Regular mouthwashes are a practical and popular method to protect the health of the oral cavity. Research shows that mouthwashes reduce the formation and spread of bacterial plaque between teeth and the risk of gingivitis (chronic inflammation of gums). They are also helpful for people treated for periodontal disease or periodontitis.
However, over the last 10-15 years, concerns have been rising about the usage of alcohol in these products. Most commercial brands use a certain amount of alcohol in their antiseptic solutions, and much research has now been pointing to the fact that there exists a possibility that regular use of alcohol-containing mouthwashes may be increasing the risk of oral cancer as well as cancer of larynx and pharynx which are located near oral cavity (the mouth).
The main issue in answering this question is that we lack long-term observational data. A lot of the evidence we have so far is of lower validity, so we need to be very careful with our interpretation.
As always, this article IS NOT meant to replace medical or dental advice. I am just sharing my attempt at interpreting the data. The advice of a dentist should ALWAYS be sought with priority.
In 2009 a review called “Are alcohol-containing mouthwashes safe?” was published in the British Journal of Medicine, where the authors concluded, based on the previously available evidence, that a possible association exists between the use of alcohol-containing mouthwashes and oral cancer, albeit very small. They also state that the evidence was conflicting and uncertain. They also said that there appears to be no difference between alcohol-containing and alcohol-free mouthwashes, so dental professionals could consider recommending alcohol-free solutions to patients.
Since 2009, more data has added up.
2020 Systematic review (Argemi et al.) pulled together 14 previously completed studies in an attempt to estimate the magnitude of the total results. Overall the studies included 21,466 people, of which about half were oral cancer patients. Three of the 14 studies were either in-vitro or in-vivo, not human studies. However, in a topic such as this, where robust human data is still missing, in-vitro research should not be ignored entirely.
The three clinical non-human studies show mutagenic and genotoxic changes in the samples of oral mucosa when exposed to alcohol-containing mouthwash (but again, these were NOT human studies); hence caution is required in the interpretation
Next, we have 11 case-control studies (note: case-control studies cannot infer causality. They need to be interpreted carefully. One of the main goals of case-control studies is to encourage research to invest future resources in prospective cohort studies, which have greater validity and more power in general) Of these only 5 explored the relationship between the two and no significant association was found. One might speculate that with more evidence the needle would be moved further to the right, however these were all case control studies which we need to bear in mind.
> One of the challenges remains that many smokers and regular alcohol drinkers use alcohol-containing mouthwashes multiple times a day to mask the unpleasant smell from other people. Not all studies control for alcohol intake & smoking.
> In this 2020 review (Ustrell-Borràs) alcohol types of mouthwash do not appear to be associated with oral cancer risk. Although looking at the forest plot for the five studies that considered alcohol content, we may see a non-significant trend towards harm rather than protection. More research might be needed to get more clarity here.
Source: (Argemi et al. 2020)
Another systematic review () from Spain looked precisely into the same topic. They pooled together eight studies that were all done on humans only. They were interested in seeing if aldehyde content in saliva increased the risk of cancer (aldehyde is a byproduct of alcohol metabolism)
The study concluded that while regular usage of alcohol-containing mouthwashes increases (temporarily) aldehyde concentration in saliva, there is no sufficient evidence to those that that in itself is associated with a higher risk of oral cancer
They also suggested (as previously stated) that the results of studies showing positive association might be confounded by the lack of control for alcohol drinkers and tobacco users who use alcohol-containing mouthwashes to mask the smell of alcohol/tobacco. In such cases, the cancer risk would result from smoking and drinking and not necessarily mouthwash usage.
A few smaller studies in this systematic review showed a positive association. However, not all of them were controlling for alcohol & smoking on the baseline.
And finally, a 2021 meta-analysis (Hostiuc et al) tried to look at the risk of oral, pharyngeal and laryngeal cancers (SCCHN) in alcohol-containing mouthwash users. They pooled together 17 human-based case-control studies (most of which were also analysed in the 2020 reviews above)
The most interesting finding was that using alcohol-containing mouthwash multiple times a day resulted in a marginal yet statistically significant 4% increase in upper aerodigestive tract cancer risk. (see below)
We do not know if this result might have been confounded by smoking or alcohol consumption
All other results showed no association between mouthwash usage
This study, same as all studies previously, is limited by the absence of more robust longitudinal data
SOURCE: Hostiuc et al 2021
CONCLUSION
Based on the available evidence today, it would be safe to say that the data remains inconclusive. There is insufficient evidence to indicate the pro-cancerous effects of alcohol-containing mouthwashes, but neither should the existence of such effects be discounted entirely in the absence of more robust longitudinal evidence.
A marginal yet statistically significant 4% increased risk of Oral, Pharyngeal and Laryngeal cancer association (Hostiuc et al. 2021) has been identified for those who used mouthwashes several times a day. This result was not seen in previous studies.
Regular use of alcohol-containing mouthwashes has been associated with higher aldehyde occurrence in saliva. However, no association between aldehyde content in saliva and oral cancer risk has yet been formed other than mechanistic speculation and reference to previously mentioned in-vitro data.
There are a few issues when trying to interpret this data.
There are currently no long-term prospective cohort studies which might help us answer this question. We only have case-control studies that are retrospective (looking at what already happened).
Most studies did not control for potential confounders such as smoking and alcohol consumption (many regular users of alcoholic mouthwashes do so to mask the unpleasant smell of tobacco or alcoholic drinks). In such studies, the risk of cancer could be induced by those rather than the mouthwash itself
Designing human clinical trials would pose a serious ethical concern hence it is unlikely that experimental data will ever be available.
The conflicting evidence warrants further research undertaken by a larger organization and more funding to be invested in prospective cohort studies. Members of the public would benefit from more clarity on this conundrum.
The known and proven benefits of these mouthwashes for dental disease prevention need to be weighted in and considered as well
The positive news is that for those concerned, there exists an alternative to using alcohol-free mouthwashes. In 2009 when the two types of mouthwashes were compared, they appeared to have very comparable effectiveness; hence using an alcohol-free solution appears as protective as its alcohol-containing counterpart.
People undergoing treatment for a periodontal disease or other condition should discuss making such switch with their dentist.
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NOTE:
This article does not constitute a medical or dental advice nor is it aiming to replace medical or dental advice where such advice is deemed appropriate.
References
Aceves Argemí R, González Navarro B, Ochoa García-Seisdedos P, Estrugo Devesa A, López-López J. Mouthwash With Alcohol and Oral Carcinogenesis: Systematic Review and Meta-analysis. J Evid Based Dent Pract. 2020 Jun;20(2):101407.
Hostiuc S, Ionescu IV, Drima E. Mouthwash Use and the Risk of Oral, Pharyngeal, and Laryngeal Cancer. A Meta-Analysis. Int J Environ Res Public Health. 2021 Aug 3;18(15):8215.
Ustrell-Borràs M, Traboulsi-Garet B, Gay-Escoda C. Alcohol-based mouthwash as a risk factor of oral cancer: A systematic review. Med Oral Patol Oral Cir Bucal. 2020 Jan 1;25(1)
Werner CW, Seymour RA. Are alcohol containing mouthwashes safe? Br Dent J. 2009 Nov 28;207(10):E19; discussion 488-9.