Do You Really Need Mouthwash?

Mouthwash feels good. Killing 99.9% of all germs. Obliterating dreaded plaque. Annihilating gingivitis. Mmm, minty fresh breath! So I’m not sure exactly how to break the news.

I guess I’ll just spit it out.

For people with good oral health who brush and floss regularly, there’s not much scientific evidence that mouthwash offers additional benefit. And when scientists really sink their teeth into analyzing the available research, they find some mouthwashes can do more harm than good.

To be clear, specific types of mouthwash can benefit people with certain oral health problems — a dentist can help you determine your potential need. But to get beyond the sparkling claims that fuel more than $6 billion in annual global sales, I’ve brushed up on the latest scientific literature and reached out to multiple experts to figure out who might benefit from mouthwash, who likely doesn’t need it, and how we can all decide.

The result is a mouthful of conflicting claims and suggestions. So here’s the single most solid and important takeaway experts agree on:

“Mouthwash is in no way a substitute for the mechanical removal of plaque and bacteria from the mouth that is accomplished by thorough brushing and flossing,” says Schelli Stedke, MDH, a dental hygienist and patient care lead at Dentistry.One. “If mouthwash is used, it should only be used as an adjunct to brushing and flossing to achieve optimal oral hygiene.”

Open wide

Your mouth is a gateway to your overall physical and mental health, with around 700 types of bacteria serving as the front lines for everything that happens after you eat or drink. Poor oral hygiene leads to more than loose, rotting teeth. It also raises the risk of numerous illnesses, including heart disease, cancer and even dementia. Here are the primary oral health problems to be concerned about:

• Plaque: Sticky bacteria-laden film covers teeth, eating away tooth enamel and causing cavities.
• Gingivitis: Reversible infection in the gums, also caused by plaque, causing swollen, bleeding gums and bad breath.
• Periodontitis: Advanced gingivitis, also called gum disease, this chronic infection makes teeth loose and prone to falling out.
• Dry mouth: Inadequate flow of saliva, caused by some medications or underlying conditions, which hampers the mouth’s natural bacteria-fighting ability.

Any of the above conditions can lead to bad breath, or halitosis, as it’s called, which is caused by volatile sulfur compounds indicating oral decay, or generated by such things as smoking, coffee or garlic.

Over-the-counter mouthwashes promising better oral health are called therapeutic products, as opposed to cosmetic varieties that pledge to control bad breath or whiten your teeth. (This article does not discuss whiteners.) It’s important to understand the intent of whatever formulation you choose. Even then, however, it’s entirely unclear how much benefit you might expect.

What the research says

A comprehensive review of studies on the effects of mouthwashes, published recently in the International Dental Journal, concludes there’s not enough evidence to make any substantiated recommendations for general mouthwash use. The researchers did determine this, however: “Mouthwashes may not be of much value in those with good periodontal health.”

Meanwhile, an emerging but still inconclusive body of research indicates potential harm, in part because common over-the-counter mouthwashes kill bad and good bacteria indiscriminately. This risk has been documented among people who use mouthwash regularly (twice daily) and so may not apply so much to occasional use.

“If mouthwash is overused, there is concern that not only are the unhealthy bacteria killed, but so are the healthy bacteria which can lead to imbalances in our oral flora as the bacteria repopulate,” Stedke explains in an email.

Mark Burhenne, DDS, who opines on Ask the Dentist, has a decidedly dim view of the current state of understanding. He says mouthwash is akin to putting “unnecessary antibiotics in your mouth,” disrupting the healthy production of saliva and destroying your oral microbiome, which ironically raises the risk of all the conditions mouthwash aims to wash away.

“Not only will mouthwash not live up to the claims spouted in expensive commercials and on flashy labels, but conventional mouthwash can actually make your dental and oral health problems worse,” Burhenne writes.

Another concern rarely mentioned: Active and supposedly inactive ingredients vary significantly from brand to brand, so you not only need to know what problem you’re trying to solve, but you should consider which set of ingredients would best do the job.

“Depending on your oral health needs, mouthwash can be a helpful addition to your daily routine,” says Ruchi Sahota, DDS, a practicing dentist in California who advises consumers as a spokesperson for the American Dental Association. “However, we are all different, so a conversation with your dentist can help you decide whether you need a mouthwash and what kind of mouthwash to use.”

Children under six should not use mouthwash without specific advice from a dentist. “They may accidentally swallow large amounts of the mouthwash, which can cause nausea, vomiting and intoxication, due to the alcohol content in some rinses,” Sahota says.

What’s in your mouthwash?

Here’s just a handful of the most common mouthwash ingredients that can have notable effects:

Alcohol: Perhaps the most common ingredient found in many over-the-counter mouthwashes is alcohol. It can cause the mouth to dry out — a feeling you might not enjoy. It’s thought to kill both bad and good bacteria. Importantly, a 2019 review of eight studies found tentative evidence linking alcohol-based mouthwashes to a higher risk for oral cancer. More research is needed to determine if the connection is real.

Essential oils: Menthol and eucalyptol are among the common “natural” ingredients found in many mouthwashes. Natural ingredients can mean anything from tea leaves to cyanide, but fortunately there is some research suggesting these two ingredients are more effective than a placebo at reducing plaque and gingivitis. There are hints they help with bad breath, but generally only as a coverup, not a solution. Beyond those two ingredients, there are oodles of essential oils used in a variety of mouthwashes and accompanied by numerous flowery claims and a dearth of evidence to suggest how well they might work.

Chlorhexidine: Available only by prescription in the US, chlorhexidine is generally perceived as effective (when used in addition to brushing and flossing) in helping battle diagnosed periodontal diseases. It may be prescribed by a dentist for a patient who has gingivitis or periodontitis, says Andre Paes, DDS, an associate professor of periodontics at Case Western Reserve University’s School of Dental Medicine. But it isn’t without side effects, which include stained teeth and an altered sense of taste. One study found chlorhexidine can negatively alter the natural acidity in the mouth, potentially leading to — again, the irony — tooth damage. It is typically prescribed for short-duration use to help battle a diagnosed oral disease.

“Both chlorhexidine and essential oils can be used to help control plaque and gingivitis,” Sahota tells me.

The short list above barely scratches the surface of common ingredients. Here’s what’s in one of the best-selling brands, Listerine Ultraclean:

• Active ingredients: eucalyptol, menthol, methyl salicylate, and thymol.
• Inactive ingredients: water, alcohol (21.6% by volume), sorbitol, poloxamer 407, benzoic acid, and a half-dozen other hard-to-pronounce things.

I find it interesting that alcohol is considered “inactive,” when evidence suggests entirely otherwise. There’s very little definitive research to help us sort through the benefits and risks of each of these ingredients, or others you might find in your favorite brand. So let’s pull back for a broader view.

General risks of mouthwashes

Among the most alarming studies in this field is a 2021 analysis that found frequent users of mouthwash (twice or more daily) had a “significant higher risk of hypertension,” meaning high blood pressure, than less-frequent users, and more than double the risk of non-users. The findings don’t prove cause and effect, but potentially confounding factors like drinking, smoking and physical fitness were factored into the results. The types of mouthwashes were not singled out, but most people said they used theirs to clean their mouths or freshen breath, which suggests a cross-section of popular products.

A 2017 study by the same researchers linked frequent use to a greater risk of type 2 diabetes.

Then in 2018, a separate research team, reporting in the British Dental Journal, linked frequent mouthwash use to a 50% higher combined risk of developing prediabetes or diabetes. The scientists think the antibacterial effects of common mouthwashes reduce nitric oxide in the body, which in turn has been linked to insulin resistance as well as high blood pressure.

However, these studies on the whole remain inconclusive, Stedke says, due to shortcomings that include small numbers of participants in some cases, or self-reporting instead of randomized controlled trials. Some involved overweight and obese individuals at increased risk for developing diabetes and/or hypertension. While the body of work is interesting, she says, more research is needed.

Another risk of mouthwashes seems to easily pass the smell test: If used after brushing — which is how I’ve always used it — mouthwash dilutes fluoride from toothpaste, defeating some of its cavity-fighting effects.

You should therefore wait 20 to 30 minutes after brushing to use mouthwash, Paes says in an email. (Such an instruction ought to be on labels, but often is not.)

Or you can use a mouthwash that contains fluoride. However, while experts agree fluoride helps fight plaque and tooth decay, there’s insufficient evidence to suggest back-to-back doses (brushing then rinsing) will make a difference. “There is limited available specific evidence on the effectiveness of fluoride mouthwashes on dental plaque levels and likewise a lack of evidence on its effectiveness relating to gingivitis/periodontal diseases,” researchers concluded in the International Dental Journal review.

If bad breath is your big worry, pick a mouthwash that aims to reduce those bacteria-generated volatile sulfur compounds (VSCs). “Some mouthwashes simply cover odor with a fresh scent such as mint, with no therapeutic benefit,” Stedke says. “Others may choose antimicrobial mouthwashes that help reduce the number of VSCs in the mouth by killing bacteria. Ingredients that do this include chlorine dioxide, cetyl pyridinium chloride, and essential oils.”

Note that any number of mouthwash ingredients can be simply irritating, which may or may not be a sign of long-term negative health effects, but suggest that some common sense is in order.

“It is not abnormal for mouthwash to cause a tingly, or even a burning sensation when used, especially since part of the reason we use it is to freshen our mouths,” Stedke says. “However, ongoing signs of irritation from mouthwash like extended burning in the mouth, or on the tongue or lips, ulcers inside the mouth, or sloughing of tissue from the cheeks may be an indication to switch to a milder formula or stop altogether for some time.”

What about oil pulling and… seaweed?

Oil pulling, an alternative medicine technique from India, has surged in popularity in Western countries over the past year or two, with Google searches skyrocketing. It involves swishing coconut oil or some other sort of edible oil around for 10 to 20 minutes, with the promise of removing bacteria and reducing plaque, among several other claims.

You can find several seemingly credible articles on prominent health sites that repeat positive claims about oil pulling. They are all long on maybes and short on evidence.

Two small preliminary studies of oil pulling found positive effects on oral health — and those are the studies you will find oft-cited. Subsequent randomized control trials revealed no benefit, according to the recent review in the International Dental Journal.

Testimonials and anecdotes abound, which are great for anyone who wants to profit from the trend, but are less than distasteful in terms of scientific validity.

“There is no evidence that oil pulling can prevent cavities, detoxify the body, strengthen teeth, treat cancer or reduce headaches, despite such claims made online,” Anthony King, a journalist who reviewed the existing research, writes in a separate analysis in the British Dental Journal. “Many of these reputed benefits reek of pseudoscience quackery of the worst kind, promising exceptional health benefits without scientific evidence to support them.”

Numerous other mouthwash ingredients await further study to indicate their effectiveness (or lack of it) for routine oral hygiene. Among them: saltwater, baking soda, propolis, charcoal and seaweed.

What really works

Brushing aside the results of a few small and inconclusive studies, a helpful consensus has emerged to serve the majority of people: Tend to your oral health by eating well, brushing with fluoride toothpaste twice a day, flossing daily, and brushing your tongue, too.

The National Institute of Dental and Craniofacial Research offers in-depth oral hygiene tips, including details on proper brushing and flossing techniques and, interestingly, no mention of mouthwash except the possibility of dentists recommending a fluoride rinse for people at high risk of tooth decay.

If you think you need mouthwash, many experts advise consulting your dentist first, and looking for the ADA Seal of Acceptance that earmarks products considered safe and effective.

And don’t buy into the marketing hype.

“If it sounds too good to be true, it probably is,” Stedke says. “If a product claims to whiten teeth, cure bad breath, prevent gum disease, and promise you will never have a cavity again, you may want to steer clear.”