Does mouthwash cause cancer?

Article reviewed in October 2020. There is still no credible evidence linking mouthwash usage to oral cancers. For more information, read this piece from the NHS.

The latest cancer scare story to hit the headlines this week was about mouthwash.  An Australian researcher claimed to have found ‘sufficient evidence’ of a link between alcohol in mouthwashes and mouth cancer.

He even went on to suggest that ‘it is inadvisable for oral healthcare professionals to recommend the long-term use of alcohol-containing mouthwashes’.

Now, most people reading the story may feel the need to run home and clear their bathroom shelves. But hold on, don’t pour your bottle of mouthwash down the sink just yet. Let’s take a look at what the evidence says.

What do we know?

We’ve known for a long time now that alcohol increases the risk of mouth cancer, and it’s not a particularly new concept. So the idea that using mouthwash that contains alcohol could increase the risk of mouth cancer does make sense, but the evidence around this link is inconsistent.  Scientists have looked at this many times before, and found that there is no real evidence to suggest that using mouthwash can increase the risk of mouth cancer.

So where’s the ‘sufficient’ evidence?

Let’s take a closer look at how the researcher came to find ‘sufficient evidence’ for this link.  This new Australian study is actually a review of the existing evidence, although similar reviews in the recent past have concluded that there is not enough evidence for a link between alcohol-containing mouthwash and cancer.

This new review places a lot of emphasis on a large study carried out in Latin America and Central Europe in 2007.  The study looked at the link between many elements of oral hygiene and mouth cancer. The investigation of a link between mouthwash use and mouth cancer formed only a small part of the study.

Although the findings did suggest that mouthwash use may increase the risk of mouth cancer, the researchers warned that their findings should be ‘interpreted with caution’, largely because they did not record the alcohol content of the mouthwash, the length of time that people had used mouthwash, or how long they held it in their mouth. The researchers on the Latin American and Central European study conclude that ‘the alcohol content of certain mouthwashes may be a causal agent’ for mouth cancer.  This is not the same as there being ‘sufficient’ evidence.

When scientists talk about having sufficient evidence, we would expect to find lots of studies that are saying the same thing and that can explain why there might be a link.  In this case, although we can see why there might be a link, the research is not telling us the same thing. There are only a small number of studies and they largely disagree. The evidence about mouthwash and mouth cancer is not consistent let alone ‘sufficient’.

The point is…

Despite what the Australian study claims, there is still not enough evidence to suggest that using mouthwash that contains alcohol will increase the risk of mouth cancer.  The most important risk factors for mouth cancer are smoking and drinking more than three units of alcohol a day.

Yinka Ebo is a health information officer at Cancer Research UK