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July 12, 2024 — Many people use mouthwash as part of their daily oral hygiene routine, believing it helps maintain a healthy mouth. However, a recent study published in the Journal of Medical Microbiology in June reveals that some mouthwashes, particularly those containing alcohol, might be doing more harm than good.
The study, led by Dr. Christopher Kenyon of the Institute of Tropical Medicine in Antwerp and the University of Cape Town, found that regular use of alcohol-based mouthwashes, such as Listerine Cool Mint, was associated with increased levels of potentially harmful oral bacteria. The research involved 59 men who used either Listerine mouthwash or a placebo daily for three months. The results showed that those using the alcohol-based mouthwash had a higher prevalence of opportunistic bacteria linked to oral diseases and cancers.
Dr. Kenyon’s team discovered that alcohol and other antimicrobial agents in mouthwash are non-specific, meaning they not only kill harmful bacteria but also disrupt beneficial bacteria. This imbalance in the oral microbiome—an ecosystem of bacteria, fungi, viruses, and protozoans in the mouth—can create an environment where disease-causing bacteria thrive.
“We’ve found that when healthy individuals use products designed to kill bacteria, they often end up doing more harm than good,” said Dr. Kenyon. This follows previous research that suggested antibacterial mouthwashes might increase the risk of sexually transmitted infections by killing helpful bacteria.
In the current study, participants using Listerine Cool Mint mouthwash showed a significant increase in the bacteria Fusobacterium nucleatum and Streptococcus anginosus. The former has been linked to various cancers, including oral, esophageal, and colorectal, while the latter is associated with periodontal disease and possibly gastric cancer.
The findings are particularly relevant given the rise in head and neck cancers among younger adults, some of which are not linked to known causes like HPV infection or tobacco use. Experts like Dr. Joel Epstein, medical director of the cancer dentistry program at Cedars-Sinai, caution that while these results are intriguing, more research is needed to fully understand the relationship between mouthwash use and disease risk.
Despite the potential risks, mouthwash remains a common part of many people’s routines. However, experts advise that it is not essential for maintaining oral health. “Your microbiome provides crucial protection against infections and offers various other benefits,” Dr. Kenyon emphasized. “It’s better to avoid disrupting it with daily use of mouthwashes, particularly those containing alcohol.”
Dr. Epstein concurs, recommending that if mouthwash is used, it should be limited to short-term use under specific circumstances and should ideally avoid alcohol. Regular brushing and flossing remain the most effective ways to maintain oral hygiene.
As researchers continue to investigate the impact of mouthwash on oral health, it is clear that a balanced approach to oral care—emphasizing brushing, flossing, and careful use of mouthwash—may be the best strategy for maintaining overall health.
