Commonly used alcohol-based mouthwashes may have adverse effects on oral microbiomes -- the community of bacteria that live in the mouth -- raising risks of periodontal diseases and some cancers, according to a study.

The oral microbiome plays a role in digestion and keeps the mouth healthy.

The research, published in the Journal of Medical Microbiology, included men who have sex with men, who regularly use mouthwash as a method to reduce the transmission of sexually transmitted diseases.

Three months of daily use of the alcohol-based mouthwash increased the amount of two species of opportunistic bacteria -- Fusobacterium nucleatum and Streptococcus anginosus -- in the mouth of these men, said the team from the Institute of Tropical Medicine (ITM) in Antwerp, Belgium.

The two bacteria are known to raise the risk of gum disease, and oesophageal and colorectal cancers. Further, the researchers also observed a decrease in a bacteria group called Actinobacteria -- crucial for regulating blood pressure.

“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,” said Dr Jolein Laumen, from ITM’s Unit of Sexually Transmitted Infections. The researchers also called for larger studies to establish the risk.