Daily use of Listerine mouthwash may increase risk of bacteria linked to cancer, study claims

Overuse of Cool Mint Listerine is a cause for concern, say scientists - Patti McConville/Alamy

Listerine mouthwash may increase the risk of some cancers, a scientist has claimed.

Daily use of the Cool Mint flavour mouthwash was found in a recent study to increase the level of two bacteria in the mouth which have previously been linked with both esophageal and colorectal cancer.

It is thought that the alcohol in the product interferes with the normal level of bacteria in the mouth, known as the oral microbiome.

Two species of bacterium – Fusobacterium nucleatum and Streptococcus anginosus – were found to be much more abundant after three months of daily Listerine use.

Researchers also saw a decrease in a group of bacteria called Actinobacteria, which have previously been found to contribute to the regulation of blood pressure.

Scientists from the Institute of Tropical Medicine in Antwerp, Belgium, were investigating the impact of daily mouthwash use on STI risk in 59 gay men when they made the findings.

Participants used Listerine daily for three months followed by three months of placebo mouthwash or vice versa.

‘Most people should not be using it’

Study author Prof Chris Kenyon, head of the STI Unit at the university, told The Telegraph: “Both organisms can cause severe invasive infections and have been linked to various types of cancer, such as esophageal and colorectal cancer.”

Daily mouthwash use “could increase their risk of cancer and various infections”, he claimed.

“Most people should not be using it and if they do use it, they should use the preparations without alcohol and limit the use to a couple of days.”

Listerine is one of the most recognisable oral care brands in the world and Cool Mint is its trademark blue product. The company is owned by Kenvue.

Prof 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.

Listerine is around 20 per cent alcohol but alcohol-free alternatives do exist and are recommended by the scientists of the latest study.

“Listerine use was associated with an increased abundance of common oral opportunistic bacteria previously reported to be enriched in periodontal diseases, esophageal and colorectal cancer, and systemic diseases,” the authors write in the paper, published in the Journal of Medical Microbiology.

‘Be guided by healthcare professionals’

“These findings suggest that the regular use of Listerine mouthwash should be carefully considered.”

Dr 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.”

Information on dietary habits and smoking were not collected so researchers were unable to account for these in the results.

A spokesman from Kenvue said: “Kenvue welcomes and encourages scientific advancements and exchanges to promote everyday health.

“Based on our initial review, the published trial lacks several important design controls and adequate rigour to make any conclusions about potential impact to human health.”

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