Iodine mouthwash could protect against Covid-19 and reduce the viral load of infected patients because it has 'significant' virus-killing ability when used on sister viruses SARS and MERS, scientists claim

Iodine mouthwash could destroy the coronavirus and prevent Covid-19 or reduce its effects if someone is already sick, scientists have claimed. 

Researchers said that specific types of mouthwash - made with the chemicals povidone and iodine - can have 'significant virucidal activity'.

Testing on a small group of patients with Covid-19, they found that using the mouthwash reduced the number of viruses that were in their saliva.

Lower viral loads - the number of viruses circulating through the body - have been linked to milder symptoms and faster recovery.

Scientists noted that iodine mouthwashes had proved very effective against the diseases SARS and MERS, which are very similar to Covid-19, so tested them on coronavirus patients.

Although they only tested it on four people, they said the results were promising and that the mouthwash could be used both for patients and uninfected people. They called for a bigger study to be done to test their theory.

Iodine mouthwash is stronger than popular shop-bought products such as Listerine or Colgate, which typically don't contain the antiseptic chemical - it is more commonly used by dentists. One brand that contains iodine is Betadine.

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Scientists say medical-grade mouthwashes - not commercial ones - could kill the coronavirus (stock image)

Writing in the journal Oral Diseases, researchers led by the University of Santiago de Compostela in Spain said: 'Results suggest that a PVP-I rinse [mouthwash] could reduce the saliva viral load of SARS-CoV-2 in patients with higher viral loads. 

'Therefore, routine administration of PVP-I would be primarily indicated for symptomatic patients infected with SARS-CoV-2, especially during the first week after symptom onset, which is when viral charges in the saliva are highest.

'Asymptomatic patients usually have low viral loads, but those who end up developing symptoms have substantially greater viral loads even during the presymptomatic phase; accordingly, the application of PVP-I for the general population could be considered as a supplementary prevention measure'.

The Vigo team tested the effects of the mouthwash on four people who already had Covid-19.

They had been inspired by earlier studies which showed the povidone and iodine mix was very effective at killing SARS and MERS viruses.

Those are both coronaviruses and genetically extremely similar to SARS-CoV-2, which causes Covid-19. 

Iodine is a strong antiseptic and is used in hospitals to sterilise wounds and to clean people's skin during surgery so they don't get infections. 

It is able to kill a huge variety of bacteria, viruses and fungi. 

The Spanish study found that the viral load of coronavirus in each of the patients' saliva tumbled after they were given the mouthwash. 

Viral load is a measure of how many of the coronaviruses somebody has in their body, and is thought to be an indicator of how seriously ill they are or could become.

Other things that may affect it include the way someone was infected.

Someone who breathes in the cough of a hospitalised patient - who have been found to have generally larger viral loads - is likely to have a more severe infection than someone who gets fewer viruses by catching them from a handrail that was touched by a patient without any symptoms.

Past studies have suggested that a lower viral load is linked to less severe symptoms and therefore a lower risk of death from Covid-19.

The researchers said mouthwash, if effective, could be a cheap way to try and protect people from serious illness.

'Given that a PVP-I rinse is a simple, inexpensive and practically innocuous intervention,' Professor Pedro Diz Dios and colleagues wrote, 'we consider that the encouraging results of the present study justify implementing a clinical trial to confirm its efficacy.' 

Professor Dios and his team called for another, larger study to be done to test their theory and see if mouthwash could help.

The paper adds to past research which has suggested mouthwash has protective effects in other ways.

A team of international researchers said in May that mouthwash may be able to destroy the outermost layer or 'envelope' of the virus, preventing its replication in the mouth and throat.

Coronaviruses belong to the class of 'enveloped viruses', meaning they are covered by a fatty layer that is vulnerable to certain chemicals. 

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The researchers found that the viral load of the coronavirus patients fell within hours after they rinsed their mouths out with the mouthwash

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Iodine mouthwashes are generally not the same as those bought in supermarkets - popular brand Listerine has had to post a warning on its website that its product does not prevent Covid-19

The study authors do not say that current commercially-available mouthwash prevents COVID-19, but that further research into mouthwash chemicals could be beneficial. 

Writing in the journal Function, the study authors, led by Cardiff University, say oral rinses are an ‘under-researched area of major clinical need’.

The team is backed by virologists, lipid specialists and healthcare experts from Cardiff University’s School of Medicine, along with the universities of Nottingham, Colorado, Ottawa, Barcelona and Cambridge’s Babraham Institute.

'Safe use of mouthwash – as in gargling – has so far not been considered by public health bodies in the UK,' said lead author Professor O’Donnell, co-director of Cardiff University’s Systems Immunity Research Institute.

'In test tube experiments and limited clinical studies, some mouthwashes contain enough of known virucidal ingredients to effectively target lipids in similar enveloped viruses.

'What we don’t know yet is whether existing mouthwashes are active against the lipid membrane of SARS-CoV-2.

'Our review of the literature suggests that research is needed as a matter of urgency to determine its potential for use against this new virus.'

'This is an under-researched area of major clinical need – and we hope that research projects will be quickly mobilised to further evaluate this.' 

The ingredients of dental mouthwashes, including chlorhexidine, cetylpyridinium chloride, hydrogen peroxide and povidone-iodine, all have the potential to prevent infection and several ‘deserve clinical evaluation’, according to the researchers.