Daily use of Listerine mouthwash linked to bacteria that may increase risk of deadly cancers in shock study

For the study, conducted at the Institute of Tropical Medicine in Antwerp, Belgium, the researchers investigated the impact of daily mouthwash use on STI risk among gay men.

They specifically set out to find ways of reducing the incidence of gonorrhea, chlamydia, or syphilis in men who have sex with men.

The 59 participants enrolled in the study used Listerine daily for three months followed by three months of placebo mouthwash or vice versa.

The researchers found a significant difference in the composition and number of bacteria in the participants’ oral microbiome after using alcohol-based Listerine Cool Mint mouthwash.

They reported that fusobacterium nucleatum and streptococcus anginosus were significantly abundant after using the mouthwash daily.

These two species of bacteria have been linked to several diseases, including gum disease and esophageal and colorectal cancer.

The scientists also noted a decrease in a beneficial bacteria strain called Actinobacteria. This strain of bacteria regulates blood pressure and is thought to have potent anti-cancer properties.

There are some important limitations to the study.

The researchers did not collect information on the participants’ dietary habits or smoking. It is therefore not possible isolate a single factor that may contributed to the risk of cancer.

Other imitations included:

• Swabs of areas of the mouth were limited to tonsillar pillars and the posterior oropharynx. The authors note that the results may not represent the entire oral cavity.
• Adherence to using the mouthwash was not controlled.
• Changes were not confirmed with a second methodology.
• Only men who have sex with men were included in the study. Therefore, the results might not be generalisable to the general public.

LATEST DEVELOPMENTS

• Urgent health warning after THIRD company recalls product over E. coli fears
• Bowel cancer breakthrough as tumours shrink in patients
• Scientists discover new symptom of dementia

With these uncertainties in mind, the researchers are unwilling to state that the public should stop using alcohol-based mouthwash altogether.

Instead, they recommend exercising caution and careful consideration over the regular use of Listerine.

Study author Professor Kenyon and his colleagues only tested Listerine but he says the impact on bacteria would likely also be seen following use of other alcohol-based mouthwashes.

Doctor Jolein Laumen, first author of the study, added: “Alcohol-based mouthwashes are widely available. The public may use them daily to tackle bad breath or prevent periodontitis, but they should be aware of the potential implications.

“Ideally, long-term usage should be guided by healthcare professionals.”

In response to a request for comment, Kenvue, which owns the Listerine brand, told GB News: "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 oral mouthwash brands in the world. We continuously evaluate the latest science. There is no evidence that LISTERINE^® causes cancer."

What might explain this link?

We’ve known for a long time now that alcohol increases the risk of mouth cancer, and it’s not a particularly new concept.

So the idea that using mouthwash that contains alcohol could increase the risk of mouth cancer does make sense, but the evidence around this link is inconsistent, and the link to esophageal and colorectal cancer is even less clear. To date, no direct link has been established.

According to Alliance Dental, most mouthwashes found in pharmacies contain alcohol.

The alcohol destroys almost all the bacteria in the mouth — both the good and the bad.

Alcohol-free mouthwash does not destroy all the bacteria but creates a new balance of bacteria in the mouth.

This might have contributed to the risk but again more research needs to be done before conclusions can be drawn.

As Cancer Research UK rightly points out, the most important risk factors for mouth cancer are smoking and drinking more than three units of alcohol a day.