LISTERINE mouthwash disrupts oral microbiome in men

Iveta Ramonaite, Dental Tribune International

Tue. 2. July 2024

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ANTWERP, Belgium: Research has found conflicting results regarding whether the popular bactericidal mouthwash LISTERINE promotes or undermines a healthy oral microbiome. Seeking to shed light on the issue, a recent study has reported a significant alteration in the composition and abundance of bacteria in the participants’ oral microbiome after using the mouthwash, and this may lead to various oral and general health issues.

The research was part of the Preventing Resistance in Gonorrhoea trial and investigated the use of mouthwash to reduce the transmission of sexually transmitted diseases in men who have sex with men (MSM) and who are taking HIV pre-exposure prophylaxis. “In the original randomised controlled trial, we found that the daily use of LISTERINE COOL MINT led to an increased incidence of pharyngeal gonorrhoea. We hypothesised that this was due to LISTERINE COOL MINT’s deleterious effect on the microbiome, which protects people against infections such as gonorrhoea,” senior author Prof. Chris Kenyon, head of the Sexually Transmitted Infections Unit at the Institute of Tropical Medicine in Antwerp, told Dental Tribune International.

In the study, the researchers recruited 59 MSM taking HIV pre-exposure prophylaxis to examine whether the alcohol-based LISTERINE COOL MINT had an impact on their oral microbiome. For that purpose, the participants used LISTERINE daily for three months, followed by a placebo mouthwash for three months, or vice versa. Oropharyngeal swabs were taken at baseline and after the use of each mouthwash for three months.

The researchers discovered that the opportunistic bacteria Fusobacterium nucleatum and Streptococcus anginosus, which have been previously linked to periodontal disease and to oesophageal and colorectal cancers, were significantly more abundant in the mouths of the LISTERINE users after three months of use. Additionally, LISTERINE use led to a decrease in Actinobacteria, which are responsible for regulating blood pressure.

Discussing the results, lead author Dr Jolein Laumen, a researcher at the Sexually Transmitted Infections Unit, said in a press release: “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.”

According to Prof. Kenyon, up to half of MSM report using mouthwash for oral hygiene. In light of the findings, he believes that the present study offers evidence that this might disturb their oral microbiome.

Since factors such as the participants’ dietary habits and smoking were not accounted for and the study included only a small sample group, the results are not representative of the entire population. Further research should examine how the detected changes affect clinical outcomes in larger and more representative sample groups.

The study, titled “The effect of daily usage of Listerine Cool Mint mouthwash on the oropharyngeal microbiome: A substudy of the PReGo trial”, was published online on 4 June 2024 in the Journal of Medical Microbiology.