for controlling blood pressure and for supporting brain and muscle function.

This is why some online influencers argue that mouthwash harms heart health: by disrupting the “healthy” bacteria involved in nitric oxide production.

Mouthwash and heart health link

A number of small studies have shown that providing people with mouthwash can alter the mix of bacteria in the mouth. That shift may reduce how effectively oral bacteria convert nitrate (from vegetables) into nitrite, which the body needs in order to produce nitric oxide.

In one study involving 19 healthy volunteers, adults who used chlorhexidine mouthwash for seven days experienced a small rise in blood pressure alongside lower nitrite levels.

Another intervention study found that rinsing twice a day with 0.12% chlorhexidine gluconate mouthwash for one week significantly raised blood pressure in 27 healthy adults.

In a further trial of 15 adults who already had high blood pressure, using chlorhexidine for three days increased blood pressure even more.

What type of mouthwash was tested?

One crucial point that can get lost in social media summaries is which mouthwash these studies used.

Many of the studies linking mouthwash use to blood pressure changes gave participants chlorhexidine. This is a potent, over-the-counter antiseptic mouthwash that is typically only advised for short-term use - for example, for people with gum disease or after dental procedures where its antimicrobial action is useful.

Because chlorhexidine disrupts oral bacteria as part of infection control - including bacteria that convert nitrate into nitrite - it suits research looking at the nitrate–nitrite–nitric oxide pathway.

But that also means results from chlorhexidine studies may not represent what happens with gentler, everyday mouthwashes.

A trial in 12 healthy adults looked at how three different mouthwashes (plus gargling with water as a control) affected oral bacteria.

After participants drank nitrate-rich juice, researchers assessed how much nitrate oral bacteria converted into nitrite. Both water and a mild mouthwash (one without harsh ingredients such as chlorhexidine) produced the expected pattern, with nitrate being converted to nitrite.

By contrast, a cetylpyridinium chloride mouthwash (which also has strong antibacterial activity) partly blocked the conversion of nitrate to nitrite. The strongest chlorhexidine mouthwash nearly halted the process altogether.

That matches what you’d expect from their stronger antibacterial effects. These more powerful mouthwashes were also associated with higher systolic blood pressure.

Alcohol (ethanol) is another ingredient found in many mouthwashes, although products typically include other active components too, such as essential oils. This makes it hard to separate out alcohol’s specific role.

Because alcohol is antimicrobial, it may affect the oral microbiome. Some studies have even pointed to a possible association between alcohol-containing mouthwashes and an increased risk of oral cancer.

However, there are currently no studies that have specifically investigated ethanol-only mouth rinses and their effects on either the oral microbiome or cardiovascular health.

Overall, the evidence base suggests that the mild, over-the-counter mouthwash most people buy in shops is less likely to meaningfully disrupt nitrate-to-nitrite conversion or change blood pressure.

In a long-term study of 354 adults, stronger day-to-day oral hygiene habits - such as brushing and flossing - were associated with a lower risk of cardiovascular death over nearly 19 years. Regular use of mouthwash did not seem to affect heart health outcomes.

This finding applied to milder mouthwashes containing fluoride and alcohol, as well as stronger antibacterial mouthwashes such as chlorhexidine and cetylpyridinium chloride.

The type of mouthwash matters

Taken together, these studies indicate that some mouthwashes (including chlorhexidine) can disrupt beneficial oral bacteria and interfere with the nitrate–nitrite–nitric oxide pathway when used over the long term.

Even so, more research is needed to properly understand the long-term cardiovascular effects of other mouthwash types - including mild everyday brands and those that contain alcohol.

Because mouthwashes are formulated for different purposes, it’s worth checking the active ingredient listed on the back of the packaging. Alcohol-free and milder mouthwashes appear less likely than stronger products to affect the heart-supporting bacteria.

That said, it’s still important to read ingredient lists, as alcohol-free options can include antibacterial agents such as cetylpyridinium chloride.

The most sensible approach is to pick a product that matches your needs and to use it in moderation. Strong chlorhexidine mouthwashes are best kept for managing gum disease or treating oral infections.

It’s also important to remember that poor oral health and untreated infections can contribute to heart disease more broadly.

For instance, a systematic review of 82 studies concluded that chronic oral disease and tooth loss were associated with a higher risk of heart problems. This is one reason maintaining a healthy balance of mouth bacteria matters for more than just your teeth.

Look after both oral and overall health by brushing and flossing regularly, seeing your dentist, and choosing a mouthwash that works for you.

Joanna L'Heureux, Postdoctoral Researcher, Public Health and Sport Sciences, University of Exeter

This article is republished from The Conversation under a Creative Commons licence. Read the original article.