Student guest post by Francis Mawanda

If you are like me, you probably always and almost faithfully, include a bottle of mouthwash on your grocery list especially after watching and/or listening to the numerous commercials in the media which claim that you will not only get long lasting fresh breath, but also freedom from the germs that cause plaque and gingivitis. However, many proprietary mouthwashes including my favorite brand contain Alcohol (ethanol) which also gives them the characteristic burn we have to endure, albeit for a few seconds each day, but safe in the knowledge that the product is hard at work killing all the germs that give us bad breath and may cause plaque and gingivitis. But the question I continually ask myself is whether regular or long term use of these products is safe especially after reading the numerous research reports and newspaper articles suggesting a possible link between long term use of alcohol based mouthwashes and oral cancer.

Several research studies have reported finding an association between long term mouthwash use and oral cancer (1, 2, 3). For example, in a study conducted by Wynder and colleagues (1), they found a significant association between mouthwash use and oral cancer. A bigger multi-site study by Guha and colleagues (3) comparing participants who reported having used mouthwash to those who reported never having used mouthwash found that individuals who reported using mouthwash more than twice a day were nearly six times more likely to develop oral squamous cell carcinoma compared to those who reported never having used mouthwash. However, in both these studies, no distinction was made on whether participants used alcohol or non-alcohol based mouthwashes which raises several epidemiological concerns such as specificity, since not all mouthwashes contain the same chemical ingredients

However, several studies have been conducted in which a distinction was made between alcohol containing and non alcohol containing mouthwash use (4, 5, 6). Unfortunately, these studies have produced mixed results. While some studies reported finding a positive association between alcohol containing mouthwash use and oral cancer (4), other studies found no association at all (5, 6). For example, although a 1983 study conducted in the states of California, Atlanta, and New Jersey by Winn and colleagues (4) found an increased risk of oral cancer among users of alcohol containing mouthwash compared to both non-users and users of non-alcohol based mouthwash, a similar study conducted in Puerto Rico found no significant association between the use of alcohol based mouthwash and oral cancer.

To add to the confusion is the fact that reviews of the subject by epidemiologists and other experts have also produced mixed results. While some researchers in their reviews concluded that the results of these studies provide sufficient evidence to demonstrate a link between long term use of alcohol based mouthwash and oral cancer (7, 8), other researchers concluded that the evidence is not sufficient to make the conclusion that there is an association between alcohol based mouthwash use and oral cancer (9,10).

Furthermore, while systematic reviews or meta-analyses can give us a better picture of the association between use of alcohol based mouthwashes and oral cancer because they can generate a pooled risk estimate by aggregating all the findings on the subject, there has only been one meta-analysis on this subject which was conducted by epidemiologists in Europe (10) and concluded that there is no excess risk for oral cancer from use of alcohol or non-alcohol based mouthwash.

From all this confusion, it’s clear that a randomized control trial (RCT) is needed to determine with a higher degree of certainty whether there is a true association between long term use of alcohol based mouthwashes and oral cancer. However a RCT is not feasible in this case simply because it would be unethical to expose individuals to a product that may cause cancer however weak the association maybe. Possible alternatives include quasi-experimental studies, prospective cohort studies or repeated case-control studies which may provide sufficient evidence through consistency. However, results from these alternatives will still face criticism since they do not offer unbiased estimates.

Therefore, until concrete evidence is available, the decisions on whether to use mouthwash or not and whether to use alcohol based or non-alcohol based mouthwashes remains a matter of personal preference and of course cost for some of us.

References

1. Weaver A, Fleming SM, Smith DB. Mouthwash and oral cancer: carcinogen or coincidence? Journal of Oral Surgery 1979;37:250-3.

2. Wynder E L, Kabat G, Rosenberg S, Levenstein M.Oral cancer and mouthwash use. J National Cancer Institute 1983; 70: 255-260.

3. Guha N, Boffetta P, Wunsch Filho V et al. Oral health and risk of squamous cell carcinoma of the head and neck and oesophagus: results of two multicentric case-control studies. American Journal of Epidemiology 2007; 166: 1159-1173.

4. Winn D M, Blot W J, McLaughlin J K et al. Mouthwash use and oral conditions in the risk of oral and pharyngeal cancer. Cancer Research 1991; 51: 3044-3047.

5. Winn D M, Diehl S R, Brown L M et al. Mouthwash in the etiology of oral cancer in Puerto Rico. Cancer Causes Control 2001; 12: 419-429.

6. Marshberg A, Barsa P, Grossman M L. A study of the relationship between mouthwash use and oral and pharyngeal cancer. Journal of the American Dental Association 1985; 110: 731-734.

7. McCullough M J, Farah C S. The role of alcohol in oral carcinogenesis with particular reference to alcohol-containing mouthwashes. Aust Dent J 2008; 53: 302-305

8. Werner C .W. & Seymour, R. A., Are alcohol containing mouthwashes safe? British Dental Journal 2009; 207: E19

9. La Vecchia C. Mouthwash and oral cancer risk: an update. Oral Oncology 2009; 45: 198-200.

10. Lewis M A O, Murray S. Safety of alcohol-containing mouthwashes. A review of the evidence. Dent Health (London) 2006; 45: 2-4.

Comments

  1. #1 Markk
    April 23, 2010

    I hope these studies take smoking into account otherwise they are worthless.
    It is unlikely to be the ethanol anyway, or whole bunch of drinkers who drink more than one would be affected. Or perhaps that is true…

  2. #2 DizzyDMD
    April 23, 2010

    I recall one such Australian study that provoked this…

    When you’re looking at oral cancer rates (I’ve seen it myself 3 times in my 4 years of practice) – you need to see what all the other factors are. With these studies – are they differentiating between other lifestyle habits that contribute to oral cancer? Smokers have higher oral cancer rates than non-smokers, and smokers and ‘casual’ alcoholic drinkers much higher than that. Smokers tend to use mouth rinses more often than non-smokers to begin with.

    I haven’t read these studies yet – but are they differentiating the patient pools as such, considering that the risks of oral cancer between these groups are variable in themselves?

  3. #3 DizzyDMD
    April 23, 2010

    http://www.cda-adc.ca/jcda/vol-75/issue-4/260.pdf

    A relevant paper published in the JCDA regarding this topic (don’t worry, it’s an easy read)

  4. #4 Colin
    April 23, 2010

    Yeah, but *why* do the people use mouthwash? If it’s for halitosis then maybe the underlying cause of that is the cause of oral cancer and not the mouthwash.

  5. #5 Cheryl
    April 28, 2010

    My husband developed tongue cancer in 2007. He did not drink or smoke. He did however, use Listerine twice a day for over 30 years. The oral surgeon suggested that the mouthwash or how it is properly refered to “alchol caontaing mouthwash” could have been the cause. My husband died, June of 2009 a from the cancer. It was the worst thing that I have ever seen.

  6. #6 Lewis Larson
    April 28, 2010

    Of course there are many studies showing people who smoke and drink alcohol have a much higher chances of having oral cancer. Connect the dots!!!!!!!!!!!!!

    I am an experienced Periodontist

  7. #7 Nathan
    June 27, 2010

    I’m having trouble of remembering where I read this, but one piece suggested that the prolonged presence of alcohol in the mouth (excessive drinking, usage of mouthwash in this case) may result in oral cancer.

    Of course, like this article says, the nature of the problem makes a real answer tough. A start would be to make sure to exclude any other factors that might lead to oral cancer (use of tobacco, for exampmle).

    So I don’t know…

  8. #8 Paul Guiver
    November 1, 2010

    I am a non-smoker and drink occasionally but not heavy (Beer and wine with meals).
    I note from ‘Colin’ in Comment #4 states people possibly use mouthwash for ‘halitosis’! Actually, I had major dental work 7 years ago as a result of a car accident when I was younger. I have since then have used Corsodyl religiously twice a day (recommended by Military Dentists) to keep my gums healthy and free from infection. I have health gums but now I have squamous cell carcinoma cancer on my tongue; diagnosed from the biopsy after a 5 hour operation (Neck dissection) to remove secondary tumours in my neck lymph nodes.
    I now intend to conduct my own research into the effects of gargling ethanol!
    What would it cost the producers of Mouthwashes containing alcohol to place a simple warning/statement on the bottle? If further research is proven it will cost them a hell of a lot more….

  9. #9 Charisse
    December 9, 2010

    Just a warning about the link to a relevant paper on this topic shared by DizzyDMD: http://www.cda-adc.ca/jcda/vol-75/issue-4/260.pdf.

    According to the article, the author, Dr. Iacopino, is a consultant to Johnson and Johnson, the manufacturer of Listerine, and is also consultant to other dental companies. This makes me weary of taking the article seriously. I am not trying to question this professional’s integrity; I would, however, like to see the same thing written by an independent company.

  10. #10 Isaias
    February 18, 2011

    I agree, there are so many other important factors that need to be taken into consideration when testing for cancer causing catalyst. The number one, as stated previously would be smoking and drinking, however now with the arrival of electronic cigarettes this may not be so much of a concern. I think all industries need to have a common goal of reducing cancer causing agents such as those found in many common plastic packages and foods. That in conjunction with reduced pollution and continued research into fields such as e-cigs will reduce cancer risks – and therefore the death rate- significantly.