The science

What the research actually says about bad breath.

The published work we build on, with the reference and a direct link to each one. Every link opens the source. Read them yourself.

Where the smell comes from

Origin

It starts in your mouth, not your stomach

Memon MA and colleagues · Oral Diseases · 2023 · systematic review

This review pulled together the published work on what causes bad breath. It found that factors inside the mouth cause 80 to 90 percent of cases. A coated tongue is named as one of the leading ones.

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United States

How common it is here

StatPearls, hosted by the National Library of Medicine · chapter updated 2023 · and the American Dental Association

StatPearls is a free medical reference library that sits on the National Institutes of Health website. Its chapter on halitosis puts causes inside the mouth at nearly 80 to 85 percent of all cases, and reports that around 50 percent of people in the United States have dealt with it. The American Dental Association gives the same 50 percent figure on its public health pages.

Read it correctly. That 50 percent counts people over a whole lifetime, and it is what people report about themselves. It is not a count of how many Americans have bad breath today. No national survey measures that.

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Worldwide

Roughly one person in three

Silva MF and colleagues · Clinical Oral Investigations · 2018 · 13 population studies pooled

Pooling 13 studies, the authors put the combined prevalence at 31.8 percent, with a range of 24.6 to 39.0.

Read it correctly. The authors themselves report high variation between the studies they pooled. Some measured with an instrument, others simply asked people. Treat 31.8 percent as an order of magnitude, not a hard count. And none of the included studies is presented as United States data.

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Why the usual moves stop too early

The surface

The coating sits down in the grooves

Bernardi S, Marzo G, Continenza MA · Acta Stomatologica Croatica · 2016 · preliminary study, one subject

The authors took an impression of the tongue surface and measured how deep the grooves between the bumps run. Where coating was easy to see, they measured about 0.3 mm. Where little coating showed, about 0.21 mm. They conclude that the shape of the surface influences where the coating settles.

Read it correctly. This was a first look at a single person. Treat it as a starting point, not as proof.

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The clock

Scraping works, and then it stops

Seemann R, Kison A, Bizhang M, Zimmer S · Journal of the American Dental Association · 2001 · 30 subjects, crossover

Thirty people cleaned their tongue with three different tools on four separate mornings, a week apart. A tongue cleaner cut the smell producing gases by 42 percent, a scraper by 40 percent, a toothbrush by 33 percent. But the researchers could not detect a significant drop past 30 minutes in a single subject. They wrote that the value for controlling mouth odor stays questionable, because the effect is so short.

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The honest one

Nobody has shown a lasting fix yet

Kumbargere Nagraj S and colleagues · Cochrane Database of Systematic Reviews · 2019 · 44 trials, 1,809 people

This review gathered every trial it could find on treatments for bad breath. For mechanical tongue cleaning, and for mouthrinses, it rated the evidence very low certainty. Most trials followed people for only one to four weeks. Exactly one ran as far as three months.

We link this one because it cuts against us too. If anyone tells you the science is settled on any of this, they have not read it. This is where it actually stands.

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The paradox

Even dental students report it

Ashwath B, Vijayalakshmi R, Malini S · Journal of Indian Society of Periodontology · 2014 · 259 students

Researchers surveyed dental students, people who study mouths for a living. In the paper's results table, 21.7 percent of the men and 35.3 percent of the women said they had noticed their own bad breath. The authors write that tongue cleaning in this group was very minimal, and point to that as one likely reason.

Read it correctly. The summary at the top of this paper prints different figures than its own results table. We use the table figures, which are also the ones the National Library of Medicine quotes.

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What happens under the film

The shield

The film is built to keep antiseptics out

Jakubovics NS and colleagues · Periodontology 2000 · 2021 · review

Dental plaque is not loose bacteria. The cells sit inside a sticky matrix they build themselves, made of sugars, proteins, DNA and fats. In the authors' own words, that matrix protects the cells against chemical and physical insults and hinders the eradication of pathogenic dental plaque. That is the layer a rinse has to get through.

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The shield

Under a biofilm, bacteria hold out up to a thousand times better

Mah TFC, O’Toole GA · Trends in Microbiology · 2001 · review

This is the reference review on why biofilms are so hard to treat. Cells growing inside a biofilm are reported to be 10 to 1,000 times less susceptible to antimicrobial agents than the same cells floating free. The authors walk through the reasons: the agent does not diffuse through the matrix, the cells inside grow slowly, and the biofilm switches on its own defences.

Read it correctly. This is about antimicrobial agents and biofilms in general, across many species. It is not a measurement of what one mouthwash does to one tongue. It is here to show the size of the problem the film creates.

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The dose

Under the film, it takes far more of the same product

Lee SY, Lee SY · Biocontrol Science · 2019 · 80 streptococcus strains

Researchers tested the same bacteria two ways, free floating and grown into a biofilm. Free floating, CPC stopped them at 0.06 to 1.95 micrograms per milliliter. Grown into a biofilm, it took 3.91 to 31.25 to stop them and 7.81 to 62.50 to kill them. The authors report the biofilm figures ran under 30 times higher for most species, and more than 200 times higher for some. Same bacteria, same product. The film is the whole difference.

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The active

With no film over them, CPC works fast in a dish

Schaeffer LM and colleagues · The Journal of Clinical Dentistry · 2011 · laboratory test

This was a dish, not a mouth. The bacteria were free floating with no biofilm over them. A rinse holding 0.075 percent CPC cut them by more than 99.9 percent in 30 seconds.

Read it correctly, because this number gets abused. It is a laboratory result, on bare bacteria, at that one concentration, in a dish. It is not what happens on a coated tongue, and it is not a number we claim for our product. It is here for one reason: to show what changes once the film is off. The work was done by researchers at a large oral care manufacturer.

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The active

A CPC rinse also lowers bacteria inside a biofilm

Latimer J and colleagues · BMC Microbiology · 2015 · volume 15, article 169

Researchers tested rinses holding 0.075 percent CPC against free floating mouth bacteria and against biofilms grown from real saliva. The rinses cut viable bacteria by more than 3 logs in the free floating tests, and lowered viability inside the biofilms too.

Note the source. This study was funded by a company that sells mouthwash, and one of its authors works there.

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What the jet does

Safety

A pulsed jet does not hurt the tissue

Cobb CM, Rodgers RL, Killoy WJ · Journal of Periodontology · 1988 · 32 samples

Researchers ran a pulsed water jet with saline into untreated gum pockets, then looked at the tissue under an electron microscope. They compared 16 treated samples against 16 untreated ones, at depths from 0 to 6 mm. The treated samples held far fewer bacteria at the shallower levels. The tissue itself showed no difference, and the authors concluded that pulsed irrigation is not injurious to the soft tissues.

Read it correctly. This was gum pockets, not the tongue. And at the deepest level, 5 to 6 mm, a mixed population was still there.

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Twelve weeks

Daily water flossing, measured over three months

Xu X and colleagues · Clinical Oral Investigations · 2023 · 70 enrolled, 63 finished

People were split into two groups for 12 weeks. One added a daily water flosser to brushing, the other only brushed. By week 12 the water flosser group had less mouth odor than at their own starting point. Their bacteria had also shifted toward an oxygen tolerant mix, with less Prevotella.

Read it correctly. This trial was on teeth and gums. It did not test the tongue, and it did not test our product.

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Why mornings are worse

Saliva

Less saliva, heavier coating, worse morning breath

Popa M and colleagues · Journal of Clinical Medicine · 2025 · 92 people

Researchers measured resting saliva flow, scored the coating on the tongue, and measured the smell producing gases. People who reported morning bad breath made less saliva at rest, 0.2 against 0.3 milliliters a minute. Their tongue coating scored higher. Their gas readings averaged 272.9 parts per billion against 163.7 in the others.

Read it correctly. This is a snapshot of one group at one moment. It shows things that travel together. It does not show which one causes which.

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These studies are about bad breath, the bacteria on the tongue, and biofilm in general. None of them tested this product. They explain the reasoning it is built on. Results vary from one person to the next. Bad breath can also come from outside the mouth. If yours does, nothing on this page applies to you, and you should see a dentist or a doctor.

Want to go after the source?

See the water flosser →