It’s a daily routine more than 200 millions Americans partake in, but a growing number of health experts are warning about the negative effects of mouthwash. 

While mouthwash is part of healthy oral hygiene recommended by dentists to reduce bacteria, prevent gum disease, fight bad breath, and strengthen teeth, not all solutions are equal. 

As well as killing off harmful bacteria, studies have shown that some mouthwashes contain ingredients such as chlorhexidine or alcohol, which can kill microbes that make nitric oxide.

Nitric oxide is a chemical produced when breaking down food, and its presence has been linked to improved blood pressure and better heart health. 

Experts have also suggested nitric oxide could help immune cells communicate – leading them to respond faster to an infection.

It has also been claimed that it can improve muscle performance by allowing cells to work faster.

Dr Jeremy London, who is based out of Georgia, also advises against using mouthwash. 

It’s a daily routine more than 200 millions Americans partake in. But a growing number of health experts are warning about the negative effects of mouthwash

In a TikTok video, he explains that as a cardiac surgeon, it is the one household staple that he ‘absolutely avoids’.

Like Dr Kahng he warns that the breath-freshening agent can kill healthy bacteria that helps control your blood pressure. 

He points out that this can then have a knock-on effect, as high blood pressure ‘is a risk factor for both strokes and heart attacks.’

Dentists are also telling people to watch out for – and avoid – washes that contain alcohol.

Alcohol is a common ingredient in mouthwashes as it helps to dissolve active ingredients like essential oils for plaque and gingivitis efficacy.

But California-based dentist Dr Joyce Kahng says that popular brands with alcohol in them ‘disrupt the oral microbiome’ – the diverse community of microorganisms, including bacteria, fungi, and viruses, that live in the mouth and throat

The alcohol content varies depending on the specific product, but it typically ranges from 14 percent to 27 percent by volume. 

Dr Kahng added in a TikTok that alcohol also dries out the mouth.

When saliva production is reduced, it can cause discomfort, bad breath, and even contribute to other oral health issues.

And for pregnant women, it’s even more important to avoid alcohol-based mouthwashes as ‘you are assumed to swallow around 15 percent of your oral hygiene products,’ the dentist added.

‘[Some mouthwashes] have a higher alcohol content than wine,’ she adds.

Finally, Dr Kahng warns that many mouth washes are acidic, with pH levels ranging from three to six, which can be harmful to tooth enamel and gums, especially for those with receding gums or sensitivity.

A pH below 5.5 is generally considered potentially erosive to teeth.

California-based dentist Dr Joyce Kahng says that Listerine – which promotes itself as the ‘number one dentist and hygienist recommended mouthwash brands – is the worst offender in her book as it ‘disrupts the oral microbiome’

To solve bad breath, Dr London suggests some alternatives to mouthwash, including flossing and tongue scraping.  

He tells viewers: ‘Now look, using mouthwash is a personal choice. I did it for many years until I was educated. Your body, your choice. Inform yourself, understand the data and make good decisions.’

Backing up Dr Kahng and Dr London’s claims, in 2019 researchers at the University of Puerto Rico found that people who used mouthwash twice a day or more had a greater risk of having high blood pressure compared to less frequent users.

And an earlier study, in 2017, by the same Puerto Rico-based research group found that overweight people using mouthwash at least twice daily had a 50 percent increased risk of developing type 2 diabetes over a three-year period compared to non-users.

The researchers put this down to the fact that killing these key bacteria in the mouth reduces the body’s ability to make nitric acid, a natural compound that plays a role in regulating insulin – the hormone that keeps blood sugar levels steady. 

Therefore, the destruction of this beneficial bacteria could lead to unstable blood sugar peaks and encourage the development of diabetes.

And that’s not the only potentially harmful side-effect of mouthwash.

A 2020 study published in the Journal of Intensive Care Medicine found that antiseptic mouthwash used by patients who have been hospitalized may increase their risk of death from sepsis – this is a life-threatening condition that occurs when the body’s immune system overreacts to an infection, leading to organ failure which can be fatal.

Scientists aren’t entirely sure what is behind the increased risk but suggest that killing the oral bacteria responsible for nitric acid production stops the body being able to absorb enough of this compound, which plays a key role in healthy circulation – and we know that circulation is one of the body systems that shuts down in sepsis.

Last year, Listerine users sued the mouthwash’s manufacturer Johnson & Johnson over claims it put them at risk of cancer.

A previous study found the company’s Cool Mint flavor mouthwash increased levels of mouth bacteria linked to throat and colon cancer.

The $5 mouthwash tells consumers to use it for 30 seconds twice a day to kill 99.9 percent of all the bacteria in their mouth.

But research suggests daily uses causes levels of two species of bacterium — Fusobacterium nucleatum and Streptococcus anginosus — to rise.

These have been linked to cancer in the esophagus — the tube that connects the throat and the stomach — and in the colon.

Researchers from the Institute of Tropical Medicine in Belgium also saw a decrease in a group of bacteria called Actinobacteria, which may protect against cancer by helping to reduce inflammation.

A spokeswoman for Kenvue, formerly part of Johnson and Johnson, said in response to the findings that were published last year: ‘Studies on the impact of Listerine on oral health have been published in hundreds of peer-reviewed publications for more than a century, making it one of the most extensively tested mouthwash brands in the world.

‘We continuously evaluate the latest science and monitor safety signals to evaluate the benefit risk profile of our products.’

She added: ‘Listerine is safe when used as directed on the label, and there is no evidence that Listerine causes cancer.’