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I'm seeing different approaches to try protect/alleviate against airborne viruses (e.g. HRV). Let's take some examples:

  • Enzymatica ColdZyme - oral spray
  • P&G Vicks First Defense - nasal spray
  • Taffix - nasal spray

They all claim they stop cold viruses (and more generically airborne viruses) from spreading if used within first hours/day from the symptoms.

Note: there are some claims they can also help against SARS-CoV-2, but this is not the goal of this discussion

As far as I understand, they are acting at different layers:

  • Vicks and Taffix are trying to shield the nasal cavity as it's considered the first body entrypoint
  • ColdZyme shields the oral cavity as they claim that once the virus enters through the nasal cavity, it will be moved from the nasal cavity to the throat by the action of the cilia

I also hear that there is some research going on about SARS-CoV-2 vaccines through nasal spray, which makes me think that nasal cavity protection is the common used approach.

If so, why Enzymatica decided to go through the route of oral cavity protection? Wouldn't be a much less effective scenario as the virus already started its replication in the nasal cavity and it might be already late?

Though on the other hand, by protecting only the nasal cavity, wouldn't be the mouth the other main entrypoint for airborne viruses, which would be left unprotected?

I'm trying to understand the reasons behind choosing one approach instead of another for protecting again the same viruses family.

Perhaps the nasal cavity is by far the biggest risk and only a small percentage of infections (SARS-CoV-2 included) happen by "mouth"/oral cavity?

Many thanks!

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I can't find any evidence that the oral sprays you list work. The ColdZyme website, for example, lists exactly zero studies, and specifically disclaims being a medicine. Taffix claims that a number of studies have been done, but the only in vivo study was very low quality, being an unblinded study.

In short, these give strong evidence of being "snake oil", and thus any design decision should be assumed to be driven by marketing purposes, not medical purposes.

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I agree with Mark, administration route probably doesn't matter because none of these were shown to work.

ColdZyme has an open-label trial but which found no reduction in incidence, and only a very modest reduction in symptom duration. They do mention and even have more recent in vitro trials, but those results insofar don't hold in vivo for reasons that they don't really discuss (the enzyme gets cleared too quickly in vivo maybe?)

P&G got spanked by the UK regulator for misleading advertisement, despite having had a similar trial [which is not clear if it was published somewhere or just provided to the regulator upon complaint.] Tthe regulator decided that P&G could not continue to claim what they did.

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A relevant, unique research paper I found with particular relevance for COVID-19: Hypothesis: Nasal vs. oral inhalation accounts for the severity of COVID-19. People who lose their sense of smell apparently generally experience milder cases than those who do not. This paper theorizes that when a higher percentage of coronavirus particles enter through the nose, more become lodged close to entry, rather than reaching the lungs, trapping the pathogens in a less vulnerable part of the body.

I imagine having infection initially build up in the nasal area also gives the body more lead time to build a strong immune response and produce antibodies before a higher load of coronaviruses possibly reaching the lungs.

If the lungs are the site with most severe vulnerability, it would seem that shielding infection through the mouth could possibly be a higher priority area to focus on, if indeed its natural barriers are being less effective at inhibiting infectiousness of SARS-CoV-2 in the body.

For minimizing risks of infection with COVID-19, an interesting combined approach using both a nasal spray (Snoot) in conjunction with an oral rinse (DioxiRinse) has been proposed in one research paper: Acidified sodium chlorite solution: A potential prophylaxis to mitigate impact of multiple exposures to COVID-19 in frontline health-care providers. The acidified sodium chlorite products mentioned produce chlorine dioxide, which has rapid effectiveness on pathogens even when used at low levels that have minimal impact on the human body.

Various dental rinses have shown high effectiveness SARS-CoV-2 in vitro. A trial is scheduled to begin specifically testing four mouthwashes for their potential to help with COVID-19 contagion control and possibly reduction of symptoms: Antiseptic Mouthwash / Pre-Procedural Rinse on SARS-CoV-2 Load (COVID-19).

The news article "What those studies on mouthwash and coronaviruses actually mean" cautions that findings we have to-date should be evaluated carefully.

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