Oral rinses may prove a powerful tool for Coronavirus control.

Through nearly six months of public awareness of SARS-CoV-2 and the resultant COVID-19 outbreak, scientists and researchers have been learning—and changing recommendations.

Masks are effective in preventing the spread of COVID-19 (CDC); healthy people should wear masks only if caring for coronavirus patients (WHO).

Gloves help prevent infection; gloves increase risk of infection.

Mouthwash is ineffective to help prevent COVID-19; mouthwash may fight coronavirus.

The back and forth can be confusing, even for highly educated professionals. Yet, there is method in the madness, and sometimes, serendipitous discoveries emerge.

The Scientific Method, while ultimately effective, can be messy.

Revision of prevailing wisdom can happen when a “novel” virus appears that has not been exhaustively studied. The Scientific Method, while ultimately effective, can be messy—especially under urgent conditions—because it is an intrinsically “trial and error” process that develops theories more by eliminating what’s false than by establishing what’s true.


As the great Renaissance artist, Michelangelo Buonarroti, is credited with saying, “The sculpture is already complete within the marble block before I start my work. I just have to chisel away the superfluous material.”

Indeed, as dedicated scientists know, there is art even to science. The best theories begin with imagination. "Imagination is more important than knowledge,” said Albert Einstein. “For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution."

As scientists and researchers, we constantly carve away what is inconsistent, contradictory or not supported by empirical research.

“I saw the angel in the marble and carved until I set him free,” said Michelangelo.

The great 20th-Century Philosopher and Critical-Rationalist, Sir Karl Popper distinguished science from non-science through what he called “falsification.”

The growth of human knowledge proceeds from our problems and from our attempts to solve them.

As the Stanford Encyclopedia of Philosophy has it,

Karl Popper
Karl Popper

For Popper accordingly, the growth of human knowledge proceeds from our problems and from our attempts to solve them. These attempts involve the formulation of theories, which, if they are to explain anomalies [that] exist with respect to earlier theories, must go beyond existing knowledge and therefore require a leap of the imagination. For this reason, Popper places special emphasis on the role played by the independent creative imagination in the formulation of theory. The centrality and priority of problems in Popper’s account of science is paramount, and it is this which leads him to characterise scientists as ‘problem-solvers.’ In this deductive procedure, conclusions are inferred from a tentative hypothesis. These conclusions are then compared with one another and with other relevant statements to determine whether they falsify or corroborate the hypothesis.

We can only eliminate those theories [that] are demonstrably false, and rationally choose between the remaining, unfalsified theories.

The devil is in the details, but the angel may just be in the bigger picture. One person sees a humble oral rinse and concludes its contribution to controlling COVID-19 is negligible; another sees a complex and varied mixture of chemicals with the potential to be used as a weapon in the molecular-scale biochemical war inside the human body…and challenges existing theories by asking, “what if?”

Scientific theories, for [Popper], are not inductively inferred from experience, nor is scientific experimentation carried out with a view to verifying or finally establishing the truth of theories; rather, all knowledge is provisional, conjectural, hypothetical—we can never finally prove our scientific theories, we can merely (provisionally) confirm or (conclusively) refute them…For it is only by critical thought that we can eliminate false theories, and determine which of the remaining theories is the best available one, in the sense of possessing the highest level of explanatory force and predictive power.


dental response to covid


While a dichotomy of theories can exist, each propped up by select data, we choose the theory “possessing the highest level of explanatory force and predictive power.”

Such it is with the efficacy of commercial mouthwashes in the fight against Coronavirus; an evolution in thinking is taking place.

Dr. Valerie O'Donnell
Dr. Valerie O'Donnell

A brand new review of research and known mechanisms was published in the American Physiological Society’s Function on June 5, 2020: “Potential Role of Oral Rinses Targeting the Viral Lipid Envelope in SARS-CoV-2 Infection.” A multidisciplinary team of researchers at Cardiff University School of Medicine, led by Dr. Valerie O’Donnell, compiled a number of studies and concluded there is a “major clinical need” for additional research. O’Donnell is Director, Division of Infection and Immunity and Co-Director of Systems Immunity Research Institute at Cardiff.

“Emerging studies increasingly demonstrate the importance of the throat and salivary glands as sites of virus replication and transmission in early COVID-19 disease,” reads the study’s Abstract.

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A lipid envelope derived from host cellular membranes—sometimes at the plasma membrane, other times at the nuclear membrane, endoplasmic reticulum or Golgi complex—surrounds Coronavirus, as it does with other viruses including influenza and herpes simplex. As such, for many viruses, the lipid envelope is chemically the same as the host membrane from which it is derived, giving us important information on potential treatments.

While research has previously identified mechanisms of viral lipid membrane disruption by available dental mouthwash components—including ethanol, chlorhexidine, cetylpyridinium chloride, hydrogen peroxide, and povidone-iodine—“there has been no discussion about the potential role of oral rinsing in preventing [COVID-19] transmission,” according to O’Donnell…until now.

Mouthwashes may destroy the lipid envelope surrounding coronaviruses, thereby inhibiting virus replication in the mouth and throat.

“We highlight that already-published research on other enveloped viruses, including coronaviruses, directly supports the idea that oral rinsing should be considered as a potential way to reduce transmission of SARS-CoV-2,” according to the Cardiff review. “Research to test this could include evaluating existing or specifically tailored new formulations in well-designed viral inactivation assays, then in clinical trials.”


The implication is that widely available mouthwashes may destroy the lipid envelope surrounding coronaviruses, thereby inhibiting virus replication in the mouth and throat.

While current WHO and CDC recommendations focus on the use of personal protective equipment (PPE)—including facemasks, alcohol-based sanitizers, and surface sanitation—to reduce the spread of the virus, they have not yet addressed oral hygiene.

“It is becoming increasingly recognised that the throat is a major site of replication and shedding of virus in COVID-19 illness, and that viral load is important. Throat and sputum are abundant in particles, which peak 5-6 days after symptom onset, and decline thereafter.”

The potential for mouthwashes to “either dampen or reduce viral load, particularly for vulnerable individuals or healthcare workers,” may make mouthwash a significant player in the battle. “We don’t have any ways to do this currently,” according to O’Donnell.

“Assuming that the throat is a major site of replication in early stages (even before symptoms are apparent), then oral washing using agents that could damage or destroy the lipid envelope have the potential to reduce viral load in the oropharynx.”

Prior to COVID-19, the CDC had already recommended that dentists have patients use mouthwash before procedures for preventing respiratory diseases, which are “based on theoretical benefit, not benefit proven through clinical trials, which haven’t been conducted yet,” according to O’Donnell.

Interestingly, three industry-sponsored studies indicate “mouthwashes containing essential oils with 21-27% ethanol can inactivate enveloped viruses, both in the lab and in humans, with the likely mechanism being damage to the lipid envelope.”

Other potential benefits are also being explored. Meta-studies compiled by the Cardiff study reveal that “Chlorhexidine (rinse or gel) can reduce risk of ventilator-associated (bacterial) pneumonia in patients undergoing mechanical ventilation, although causative organisms were not described.” That could potentially play a role in improving survival rates.

Additional research is urgently needed, but in the meantime—knowing the already-established oral health benefits of mouthwashes—it makes sense for dentists to make its use a routine part of every treatment. It seems that humble mouthwash may be and an unexpected powerhouse in the fight against COVID-19.


Author: Kelly John Walker is Senior Writer and Editor with Strategic Dentistry, the parent company of DOCS Education. He holds a Master of Science (MS) degree in Environmental Science from New Mexico State University and a Bachelor of Arts (BA) in English Composition.


Works Cited

O’Donnell, et al. “Potential Role of Oral Rinses Targeting the Viral Lipid Envelope in SARS-CoV-2 Infection.” Function, Volume 1, Issue 1, 2020 June.

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