What's That Rash? - Mouthwash: good or bad for you?

0:00ABC Listen. Podcasts, radio, news, music, and more. There are a lot of perfectly sensible reasons to start a war. Territory, resources, pigs. Wait, what? You've got to pay for that pig. Yes, a pig, a pastry shop, a football game, sometimes even birds. They don't seem to be easy to kill. History is filled with some stupid wars. On the No One Saw It Coming podcast, we are diving right into them. With me, Mark Finnell.

0:32Search, no one saw it coming podcast on ABC Listen, or wherever you get your podcasts. Norman, I know more about your oral hygiene habits than I do about most people in my life. I know that you do... Declaration only from a distance. Only from a distance. But I know about your interdental cleaning habits. I know that you won't share a toothbrush with another human, but you don't mind if a cockroach crawls over the top of it. But I don't know whether or not you're a mouthwash guy.

1:01I'm not really. I mean, I'll tell you what I do do mouthwash for is I've got the European habit that if I've had an espresso or a coffee, I will have a glass of water and sort of rinse my mouth and swallow afterwards just to prevent staining, which is what the Europeans do. But I don't use mouthwash, but I try and keep the toothpaste in my mouth for as long as possible. But that's for another story and we'll have a link to our delving into my terrible toothbrush habits on our show notes.

1:29Well, mouthwash is the topic today. Maybe I'll change your mind in this chat, Norman, because we've got lots of questions about mouthwash today on What's That Rash? That's the show where we answer the health questions that simply everyone is asking. Now, when we have so many questions about mouthwash, three different questions today, and they're not all the same question, which I actually find is really interesting.

1:54Chris says, I was wondering whether you had any thoughts on the effectiveness of mouthwash. Oral care is certainly very important. You've addressed this in previous episodes. Chris says, I brush floss, use interdental brushes and mouthwash regularly. But I was wondering if there was any additional benefit in using a commercial mouthwash, of which there are many.

2:14Paul says, my wife has read somewhere on the internet that mouthwash kills the good bacteria in your mouth as well as the bad. Does your mouth actually have a microbiome worth protecting or is the bad bacteria from food infinitely worse? And that says, hey, Team Rash, can you please provide some comment on one of your shows about the regular use of mouthwash having an adverse impact on the body, including the increase of blood pressure?

2:42There is so much in here, Norman. We've got a lot to cover today. It's a lot. So let's rinse and move. Rinse and repeat. I guess we can start with mouthwash as a concept. It's pretty, like it's very, very old. The idea of rinsing your mouth out for oral hygiene reasons, very, very old. What sort of things do you think people have rinsed their mouths out with over the years, Norman? Okay. I'm sorry I had some avocado on toast before I came in because you're about to tell us.

3:11There's an ancient Chinese medical text from about maybe 2600 BC that advises treating gingivitis or periodontis with the urine of a child. As a mouthwash. As a mouthwash. Well look, there were plenty of parents listening who probably tried that when they were changing a nappy with a male child. By accident. Yeah. So could you write in if after your child was born and you were a little boy?

3:41You had less need for the dentist. It was really interesting to hear. I'm very glad to say I cannot relate. But yeah, if you've got that story, we want to hear it. Our email address is that rash at abc.net.au. The ancient Chinese also had some more familiar mouth rinses, salt water, a big one. It's ancient tea and wine because they have antiseptic properties.

4:05Hippocrates, it's pretty hard to talk about ancient medicine without mentioning Hippocrates. He said a mixture of salt, alum and vinegar, which again, not unfamiliar sort of gargles. No, vinegar has an antibacterial effect. Yeah, and salt water. I mean, even now, if you have dental surgery, they'll often recommend salt gargles to help.

4:27keep your mouth healthy and sort of ward off bacteria. And it was also common practice in the Americas. So there was through North America and Mesoamerica, mouthwashers, including from a plant called Coptus trifolia, which is related to renunculus. And so it looks a bit like parsley, but they would make a saltwater mouthwash or they'd use this sort of herbal mouthwash. So even before we had a sense of microbes causing dental problems or oral problems, mouthwashes have been around for literally millennia. But the first science really emerged in the 17th century with the person who, well did he invent the microscope? He certainly started using the microscope to study microorganisms, Anton Van Leeuwenhoek.

5:13I'm glad you said his name, Norman, because I was a bit scared of that Dutch name. But yeah, he lived near Delft, so on the water, and was looking at the water through his microscope, saw microorganisms in the water and looked at adding different substances to the water to see what this did.

5:29to these moving microbes in the water. Vinegar and brandy both immobilised or killed the organisms in the water and then he tried doing the same sort of thing with the mouth so he did it with his own mouth and somebody else basically gave them a mouthwash containing vinegar or brandy but found that there still were living organisms in the dental plaque and so there was this sense of okay we have some substances that can kill microbes but in the mouth they're sort of were able to hide and then the hunt was on for something that would actually manage to sort of find its way in.

6:07in a durable enough way to kill those microbes. And they found it in the form of chlorhexidine, not live and hope. This is some years later in the 1960s. Just one or two years later. A couple of centuries later, Harold Lowe in Denmark demonstrated that chlorhexidine could help prevent the buildup of dental plaque. We still use chlorhexidine today in mouthwashers. It's also like a hospital antiseptic. It's a really important antiseptic these days. So I mean, all that to say, we now have all sorts of commercial mouthwashers.

6:36on the market. They are all building on these centuries of research. The question is, really, what do they do in the mouth? And then, yeah, as Matt and Paul's questions are, do they have side effects as well? Yes. So look a little bit of the basics here. You acquire the microbiome in the mouth quite early on in life from your mother.

6:59or indeed your family. So if you're using a pacifier and you lick the pacifier when you pick it up off the floor, which is what you should not do, you are transferring your microbiome to the mouth of the baby. And that can transfer what are called karyogenic bacteria to the mouth.

7:14So promoting dental caries as in life. So you can acquire that very early on in life, but they're all in microbiome and that's what, you know, if you eat sugary foods that feeds those bacteria and then they form this very sticky plaque on your teeth which then erodes the teeth and the form of dental decay. Really one of the common infectious diseases we suffer from and and often unpublicized or under publicized side effect of eating too much sugar and you're dying too much refined carbohydrate. So the oral microbiome though is much more complex than that. So there are bacteria, there are fungi, there are archaea which are very ancient forms of microorganisms which are not fully understood.

8:00and viruses. So there's a very rich microbiome and it's said that the microbiome changes in the mouth according to where you take it from. So the gums seem to have a microbiome of their own as well as the general mouth and teeth and so on. We already spoken about plaque. That's crazy. So even within your mouth there are different like neighborhoods with different populations. It seems so. And at its core you want as healthy a microbiome as possible. And it looks as though the microbiome in the mouth is different from the microbiome in the gut or the microbiome in the skin. So it's a very specific environment. And people have related the health of the mouth to the health of other organs, particularly the brain, but we'll come back to that later. It's funny you say the babies sort of developed that mouth microbiome.

8:46in early life and they get it from their mums and stuff like that. But I just think about the fact that babies are just determined to put every single thing they encounter into their mouth. Like they are actively populating that oral microbiome from basically about four or five months onwards. Yes. And of course, it's another reason why when you start feeding solids to babies and then they progress through the first year of life that around about the age of 12 months, you should be giving them a modified adult diet, not rubbish like toddler milk.

9:16You want to be eating a normal diet and of course every what's that rash parent is eating a very healthy diet which encourages a diverse microbiome. Need I say what it's called? Well you know what I left my bell on my desk and I don't know why I keep doing that because honestly it comes up every time. We are of course talking about the Mediterranean diet. Very important for your gut microbiome but yeah now I'm learning for my oral microbiome as well.

9:41So then it comes to teeth washing and we've done lots on teeth washing so it's good for you. So is interdental brushing, so is interdental taping, what do you call it? Flossing. Flossing, that's the word. Interdental taping. The questions that we've got are around mouthwash. Does adding mouthwash make a difference and what might be the side effects? Well, this has been studied. There have been quite a few research papers looking at exactly this. And they don't all necessarily agree.

10:08I mean what they do agree on is that mouthwash with say chlorhexidine or equivalent antiseptic and chlorhexidine has been the best studied can actually slow the development of dental plaque. But there are ifs and buts about that.

10:23Well, the first thing I want to ask is how much additional benefit if you're already, so Chris's question, right? Chris says, I brush, I floss, I use interdental brushes. If you're then layering mouthwash on top of that, are you actually getting much additional benefit if you're already taking quite thorough care of your teeth and gums? Well, you might be reducing the benefit depending on the mouthwash that you use. Reducing the benefit? Yes. So Chris is doing the right stuff. So he's cleaning out the mouth. Maybe he's...

10:51keeping the toothpaste if he's listening to what's that rash in his mouth while he does all that work and then spitting it out. But not rinsing. But not rinsing. Now if you then mouthwash after that and the mouthwash does not contain a lot of fluoride then you could be losing the fluoride that you've gained from the toothpaste. So there are two solutions to that if you really want to use at the end of what's this what's that rash you really want to use. Mouthwash is Ideally, you want to use a fluoride-containing mouthwash, but ideally, you do not want to use the mouthwash at the same time as you wash your teeth. So you wash your teeth, and then maybe later on in the day, you would use your mouthwash as a top-up of the fluoride, but don't risk losing the effect of the toothpaste. So non-fluoride-containing mouthwash, the debate is just how long that effect lasts on dental plaque, because fluoride...

11:45is really the secret sauce when it comes to maintaining dental health. But that's your teeth. Like you said, the oral microbiome is many and varied and there's more to your mouth than just the teeth in it. Is there maybe something happening with your gums and your tongue and your cheeks with mouthwash that is beneficial? So there are clinical benefits for some conditions that your dentist might recommend it for.

12:07antiseptic mouthwash has been shown to be a benefit in gingivitis, so inflammation of the gums around the margins. And if your dentist recommends it, we are certainly not going to contradict that. That has been shown to be of benefit. But in other areas, less so.

12:22So that's kind of Chris's question. Am I getting an additional benefit from the mouthwash? It sounds like it's marginal, maybe even detrimental if they're washing the fluoride off their teeth at the time. But Paul's question was about the microbiome. We know that mouthwash is killing bacteria. What do we know about its maybe detrimental effects on the good bacteria that might be in our mouths? We don't know is the short answer. There have been studies, but they've been small and a bit fragmented.

12:49So we simply don't know the effect of this antiseptic in the mouth. And it's likely that it is changing the microbiome from its healthy state, as well as preventing dental plaque. So the oral microbiome, because of its specificity, has been associated with other conditions. Now, this research is also not terrific. But for example, there is thought to be a relationship with perhaps even Alzheimer's disease or dementia.

13:18that the messaging from the mouth to the brain, because it's nearby, from the oral microbiome, might actually influence brain health. The evidence for that is not terrific, but there's some evidence on autoimmune disease and the oral microbiome. So you're fiddling around with, if you're eating a healthy diet, fermented foods and so on, and you are doing the basics, which is not eating a lot of sugar and getting rid of the plaque as much as possible.

13:44then it is possible you might be doing some harm. Now here's the other one because we've got a question about high blood pressure from that. Yes, I'm fascinated by what this link could possibly be. So there is some evidence that a healthy oral microbiome produces nitric oxide. And nitric oxide is a substance that dilates blood vessels and is associated with cardiovascular health. And that when you get rid of a healthy microbiome, you lose these nitric oxide producing organisms and maybe have a detrimental effect on the cardiovascular system. Nitric oxide dilates blood vessels, dilates the arteries. And if you get constriction of the arteries, which is what you might get, if you have an absence or a lower level of nitric oxide, remember it's a very short lived substance in the body. So take this with the...

14:35pinch of fluoride, you might get constriction and when you get constriction of blood vessels that's when you can get high blood pressure. So there is a little bit of a relationship between a restricted oral microbiome and high blood pressure which might be related to mouthwashes. Not strong. It must be minuscule amounts that we're talking about here. How could that possibly have a meaningful change to your blood pressure when we're just talking about a couple of tiny bacteria in your mouth. It must be transient, right? Like it's, you're eating food, it's passing through, or you're rinsing your mouth and it's passing through. How big could this effect be? Good question. But we're not talking about one or two bacteria. We're talking about millions and millions and millions of bacteria in your mouth, which are there all the time, churning away, producing nitric oxide. So it's conceivable, but even then the amounts may well be quite low.

15:28And so, you know, I'm not making a big deal of this. There is some evidence, but it's not strong. It has been related specifically to chlorhexidine. But that's probably because chlorhexidine is the commonest antiseptic. And therefore, if you're doing a study of this, most people have used chlorhexidine in their mouth washes. And it may well be that in people who might be teetering on the edge of high blood pressure, it's enough to tip them over. Who knows?

15:51It is hard with studying. Mouthwashers have a big catchall term for lots of different things. Some of them are like herbal. Like you said before, Chlohexidine is an ingredient in a lot of them, but not all of them fluoride sometimes in them. Sometimes it's not. Essential oil. Yeah, exactly. It's quite hard to generalize. You're talking about high blood pressure. There is a study from Finland which correlates gut oral health with a reduction in the risk of heart disease, particularly dying of heart disease by as much as 51%.

16:20But the mouthwash didn't have an additional effect on this benefit. And the theory here is that if you've got an unhealthy oral microbiome, a lot of dental plaque and inflammation in your glums, that inflammation spreads to your body and can affect your cardiovascular system, increasing the risk of heart attacks and strokes. So oral health is linked to cardiovascular disease like the question was from...

16:43Matt. But mouthwash wasn't going to make a difference. Everything is interconnected, especially in the mouth Norman. And we did actually do an episode on flossing where we talked a little bit about this link. So if people want to listen to that as well, they can go back through the WhatsApp Rash feed. One more thing, this wasn't specifically asked by our question askers, Chris, Paul and Matt, but there was a bit of a worry a couple of years ago on the internet that maybe using mouthwash affected your risk of oral cancer. What do we know there?

17:11The evidence is really mixed about oral cancer and mouthwashers because in years gone by people would have used oral mouthwashers. When there were smokers, when there were more smokers around to stop tooth staining, maybe to change the smell of their breath to get tobacco off their breath and so on. And smoking causes oral cancer. So it could be that the oral mouthwash was not causing the cancer. It was the smoking. It was just that smokers use more mouthwash. That was the other thing. People wondered whether it was alcohol in mouthwash. So a lot of manufacturers removed alcohol or reduced the amount of alcohol in mouthwashes.

17:45But when you look at the core evidence, it's not convincing that there is a strong risk of oral cancer. So Chris, Paul, Matt, bottom line, are we encouraging mouthwash, are we discouraging mouthwash, or are we neutral on mouthwash norman? Well, what do you think? I feel like we're neutral. And I think that there's probably reasons why some people might need some help with plaque removal if.

18:08toothbrushing and dental flossing isn't an option for them maybe for mobility reasons or that sort of thing but I am suspecting based on our chat that there isn't much additional benefit of mouthwash if you're already very fastidious with your oral health and could possibly cause a little bit of an undermining of what you're trying to do. How'd I go?

18:29Pretty good. I agree with that. And I'm certainly not going to start using mouthwash. I just don't know what you're playing with there. I'd much rather do things the way I have been doing and continue along those lines. Well, your pearly whites are testament to your excellent oral hygiene. Chris, Paul, Matt, thank you so much for your questions. We hope this has been useful. Our email address, if you want to ask a question, is thatrash at abc.net.au. It is also where you can send us any feedback you have about the topics we discuss.

18:58So what's in the mailbag? Well, we spoke the other day about continuous glucose monitoring, the little button on the back of your tricep that people can use if they're interested in their glucose behaviour over the day, designed for people with diabetes to use. Anyway.

19:13James has emailed in. A lot of people without diabetes using it. Exactly, which is what we were talking about. Well, James has emailed in to say, I listened to your recent episode about CGMs, continuous glucose monitors, with interest and excitement as I realized I finally have an end of one experiment to share with you. And for all new Watch That Rash listeners, an end of one study which we love on Watch That Rash is you're doing an experiment on yourself.

19:37We love them for anecdote reasons, but look, it's not the most scientifically robust type of study, but it is a very fun type of study. And we salute all these self-experimenters out there. Indeed. Well, James says my average blood glucose for many years hovered around 5.7, which is close to the prediabetic range. However, my fasting glucose and a glucose tolerance test has always been normal.

20:01Given my otherwise normal markers and generally obsessively healthy lifestyle, my GP has never been too worried. Nevertheless, a couple of years ago, I thought I'd do some more investigation of my own and signed up for a CGM subscription. After a few days of wearing it, James says, I noticed quite large spikes after eating.

20:20Thankfully, these went down after a couple of hours, but the magnitude and slope of the spikes were a bit concerning. Not completely trusting this thing, I invested in a finger prick glucose monitor and thought I would compare the two. This is real commitment here. Absolutely. I decided to sacrifice my fingertip for science and spent a pleasant afternoon slash evening taking finger prick measurements every 15 minutes and recording them alongside the CGM reading. You're a gift for medical science.

20:50The CGM lagged behind the fingerprint monitor slightly, which is apparently to be expected given that one measures interstitial glucose while the other measures blood. We should explain what that is. That's glucose in the tissues just under your skin.

21:03Right and the other measures blood glucose directly. What was really interesting however was that the relationship between the two was not linear. The CGM was always higher than the finger prick monitor with the measurements a lot closer at low values and further apart at higher measurements. The upshot of this is that the CGM graph looks a lot more sinister and a finger prick graph is a lot flatter. James has sent us his graphs.

21:33I can't imagine having this level of commitment to a bit, honestly. Yeah, hats off, James. This is great. Anyway, James says, my conclusion from this is that I'm probably fine. It's possible the fingerprint monitor was inaccurate. However, it suits me to believe it rather than the CGM. Also, I had my average glucose measurement re-measured at the start of this year. It was down to 5.5, possibly as a result of pushing some bigger weights in the gym and putting on a bit of muscle.

22:00There you are, James. A testament to not bothering to wear a CGM if you're otherwise healthy. And we did talk a little bit about the danger of getting into obsessive territory if you do go on these monitors. James, I don't know how you feel, but it certainly appears that there may be a risk. So hopefully you're doing well. It was only last week that we spoke about continuous glucose monitoring. Have fun having a listen to that.

22:26Hit follow while you're there so that you never miss an installment of What's That Rush. Tell all your friends. Tell your friends. And have a great week. See you next time. See you then.