A surprising, inexpensive tool is available to us. Why aren’t more people studying the value of mouthwashes and nasal rinses?
The obvious answer, of course, is that it’s not profitable. Salt water costs pennies; other products with antiviral activity cost just a few dollars. Why study these common antiseptics when you can have exotic new drugs and lucrative vaccines.
Gilead’s Remdesivir, for example, costs more than $3100 per treatment, although it was developed with $99 million of taxpayer funding. Similarly, vaccines in development have expected price tags ranging from $4 for AstraZeneca-Oxford’s candidate, $13 for India’s Serum Institute’s, $32-37 for Moderna’s taxpayer funded vaccine, to $145 for that from SinoPharm.
But there are tantalizing clues that simple measures reduce viral load and might help prevent transmission of SARS-CoV-2, the virus that causes Covid-19. These need to be studied urgently.
The most thorough report, an extensive review of research on mouthwashes, comes from University Hospital of Wales in Cardiff. Professors Valerie O’Donnell and David Thomas explain that the SARS-CoV-2 virus (and other respiratory viruses) are surrounded by a fatty membrane. This can be disrupted by soap or detergents, which is why hand washing is so important. There are many common chemicals which also have this effect. We already use 70% ethanol (usually in hand sanitizers). In an abstract from the International Association of Dental Research meeting in 2010, industry-sponsored researchers showed that a 30 second exposure to 21.6% ethanol with essential oils (Cool Mint Listerine, which contains eucalyptol, menthol, thymol and methyl salicylate) led to >99.99% reduction in a strain of H1N1 Influenza A in tissue culture.
Chlorhexidine (Hibiclens and other) has long been used to clean skin before surgery. It’s also been used by cancer patients to help with oral health and reduce the likelihood of infection from gum infections. Chlorhexidine has broad antibacterial activity but does not have good antiviral activity and should not be used for coronavirus.
Iodine also has been used to clean skin wounds for decades. It has been used as a gargle in Japan and India for sore throats because of it’s antiviral activity.
Contact with hydrogen peroxide, at a concentration of 0.5%, will inactivate various viruses with fatty envelopes like coronavirus.
Cetylpyridinium chloride (CPC), another type of antiseptic, has antiviral effects as well. It’s been used in mouthwashes and throat lozenges.
One small randomized controlled study of nasal irrigation and gargling with saltwater showed a shorter illness, 35% reduction in infecting other members of the household and reduction in viral shedding.
Finally, even gargling with chlorinated tap water reduced respiratory infections in a study in Japan.
Another small study from Malaysia showed better reduction of virus with iodine or essential oils compared to water or no treatment.
A recent study from Germany found Listerine, Iso-Betadine and Dequonal mouthwashes to be most effective against three strains of SARS-CoV-2 of eight commercially available products.
There are many questions about this approach. Can the viral load be reduced enough through gargling and/or nasal washes (e.g., Neti pot) to be a worthwhile preventative? Which product is most effective? Would some combination be better? How much contact time is needed? Would putting these compounds in a chewing gum or lozenge to prolong contact be more effective? What effects do these antiseptics have on the oral flora (microbiome). Do we need nasal washes, mouth washes, or both?
What side effects might appear? (We already know of tooth staining and rare allergic reactions).
There is one report on the CURE ID Drug Repurposing database of an unpublished case where excessive use of iodine mouthwash and nasal spray resulted in increased iodine levels and mild bleeding. The problem resolved by stopping aspirin and reducing the iodine use. This is one example of the value of CURE ID and the need to have more health care workers submit cases, which is easily done. (The database and discussion forum is a project of the FDA and NIH’s NCATS. It is currently only accessible to health care workers).
Dr. O’Donnell stresses the need for urgent clinical trials for effectiveness against SARS-CoV-2: “Safe use of mouthwash – as in gargling – has so far not been considered by public health bodies in the UK” or elsewhere, it would seem. She stressed that “There is quite a bit of interest now…[there are] several studies assessing oral targeting of virus now around the world.
Given the magnitude of the Covid-19 pandemic, it would seem reasonable to suggest people begin one of these mouthwashes or gargles and nasal irrigation at the onset of respiratory symptoms, as a way to perhaps reduce their infectivity. Don’t forget to mask up, as well.