Antimicrobial mouthrinses and nasal sprays to protect healthcare workers and patients at risk of COVID-19

Cochrane Oral Health and Cochrane ENT have co-published three new reviews looking at antimicrobial mouthrinses and nasal sprays to protect healthcare workers and patients from COVID-19 infection.

COVID‐19 is an infectious disease caused by the SARS‐CoV‐2 virus. Most people infected with COVID‐19 develop a mild to moderate respiratory illness, and some may have no symptoms (asymptomatic infection). Others experience severe symptoms and need specialist treatment and intensive care.

COVID‐19 spreads from person to person primarily through droplets that are produced when an infected person coughs, sneezes or talks. A person can also become infected by touching a surface or object that has viral droplets on it, and then touching their own mouth or nose.

Risk of infection may be particularly high when healthcare workers undertake 'aerosol‐generating procedures', which are medical procedures that cause the patient to produce many small droplets. For example, people who have surgery under general anaesthesia, or people with a lung disease that makes breathing difficult (such as pneumonia), may need to be placed on a ventilator (artificial breathing machine) to help them breathe. This requires a healthcare worker to insert a tube through the patient's mouth, into their airway – a procedure during which many small droplets are likely to be produced by the patient. Similar droplets can be produced during routine dental procedures, such as drilling or scaling of teeth.

Antimicrobial mouthwash and nasal spray are liquids that kill or stop the growth of micro‐organisms such as viruses or bacteria. Administering antimicrobial mouthwash (to rinse the mouth) or nasal spray (sprayed into the nose) to people with COVID‐19 might help them fight the infection and prevent them from infecting the healthcare workers who treat them. It may also protect healthcare workers if they use an antimicrobial mouthwash or nasal spray, particularly before undertaking aerosol-generating procedures. 

As with any medical treatment, antimicrobial mouthwash and nasal spray have potential risks as well as benefits. It is possible that using mouthwash or nasal spray could cause a variety of unwanted (adverse) effects, including irritation, allergic reactions or loss of smell. It may also remove micro‐organisms from the mouth or nose that are useful for protecting the body against infection.

How did we search for evidence?

Our team of researchers searched the medical literature for studies that compared the effects of any antimicrobial mouthwash or nasal spray administered to patients or healthcare workers against no treatment, water, or a salt solution.

What do the three reviews look at?

The three reviews look at different aspects of this question.

1. Antimicrobial mouthwashes (gargling) and nasal sprays administered to patients with suspected or confirmed COVID‐19 infection to improve patient outcomes and to protect healthcare workers treating them

This review aimed to assess the benefits and risks for patients and healthcare workers of administering antimicrobial mouthwashes and nasal sprays to patients with COVID‐19. In particular, we wanted to investigate the effects of patient use of antimicrobial mouthwashes and nasal sprays on:

‐ patient deaths and healthcare needs – including the need for hospitalisation, artificial breathing support, dialysis or haemofiltration (treatments required when the kidneys do not work properly);

‐ new COVID‐19 infections of healthcare workers;

‐ important adverse effects such as loss of smell;

‐ change in patients' COVID‐19 viral load (the amount of virus in an infected person’s blood); and

‐ the viral load of droplets produced by patients.

What did we find?

We found no completed studies to include in this review.

We found 16 studies currently in progress that aim to enrol nearly 1250 participants. These studies are investigating a range of mouthwashes and nasal sprays.

Fourteen of the studies are randomised controlled trials (clinical, real‐life studies where people are randomly put into one of two or more treatment groups). This type of study provides the most robust evidence about the effects of a treatment.

There is currently no evidence relating to the benefits and risks of patients with COVID‐19 using antimicrobial mouthwashes or nasal sprays.

It is important that future studies collect and analyse information about adverse events. Few of the ongoing studies we identified specifically state that they will investigate these. If future studies show a beneficial effect of mouthwashes and nasal sprays, it may not be a large effect (very few health interventions have large and dramatic effect sizes). It will only be possible to weigh up potentially small benefits against risks if any adverse events that occur are reported in studies.

2. Antimicrobial mouthwashes (gargling) and nasal sprays to protect healthcare workers when undertaking aerosol‐generating procedures (AGPs) on patients without suspected or confirmed COVID‐19 infection

This review looked at the benefits and risks of self‐administration of antimicrobial mouthwashes and nasal sprays by patients without a known or suspected COVID‐19 infection, or the healthcare workers who treat them with aerosol‐generating procedures, by reviewing the research evidence.

What did we find?

We found no completed, or ongoing, studies to include in this review.

There is currently no evidence relating to the benefits and risks of healthcare workers' or patients' use of antimicrobial mouthwashes or nasal sprays to protect healthcare workers who undertake aerosol‐generating procedures on patients without a known or suspected COVID‐19 infection.

We need studies to be conducted so that we can answer this important clinical question.

3. Use of antimicrobial mouthwashes (gargling) and nasal sprays by healthcare workers to protect them when treating patients with suspected or confirmed COVID‐19 infection

We also reviewed the research evidence on the benefits and risks of self‐administered antimicrobial mouthwashes and nasal sprays for healthcare workers treating patients with COVID‐19.

There is currently no evidence relating to the benefits and risks of healthcare workers' use of antimicrobial mouthwashes or nasal sprays to protect themselves when they treat people with COVID‐19.

What did we find?

Two randomised controlled trials and one non‐randomised study are underway. Once these studies are completed, we will be able to analyse them and include their findings in an updated version of this review.

Only one of the ongoing studies we identified specifically states that it will investigate adverse events.

Conclusion

We don't yet know the benefits and risks of antimicrobial mouthwashes and nasal sprays on mitigating the risk of COVID-19 infection for healthcare workers and patients. However, some studies are underway and there should be evidence available when these reviews are updated.