The dangers of antibacterial mouthwash: Why, as a doctor, I never use them

Advertising and marketing strategies portray these products as an effective solution for fighting plaque, bad breath, and gum disease without highlighting any of the down sides. As a result, hundreds of thousands of consumers see them as healthy when, in fact, they are not.

Prolonged use of antibacterial mouthwashes can lead to unintended health consequences in the mouth and recent research has raised important questions about their safety for the rest of our bodies.

Antibacterial mouthwashes are designed to kill or inhibit the growth of all bacteria in the mouth via a variety of chemicals. These include a strong antibacterial agent called cetylpyridinium chloride, and chlorine dioxide which is also claimed to treat bad breath (halitosis) by breaking down sulfur compounds in the mouth. The disinfectant chlorhexidine is added to some mouthwashes and toothpastes and can leave brown patches on the enamel because it reacts with food left on the teeth, particularly tannins in cola, tea, coffee and red wine.

For people who don’t clean their teeth properly or for short term use, they may have a role. The problem is, the human mouth contains more than just harmful bacteria. It is home to a complex and balanced ecosystem of micro-organisms, many of which play essential roles in keeping the mouth and the rest of the body healthy. This bacterial flora, known as the oral microbiome, helps regulate pH levels, protect teeth and gums, starts the digestive process and even contributes to the body’s overall immune response.

One of the primary concerns with frequent and indiscriminate use of antibacterial mouthwashes is their potential to disrupt this oral microbiome. Unlike targeted antibiotics or certain medicated mouthwashes prescribed by dentists, most over-the-counter antibacterial rinses do not distinguish between harmful bacteria and beneficial bacteria. As a result, they can wipe out both, upsetting the natural balance of microbes in the mouth.

Antibacterial mouthwashes can be useful - but can also do more harm than good | Canva

Although the mouth may seem clean immediately after use, pathogenic (bad) bacteria usually grow back more quickly than the healthy bacteria, and in greater numbers, especially if sugary foods have been eaten after use, thereby actually promoting bad breath and increasing the risk of caries.

By killing beneficial bacteria, these mouthwashes can inadvertently increase the ratio of bad to good bacteria, hence reduce the mouth’s ability to protect itself against harmful invaders. Paradoxically, this can make individuals more susceptible to the very conditions they are trying to prevent, such as infections, inflammation, and oral diseases such as gingivitis and periodontitis. Some studies have even linked the overuse of alcohol-based mouthwashes with an increased risk of oral cancer as it allows cancer-causing substances such as nicotine to permeate the lining of the mouth more easily

Some mouthwashes, especially those which are alcohol-based, can cause a dry mouth, and reduced levels of protective mucus and saliva. Saliva is crucial for maintaining a healthy environment in the mouth by helping to neutralise acids, wash away food particles, and control bacterial growth. As well as being uncomfortable, reduced saliva flow can lead to an increased risk of cavities, gum disease oral thrush, mouth ulcers and bad breath.

Mouthwashes and general health

Another surprising potential risk associated with antibacterial mouthwashes is their possible impact on cardiovascular health. The process of digestion begins in the mouth, helped by healthy bacteria which are especially important for their capacity to reduce nitrate in foods to nitric oxide. Nitric oxide plays a vital role in regulating blood pressure by helping blood vessels relax.

Studies have shown that individuals who used antibacterial mouthwashes twice a day experienced a rise in blood pressure. High blood pressure requires medication, which has side effects, in order to reduce the increased risk of heart disease and stroke.

More worryingly, cohort studies have demonstrated that antiseptic mouthwashes are associated with a higher death rate in hospitalised patients. The authors of these studies believe this is also due to the disturbance in nitric oxide homeostasis. As well as helping to reduce blood pressure, nitric oxide is essential in multiple physiological processes, and a reduction its bioavailability is associated with the occurrence or worsening of chronic pathologies, such as atherosclerosis, diabetes which can lead to life threatening events such as ischaemic heart events or sepsis.

An altered oral microbiome also contributes to excess inflammation in the body. Chronic inflammation is associated with an increased risk of cancer and dementia.

In conclusion, antibacterial mouthwashes may seem like a quick fix for maintaining oral hygiene, but their overuse can lead to unintended mouth and systemic consequences. Given these potential risks, experts recommend using antibacterial mouthwashes with caution.

While they can be helpful in certain situations - such as after dental surgery, for short-term treatment of gum disease, or in cases where an individual is at high risk for oral infections - they should not be used as a daily preventive measures.

Instead, many dentists and doctors agree a more balanced approach to oral hygiene is encouraged. Regular brushing with fluoride toothpaste, flossing, and maintaining a healthy diet can go a long way in preventing oral health issues without the need for antibacterial agents. Additionally, non-antibacterial, oil based mouthwashes that focus on freshening breath or neutralizing acids may offer a safer alternative for everyday use. For more information please see these 12 tips to maintain oral hygiene.