Smokers have been warned to stay away from mouthwash - as it might increase their risk of developing mouth cancer.
The combination of smoking and drinking alcohol has been established as increasing the risk of the disease.
Now researchers have warned that may apply even to alcohol in mouthwash.
The risk was examined by researchers led by dentist Dr John Reidy and colleagues in the Royal College of Surgeons and St James's Hospital in Dublin.
Around 400 new cases of oral cancer are diagnosed each year in Ireland, with two people a week dying from the disease.
Symptoms include red and white patches on the lining of the mouth or tongue, a mouth ulcer that does not heal or a swelling that lasts for over three weeks.
The most effective way of preventing mouth cancer is to quit smoking and limit consumption of alcohol, say experts.
The researchers said they were concerned about the effects the alcohol in the mouthwash had and it was therefore "prudent" to restrict their use by smokers.