HomeHealthMedicineThe science behind Covid-19 Nasal sprays

The science behind Covid-19 Nasal sprays

Healthcare worker wearing personal protective equipment (PPE) collects samples for a nasal swab for the public. Viral blockade is a simple premise based on blocking SARS-CoV-2. In other words, if something gets in the way, the virus can’t attach to a cell and infect you. Image for representation. | Photo Credit: Ramalingam Jothi B

We have vaccines to boost our immune response against SARS-CoV-2, the virus that causes COVID. We have medicines you can use at home (and in the hospital) to treat COVID. Now researchers are trying something new.

They want to develop drugs that prevent the virus from entering the body. That includes nasal sprays that prevent the virus from attaching to cells in the nose.

Other researchers are looking at the potential of nasal sprays to prevent the virus from multiplying in the nose, or to make the nose a hostile place to enter the body.

Here’s what science is working on and what we can expect next.

How can we block the virus?

“Viral blockade”, as the name suggests, is a simple premise based on blocking SARS-CoV-2. In other words, if something gets in the way, the virus can’t attach to a cell and infect you.

Since SARS-CoV-2 is a respiratory virus, it makes sense to administer these types of drugs where the virus mainly enters the body – through the nose, in a nasal spray.

There are several groups around the world working on this concept. Some research is still being done in the lab. Some agents have moved on to preliminary human trials. None are yet available for widespread use.


Heparin is a common drug that has been used for decades to thin the blood. Studies in mice show that when heparin is administered through the nose, it is safe and effective at preventing the virus from binding to nasal cells. Researchers believe that heparin binds to the virus itself and prevents the virus from attaching to the cells it is trying to infect.

Also read | Nasal dose: On nasal COVID-19 vaccine

In Victoria, a clinical trial is being conducted in collaboration between multiple research centers in Melbourne and the University of Oxford.


Covixyl-V (ethyl lauroyl arginine hydrochloride) is another nasal spray in development. It aims to prevent COVID by blocking or modifying the cell surface to prevent the virus from infecting.

This compound has been studied for use in a variety of viral infections, and early studies in cells and small animals have shown that it can prevent the attachment of SARS-CoV-2 and reduce the overall viral load.

Iota carrageenan

This molecule, which is extracted from seaweed, works by blocking the entry of viruses into airway cells.

A study of about 400 healthcare professionals suggests that a nasal spray can reduce the incidence of COVID by as much as 80 percent.


This is an engineered antibody that binds to SARS-CoV-2, preventing the virus from attaching to cells in the nose.

A nasal spray and oral (mouth) spray are in a clinical trial to assess safety.

Cold atmospheric plasma

This is a gas that contains charged particles. In cold temperatures, it can change the surface of a cell.

Also read | Time to relax standards: on COVID-19 restrictions

A lab study shows that the gas changes the expression of receptors on the skin that would allow the virus to attach normally. This results in less SARS-CoV-2 attachment and infection. Scientists now think this technology could be adapted to a nasal spray to prevent SARS-CoV-2 infection.

How can we prevent the virus from multiplying?

Another tactic is developing nasal sprays that prevent the virus from multiplying in the nose.

Researchers design genetic fragments that bind to the viral RNA. These fragments – also known as ‘locked nucleic acid antisense oligonucleotides’ (or LNA ASOs for short) – throw a proverbial spanner in the works and prevent the virus from multiplying.

An aerosol spray of these genetic fragments into the nose reduced virus replication in the nose and prevented disease in small animals.

How can we change the nose?

A third strategy is to change the environment of the nose to make it less hospitable to the virus.

This may be by using a nasal spray to change the moisture level (using saline), changing the pH (making the nose more acidic or alkaline), or adding a virucidal agent (iodine). Saline solution can reduce the amount of SARS-CoV-2 in the nose simply by flushing out the virus. One study has even shown that saline nasal irrigation can reduce the severity of COVID disease. But we need further research on saline sprays.

An Australian-led study found that an iodine-based nasal spray reduced the viral load in the nose. Further clinical trials are planned.

One study used a test spray containing ingredients such as eucalyptus and clove oil, potassium chloride and glycerol. The goal was to kill the virus and change the acidity of the nose to prevent the virus from attaching.

This new formulation has been tested in the lab and clinical trial showing that it is safe and reduces the infection rate from about 34 percent to 13 percent compared to placebo controls.

Barriers ahead

Despite promising data so far on nasal sprays for COVID, one of the main barriers is keeping the sprays in the nose. To remedy this, most sprays require several applications per day, sometimes every few hours.

So based on what we know so far, nasal sprays won’t beat COVID on their own. But if they are shown to be safe, effective and approved by the regulatory authorities in clinical trials, they could be another tool to help prevent this.

By Lara Herrero, research leader in virology and infectious diseases, Griffith University (The Conversation)

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