Does Povidone Iodine (ie, Betadine), Listerine, Alcohol 70% Gargles Work Against COVID-19? Video on Dr. Cremers use of diluted povidone iodine (ie Betadine) to decrease viral loads.

Since the original post below, more and more papers are coming out on the use of Povidone Iodine (ie, Betadine), Listerine Cool Mint (see paper below: Virucidal efficacy of different oral rinses against SARSCoV2. The Journal of Infectious Diseases, 2020, see below **++**), Alcohol 70% mouth gargles to prevent COVID 19 or at least decrease the viral load if exposed to COVID-19. 

I just bought the below for my family as Listerine Cool Mint is not as disgusting as Povidone Iodine… The ability of Listerine to kill COVID-19 is interesting as it only has 20% alcohol and most studies I could find note 70% alcohol is best. I will personally likely put a couple of drops of Povidone Iodine in a little cup of Listerine until mores studies on humans are performed to prevent COVID-19. 

Original Post:

I think you can decrease the negative consequences of COVID if you catch it early AND are not allergic to Povidone Iodine/Betadine: so please check with you MD and always be around other people if you try Povidone Iodine for the first time and check your reaction on your skin first before trying below, in case you have a severe allergic reaction. 

Povidone iodine is not an alternative to the use of PPEs, like masks, protective goggles, washing hands well after using 70% alcohol (which is my preferred way to wash my hands though washing hands alone for at least 20 seconds has been shown to work to kill COVID as well), social distancing, shields, etc. 

Also note that people who are allergic to shellfish have a 3% chance of being allergic to iodine which is about the same as patients with no known shellfish allergy. But check with your MD before trying below. 

I had posted about this in the past: I am convinced that gargling Povidone Iodine (5%) (ie, Betadine diluted to 5%) and/or sticking cue tips soaked in Povidone Iodine or Betadine (and/or mixed with 70% alcohol) up your nose decreases viral loads of any virus and can prevent a full infection. I have also thought that trying to aerosolize Povidone Iodine (5%) may kill deeper infections in patients with COVID-19 pneumonia but this study has not been done yet. 

As with all information on this blog, please check with your PCP/doctor before trying anything new. 

Finally, there is a good letter to the editor below that outlines how to use it.

How to Use Povidone Iodine for COVID-19 prevention:

A. Published Way of How to Mix and Use Povidone-Iodine (PVP-I) 
  • 1.
    Apply nasal and oral PVP-I every 2–3 h, up to 4×/day 
    • a.
      Have suspected/confirmed SARS-CoV-2 infection
    • b.
      Are undergoing high-risk procedures (e.g. those involving nasal mucosal, oral, pharyngeal, and pulmonary secretions)
    • c.
      Are from COVID-19 hotspots

  • 2.
    Apply nasal and oral PVP-I prior to and after patient contact (with repeated contact, apply every 2–3 h, up to 4×/day) 
    • a.
      Are involved in care of patients with suspected/confirmed SARS-CoV-2 infection
    • b.
      Are involved in high-risk procedures of patients in COVID-19 hotspots
    • c.
      Lack adequate PPE (e.g. N95, PAPR)
  • 3.
    Optional nasal and oral application of PVP-I every 2–3 h, up to 4×/day 
    • a.
      High-risk procedures in asymptomatic patients
    • b.
      COVID-19 hotspots

**B. Dr. Cremers’s Way to Use 

I have not published this data yet. But I have used 5% dilution of Povidone Iodine for years as a gargle and cuetips up nose to decrease viral loads for influenza and the common cold. 
a. I take 1ml of Povidone Iodine
b. I then mix it with 1ml of tap water: suck it up in syringe or just gargle it as long as I can. Below studies indicate 30 seconds is likely enough although second says 60seconds: **++
c.  I do the same to soak cuetips and then & then irrigate my nose (each nostril) 
d. I repeat this usually 4x per day or as often as I feel my throat starting to hurt again. 
e. You may need to mix a few more drops of Povidone Iodine with an equivalent amount of drops for a greater amount. Some studies have published that even more diluted PI works to kill viruses. 5% may be overkill. PI may make you or your child vomit. I do not mind it but my kids hate it. I have used 70% Ethylene Alcohol also for these gargles & nasal swabs which is a bit more tolerated. 

Sometimes you need more. Often I will feel my nose or throat feeling “funny” before a virus attacks. 

With COVID, friends and colleagues have noted they do NOT have any weird feelings in their throat or nose until the headache and fever hits them hard. Still, if I got a headache & fever, I would still gargle Povidone Iodine (5%) and put it in my nose & massage my neck muscles & do the usual things I do to prevent the full attack and entry of the virus into my bloodstream (which is what elicits a fever). 

Thus, I would still gargle 

A word of caution: What are the risks of Povidone Iodine:
1. Do not use if you are allergic to Iodine. If you are allergic to shellfish, there is about a 3% chance to will be allergic to iodine, so please check with your MD first before using povidone iodine/ Betadine. 
2. PI tastes terrible & can make one vomit, so use with caution initially and maybe dilute it more at the beginning to 23% & hold in longer for 15 seconds. 
3. If one were to use this extensively, there is a rare report of raising one’s blood iodine level which could be a risky but this is rare. 

I still recommend the following:
1. Getting some sun exposure to naturally increase Vitamin D levels without getting a sun burn. 
2. Eat a low inflammatory diet: low/no gluten; low/no sugar
3. Consider intermittent fasting: don’t eat until after noon. Stop eating before 6-7pm. 
4. Exercise: get your 10,000 steps in at least per day.
5. Pray/meditate: get good sleep
6. Eat green leafy vegetables every day: get your natural anti-oxidants daily

7. Suck on Cold Eeze or zinc if you start to get sick

Zinc Lozenges: we have 6mo supply on this. If you start to feel yourself getting sick, start taking Zinc (my favorite is Sugar Free Coldeeze). 

8. A good hot shower & a good neck massage can do wonders to prevent the headache that can happen with viruses; likely acupuncture works for this as well –though I would avoid acupuncture during the COVID epidemic for now. 

I hope this helps.



Consideration of povidone-iodine as a public health intervention for COVID-19: Utilization as “Personal Protective Equipment” for frontline providers exposed in high-risk head and neck and skull base oncology care

Leila J. Mady, Mark W. Kubik, […], and Nicholas R. Rowan

Letter to the Editor
In response to the novel coronavirus SARS-CoV-2, healthcare systems have been challenged to allocate scarce resources while striving to achieve distribution justice to meet the critical needs of the communities they serve. Though there are ongoing randomized trials evaluating the utility of systemic therapies, post-convalescent serum, and vaccine development, these interventions are costly and time intensive. Alternative therapies and preventative measures are needed now, not only to accelerate the flattening of the epidemiologic curve, but also safeguard providers and patients as we re-evaluate tiered surgical responses and operational processes moving forward.
Early investigations in China have suggested that cancer patients harbored a higher risk of infection compared with the overall population and that infected cancer patients, particularly those who received chemotherapy or underwent surgery within a month of infection, were more susceptible to the need for critical care, respiratory support, and mortality 
As viral load appears highest in the nasopharynx, and high in human saliva, these anatomical areas likely seed the lower airway and serve as one of the main reservoirs for aerosolized transmission and progression of pulmonary disease. Furthermore, viral loads of asymptomatic and symptomatic patients are similar, suggesting the transmission potential of asymptomatic/minimally symptomatic patients 
The utility and excellent safety profile of both topical nasal and oral solutions of PVP-I has long been recognized, especially at dilute concentrations (e.g. 0.001%). A detailed review of its virucidal activity against a wide range of common viruses, including SARS-CoV and MERS-CoV coronaviruses, is beyond the scope of this article 
Here we present a novel intervention strategy utilizing topical applications of PVP-I to attenuate nosocomial transmission of COVID-19 surrounding head and neck and skull base oncology care.
  • 1.
    Apply nasal and oral PVP-I every 2–3 h, up to 4×/day 
    • a.
      Have suspected/confirmed SARS-CoV-2 infection
    • b.
      Are undergoing high-risk procedures (e.g. those involving nasal mucosal, oral, pharyngeal, and pulmonary secretions)
    • c.
      Are from COVID-19 hotspots
  • 2.
    Apply nasal and oral PVP-I prior to and after patient contact (with repeated contact, apply every 2–3 h, up to 4×/day) 
    • a.
      Are involved in care of patients with suspected/confirmed SARS-CoV-2 infection
    • b.
      Are involved in high-risk procedures of patients in COVID-19 hotspots
    • c.
      Lack adequate PPE (e.g. N95, PAPR)
  • 3.
    Optional nasal and oral application of PVP-I every 2–3 h, up to 4×/day 
    • a.
      High-risk procedures in asymptomatic patients
    • b.
      COVID-19 hotspots
This strategy benefits from broad availability of materials, excellent safety profile and associated low costs. Given the ease of acquirement of materials, healthcare providers may immediately implement this intervention as a form of “personal protective equipment” to augment current practice recommendations. It is important to acknowledge that there is a potential risk in that prophylactic treatment of healthcare providers could increase susceptibility to SARS-CoV-2 infection by affecting mucociliary function or local immunity. As previously mentioned, and worth restating, we recommend a lower concentration out of an abundance of caution to minimize this untested possibility. Though we describe this protocol in the context of frontline providers caring for head and neck and skull base patients, this strategy may be applied to additional practitioners with occupational exposures. Let us flatten the epidemiologic curve 

Declaration of Competing Interest

The authors declared that there is no conflict of interest.

Article information

Oral Oncol
Published online 2020 Apr 16. 
Nicholas R. Rowan: 
Received 2020 Apr 12; Accepted 2020 Apr 15.
Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company’s public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre – including this research content – immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.




This (below after update) is from a ICU colleague in Seattle. I found this very helpful.

I would add: intermittent fasting and low carb diet helps immune system. As do many suggestions on this previous blog post (like eat more tumeric, curry, Vitamin D, etc): 

Personally, I have a low threshold –if feel any tingling in nose or sore throat coming on– for gargling & spitting out betadine/povidone iodine 5% (never bleach!) & sticking a cuetip (or rolled up tissue) into nostrils soaked a bit in 5%

Finally there is a clinical trial on using Povidone Iodine/Betadine to prevent COVID’s viral load and infection. Why is not every university doing this study??

COVID-19: Povidone-Iodine Intranasal Prophylaxis in Front-line Healthcare Personnel and Inpatients (PIIPPI)

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Identifier: NCT04364802
Recruitment Status 

First Posted 
Last Update Posted 
Information provided by (Responsible Party):
Alexandra Kejner, University of Kentucky

Go to  
Brief Summary:
Povidone-iodine (PVP-I) is a broad-spectrum antiseptic with activity against bacteria, fungi, and viruses. It has been previously used in both intranasal preparations against Methicillin Resistant Staphylococcus Aureus (MRSA) as well as oral preparations in in-vitro studies of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV), Middle Eastern Respiratory Syndrome Coronavirus (MERS-CoV), influenza H1N1, and rotavirus with good efficacy. This study will evaluate the efficacy of PVP-I as prophylaxis in Coronavirus Disease 2019 (COVID19)-negative front-line health care workers and hospital patients.

Condition or disease  Intervention/treatment  Phase 
COVID-19SARS-CoV 2 Drug: Povidone-Iodine Nasal Spray and Gargle Phase 2

The COVID-19 pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus – 2 (SARS-CoV-2), has been implicated in over 900,000 cases in the United States alone and has been found to affect as many as 28% of healthcare workers (HCW) worldwide. The most current statistics from Iceland, China, and Italy indicate that up to 50% of infected patients may be asymptomatic or with negligible symptomatology. This, added to the national shortage of personal protective equipment (PPE) and the need to reuse PPE, lends to the significantly increased risk to healthcare providers.
The highest concentration of viral particles resides within the nasopharynx. The virus is thought to spread via respiratory droplets with the potential for transmission via inhalation of droplets, contact to the nose and mouth with infected materials, and airborne transmission. Given that frontline workers are involved in high-risk procedures including intubation, bronchoscopy, proning patients (which can lead to droplet production) and in some cases are reusing PPE, finding ways to reduce viral load or viral exposure are paramount.
Povidone-iodine (PVP-I) is a broad-spectrum antiseptic with activity against bacteria, fungi, and viruses. It has been previously used in both intranasal preparations against MRSA as well as oral preparations in in-vitro studies of SARS-CoV, MERS-CoV, H1N1, and rotavirus with good efficacy.
Due to the known breadth of its antiviral activity and similarities in molecular structure, it can be extrapolated that PVP-I should have robust activity against SARS-CoV-2. Eggers et al found that at a concentration of 1% there was a reduction of viral activity of 99.99% in in-vitro assays. At 2 minutes, a concentration of 0.23% was enough to reduce viral loads appreciably.
PVP-I is widely used as an antiseptic and is well-tolerated and has been shown to have little to no effect on mucociliary clearance, olfaction, or thyroid function if iodine holidays are taken.
In this study, front line healthcare workers will be asked to complete a pre-participation survey and screened for COVID positivity. They will then be given premade PVP-I gargles and nasal sprays, as well as a calendar card to mark compliance. PVP-I nasal spray and gargle (10% diluted 1:30) will be used prior to the start of a shift, during “lunch break”, and at the end of shift. First, the nasal spray will be sprayed in the nose (2 sprays each naris). For adequate coverage, the participant should be able to taste the iodine or see it in the back of the throat. This should be left in place for 30 seconds. Then, the participant will gargle the solution for 30 seconds and not have anything to eat or drink by mouth for 30 minutes. Treatment will continue for 3 weeks, or until the healthcare worker presents with COVID symptoms. Participants will then be tested for COVID positivity and asked to fill out a second questionnaire assessing study tolerability. At completion of the study, they will be asked to turn in their calendar card to assess how many applications they were able to complete.
Given the high rate of asymptomatic carriers, a second arm will also be planned for patients who have a 7+ day hospitalization or who are set to undergo a significant surgical procedure. These patients will be offered participation in the study as well and will be given the same questionnaire and undergo preoperative testing if they consent. For patients in the study group, PVIP gargle and nasal sprays will be applied preoperatively or shortly after admission and enrollment in the study for the non-operative group. The patients will then be retested in 2 weeks or as directed by the presentation of symptoms concerning for infection with SARS-CoV-2.
Go to  
Study Type  Interventional  (Clinical Trial)
Estimated  250 participants
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)
Primary Purpose: Prevention
Official Title: Povidone-Iodine Intranasal for Prophylaxis in Front-line Health-care Personnel and Inpatients During the Sars-CoV-2 Pandemic
Actual  April 29, 2020
Estimated  May 2021
Estimated  May 2021
Resource links provided by the National Library of Medicine

Go to  
Arm  Intervention/treatment 
No Intervention: Healthcare Workers – Control

Front-line healthcare workers (FLCHW) who are negative for COVID will receive standard PPE and a pre- and post-study test for COVID-19.
Experimental: Healthcare Workers – PVP-I

Front-line healthcare workers (FLCHW) who are negative for COVID-19 will receive standard PPE and a pre- and post-study test for COVID-19. Additionally, they will receive PVP-I spray and gargle.
Drug: Povidone-Iodine Nasal Spray and Gargle

Healthcare workers will receive standard PPE and a pre- and post-study nasal swab COVID19 test. Additionally, they will receive povidone-iodine nasal spray and gargle (10% diluted 1:30) to use at the beginning of their shift, in the middle, and at the end of their shift.
No Intervention: Inpatients – Control

Inpatients who have a 7+ day hospitalization or who are set to undergo a significant surgical procedure will receive standard care and a pre- and post-study COVID-19 test.
Experimental: Inpatients – PVP-I

Inpatients who have a 7+ day hospitalization or who are set to undergo a significant surgical procedure will receive standard care and a pre- and post-study COVID-19 test. Additionally, they will receive PVP-I gargle and nasal sprays that will be applied shortly after admission or perioperatively.
Drug: Povidone-Iodine Nasal Spray and Gargle

Patients will receive standard of care treatment and a pre- and post-study nasal spray COVID19 test. Additionally, they will receive povidone-iodine nasal spray and gargle shortly after admission or preoperatively.

Go to  

Primary Outcome Measures 

  1. Percent of healthcare workers testing positive for COVID-19. [ Time Frame: 3 weeks ]
    Percent of healthcare workers that become positive for COVID-19 during the study.
  2. Percent of patients testing positive for COVID-9. [ Time Frame: 2 weeks ]
    Percent of patients that become positive for COVID-19 during the study.

Secondary Outcome Measures 

  1. PVP-I Ease of Use [ Time Frame: 3 weeks ]
    Patients will rate the ease of use for PVP-I treatment on a scale from 1-5 after the initial use. Lower scores indicate increased ease of use (1=”easy”) while higher scores indicate increased difficulty (5=”impossible”).
  2. PVP-I Comfort [ Time Frame: 3 weeks ]
    Patients will rate the comfort of PVP-I treatment on a scale from 1-5 after the initial use. Lower scores indicate increased comfort (1=”not so bad”) while higher scores indicate discomfort (5=”worst pain of my life”).

Other Outcome Measures:

  1. Adherence to treatment protocol [ Time Frame: 3 weeks ]
    Participants will fill out a daily questionnaire assessing treatment frequency. Adherence will be calculated as the percent of correct dosing.
Go to  

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, 

Ages Eligible for Study:   18 Years to 99 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Inclusion Criteria:
  • healthcare worker OR
  • patient with expected hospital stay of 7+ days OR
  • patient admitted for major surgery
  • COVID19 negative by nasal swab test
  • asymptomatic for COVID19
  • able to consent
Exclusion Criteria:
  • positive for COVID19 by nasal swab
  • symptomatic for COVID19
  • unable to consent


Povidone iodine

Sir, dentists and their assistants as front-line healthcare workers (HCW) in close contact with the upper aerodigestive tract are at especial risk of transmission of the coronavirus from patients. In early infection, viral titres of greater than 10
We have been examining the potential role of povidone iodine (PVP-I) in the reduction of the risk of cross infection and protection of dentists and other HCW from COVID-19 and have drafted a paper summarising the evidence.
PVP-I has a better anti-viral activity than other antiseptics such as chlorhexidine,
Elsewhere we describe similar protocols for treating known COVID-19+ patients and the HCW looking after them.
Step 1 – A 0·5% PVP-I solution (standard aqueous PVP-I antiseptic solution diluted 1:20 with water) is administered in a dose of 0·3 ml into each nostril, preferably using an atomising device (two sprays for average device) or if not from a syringe.
Step 2 – 9 ml of the 0.5% solution is then introduced into the oral cavity and used as a mouthwash. Distribute throughout the oral cavity for 30 seconds and then gently gargle at the back of the throat for another 30 seconds before spitting out.
We propose the use of PVP-I applied as per this method for all patients requiring dental treatment during the current COVID-19 pandemic, just prior to treatment. To enhance protection, the operating dental surgeon and assistant should both consider self-administering to the same protocol every 2-3 hours while treating patients during the pandemic, up to four times a day, as an adjunct to currently recommended PPE. The application of PVP-I mouthwash and nasal spray in this way should reduce the cross-infection risk and therefore help to protect dentists. The American Dental Association have very recently published interim guidelines for minimising the risk of COVID-19 transmission which includes the use of a pre-operative 0.2% povidone mouthwash.
A more comprehensive summary of the available evidence, safety data and exclusion criteria are available and we would recommend that this is read before using this protocol.


  1. 1.
    To K K-W, Tsang OT-Y, Chik-Yan Yip C 
  2. 2.
    Kirk-Bailey J, Combes J, Sunkaraneni S, Challacombe S. The use of Povidone Iodine nasal spray and mouthwash during the current COVID-19 pandemic for the reduction of cross infection and protection of healthcare workers. (submitted) Last revised 16 April 2020. Available at: 
  3. 3.
    Eggers M, Koburger-Janssen T, Eickmann M, Zorn J. In vitro bactericidal and virucidal efficacy of Povidone-Iodine gargle/mouthwash against respiratory and oral tract pathogens. 
  4. 4.
    Kariwa H, Fujii N, Takashima I. Inactivation of SARS coronavirus by means of povidone-iodine, physical conditions and chemical reagents. 
  5. 5.
    American Dental Association (ADA) Interim Guidance for Minimizing Risk of COVID-19 Transmission 2020. Available at: 
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Author information


****RISKS: 1 report of Cardiovascular collapse in 2011:

Case Reports


Cardiovascular Collapse Following Povidone-Iodine Wash


Free article


We present a case study of a severe episode of iodine toxicity following povidone-iodine wash with clinical manifestations of cardiovascular collapse, metabolic acidosis, renal failure and seizures. Povidone-iodine has been used as a medical antiseptic and disinfectant since 1952 Iodine toxicity secondary to povidone-iodine use is rare. Iodine toxicity is difficult to diagnose and the diagnosis is made by a high index of suspicion. Toxicity due to iodine correlates with serum and urine iodine levels. Treatment of iodine toxicity is supportive. A review of literature relating to the components of povidone-iodine, iodine metabolism, its manifestations and management of iodine toxicity secondary to povidone-iodine is also presented. An Ovid-Medline search from 1950 to 2009 revealed 1236 articles on the clinical manifestations of povidone-iodine usage but no article on iodine toxicity relating to povidone-iodine based on the following search criteria: povidone-iodine and/or iodine toxicity secondary to povidone-iodine (limited to English language, review articles, full text and human patients).


Published online 2018 Apr 9. 

PMCID: PMC5986684

PMID: 29633177

In Vitro Bactericidal and Virucidal Efficacy of Povidone-Iodine Gargle/Mouthwash Against Respiratory and Oral Tract Pathogens

*****Of note, some articles have stated Povidone Iodine combined with 70 % Alcohol works better than either alone. 

Combination povidone-iodine and alcohol formulations more effective, more convenient versus formulations containing either iodine or alcohol alone: A review of the literature

  • August 2005

  • **++
  • 30 second gargle 
  • 60 second gargle:
    Another article from NYT is very interesting: April 14, 2020:

    Gargling for Coronavirus? What Science Can Tell Us

    There is no firm proof that gargling prevents respiratory infections caused by coronavirus — or any virus or bacteria. But there’s also little downside.

    By Neal Naito, M.D.

    • Published March 29, 2020Updated April 14, 2020

    As Americans search for ways to fight the spread of the coronavirus, one popular topic that has generated interest on the internet is gargling. What’s behind the gargling claim, and is there any medical proof that gargling may help to fight coronavirus or other respiratory infections?

    To date, as with many things in medicine, there has been no “gold standard” large-scale randomized controlled trial to confirm the effectiveness of gargling with salt water, vinegar or any other oral solutions to prevent upper and lower respiratory infections caused by coronavirus or any other virus or bacteria. Smaller studies have shown that mouthwash and various other liquids commonly used to gargle can kill microbes, but whether gargling actually prevents or treats disease has not been proven in rigorous trials.

    Still, gargling is a common hygiene measure in many countries. In East Asia, particularly in Japan, gargling is strongly encouraged by the national government, along with other practices like hand-washing, wearing face masks and social distancing, as a matter of routine hygiene during the regular cold and flu season. (Not everyone, though, can gargle effectively, including some people with neck pain, stroke or dementia, as well as children generally under the age of 8.) Most of the early studies suggesting that gargling may help to prevent and treat upper and lower respiratory infections, not surprisingly, come from Japan.

    The most intriguing findings center on the use of an over-the-counter povidone-iodine oral gargle solution, which has been commonly used for decades by people in Japan and elsewhere to treat a sore throat. In a small Japanese experimental study from 2002, 23 patients with chronic respiratory disease gargled four or more times a day with a povidone-iodine solution. Researchers found that, compared to the number of acute respiratory infections before the group started gargling, regular gargling for several months to two years with the povidone-iodine solution led to an approximate 50 percent reduction in the incidence of acute respiratory infections. Gargling with the solution led to a reduction in infections caused by some fairly virulent bacteria, among them Pseudomonas, Staph (including MRSA) and Haemophilus.

    Laboratory studies have also suggested potential benefits from gargling, though a major limitation of these test-tube studies is that what works in the lab may not translate to health benefits for patients. A recent German lab study sponsored by a manufacturer of povidone-iodine sore throat gargle solution, for example, reported that the solution was shown to eliminate over 99 percent of the coronaviruses that cause SARS and MERS (very close cousins to the current Covid-19). An earlier Japanese lab study revealed that povidone-iodine products outperformed other common antiseptics such as chlorhexidine gluconate and benzalkonium chloride in inactivating many other common problematic viruses, such as coxsackie, rhinovirus, adenovirus, rotavirus, influenza, to name a few. Clinical trials in people would be needed to determine the clinical relevance for patients.

    In the United States, povidone-iodine solutions are sold as skin disinfectants, which contain ingredients that can cause serious harm if ingested; preparations that are suitable for gargling are not generally available in this country. It’s critical that people not gargle with skin disinfectant solutions, including those that contain povidone-iodine. In Canada, a povidone-iodine gargle solution is sold under the brand name Betadine. Some people are allergic to iodine, however, and iodine can cause problems in patients with thyroid problems.

    There is less evidence for the potential antimicrobial benefits of other gargle solutions. Listerine antiseptic, for example, has been shown to have antiviral activity in laboratory test-tube studies against some viruses that had been exposed for at least 30 seconds, though studies have not looked at coronavirus.

    A recent intriguing clinical study from England involving 66 patients suggested that using a homemade hypertonic saline solution for nasal irrigation and gargling significantly reduced the incidence of flu and colds. (Some common colds are caused by coronaviruses, though they are far less dangerous than the strain of coronavirus that is currently circulating.) While nasal irrigation requires a sterile preparation, gargling does not. The gargling solution in the study involved a heaping teaspoon of salt in a cup of water to make an approximate 3 percent saline solution, gargled up to six times a day. A follow-up lab study by the same group of investigators discovered a potential mechanism of action of the saline solution, whereby throat cells took up extra chlorine from the saline solution to produce a compound that has known antiviral properties.

    Other small studies have suggested potential beneficial anti-viral activity of gargling with green tea or solutions containing catechins, active ingredients of green tea, or with  apple cider vinegar. These studies, however, were done in the laboratory, so have unknown clinical relevance for patients, and none looked at coronavirus specifically. One study even suggested that gargling with tap water alone may even be helpful in reducing the incidence of upper respiratory infections in a healthy population, although a later study did not confirm this finding.

    Over all, looking at gargling from a risk-benefit ratio perspective, there seems to be little downside to frequent gargling. It’s a low-cost intervention, and may help to treat a sore throat. Whether gargling will actually fight off colds or flu, however, let alone the more serious coronavirus that is currently circulating, remains indeterminate as the current evidence base is limited.

    Neal Naito, M.D., M.P.H., a former director of public health for the U.S. Navy, is a private practice health care consultant living in Maryland.

    More references: 
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