The Risks: When Mouthwash Can Be Bad for Oral Health

Despite its benefits, mouthwash can also pose risks—especially when used incorrectly, excessively, or with the wrong formulation. One of the most common risks is dry mouth (xerostomia). Many mouthwashes, particularly those containing alcohol, can dry out the mouth by reducing saliva production. Saliva is the mouth’s natural defense against bacteria: it washes away food particles, neutralizes acid, and remineralizes enamel. A dry mouth increases the risk of cavities, bad breath, and oral infections like thrush. A 2025 study by the International Dental Federation (FDI) found that 30% of people who use mouthwash daily experience dry mouth symptoms, with alcohol-based rinses being the primary culprit. For people already prone to dry mouth—such as those taking medications for high blood pressure, diabetes, or depression—alcohol-based mouthwashes can exacerbate the condition.

Another significant risk is the disruption of the mouth’s natural microbiome. The mouth is home to a complex ecosystem of bacteria—some beneficial, some harmful. A healthy microbiome balances these bacteria, but antimicrobial mouthwashes (especially those with strong ingredients like chlorhexidine) can kill both good and bad bacteria, leading to an imbalance (dysbiosis). This imbalance can make the mouth more susceptible to harmful bacteria, increasing the risk of cavities, gum disease, and even systemic health issues. Recent research published in the Journal of Oral Microbiology found that long-term use of chlorhexidine mouthwash can reduce the diversity of beneficial bacteria in the mouth, potentially undoing some of its positive effects. Additionally, overuse of antimicrobial mouthwashes may contribute to antimicrobial resistance, making it harder to treat oral infections in the future.

Other risks include enamel damage and tooth staining. Some mouthwashes contain acidic ingredients (like citric acid or hydrogen peroxide) that can erode enamel over time, especially if used excessively or by people with already weakened enamel. Hydrogen peroxide-based mouthwashes, often marketed for whitening, can cause sensitivity and enamel damage if not used as directed. Certain ingredients, such as chlorhexidine, can also cause temporary tooth staining or discoloration of the tongue, especially in people who drink coffee, tea, or red wine. For children under the age of 6, mouthwash poses a particular risk: their swallowing reflexes are not fully developed, and accidental ingestion can cause nausea, vomiting, or even intoxication (especially with alcohol-based rinses). The ADA and WHO strongly recommend that children under 6 do not use mouthwash unless directed by a dentist.

Debunking Common Myths About Mouthwash

Misinformation about mouthwash is widespread across the globe, leading people to use it in ways that either negate its benefits or cause harm. One of the most dangerous myths is: “Mouthwash can replace brushing and flossing.” This couldn’t be further from the truth. As mentioned earlier, mouthwash cannot physically remove plaque—only brushing and flossing can do that. Relying on mouthwash alone is like sweeping a dusty floor but never picking up the dirt: it may mask the problem but won’t solve it. A 2024 survey by the FDI found that 25% of adults worldwide believe mouthwash can replace brushing, and these individuals are 40% more likely to develop cavities and gum disease.

Another prevalent myth is: “The stronger it stings, the better it works.” Many people associate a burning sensation with effectiveness, but this is often caused by alcohol or high concentrations of menthol—ingredients that irritate the mouth’s mucous membranes and dry out the mouth. Gentle, alcohol-free mouthwashes can be just as effective at reducing bacteria without the stinging or irritation. A third myth is: “All mouthwashes are the same.” As we’ve discussed, cosmetic and therapeutic mouthwashes serve very different purposes—cosmetic rinses only mask bad breath, while therapeutic ones address specific oral health issues. Choosing the wrong type of mouthwash (e.g., using a cosmetic rinse to treat gingivitis) will not provide any health benefits and may even delay proper treatment.

A fourth common myth is: “Mouthwash cures bad breath.” While therapeutic mouthwashes can reduce the bacteria that cause bad breath, they cannot address the root causes—such as poor oral hygiene, gum disease, dry mouth, or systemic health conditions like diabetes or liver disease. Using mouthwash to mask bad breath without addressing these underlying issues can lead to more serious problems. Finally, some people believe that “natural mouthwashes have no risks,” but this is false. Natural ingredients like essential oils can still cause irritation or allergic reactions in some people, and unregulated natural mouthwashes may not have been tested for safety or effectiveness.