Mouthwash, Nasal Sprays and Covid-19

There has been a lot of speculation about whether gargling with mouthwash or using a simple nasal spray, can help to reduce your chances of being infected by Sars-CoV-2. A relatively large study in Cardiff looked at the impact of 7 common mouthwashes on the viability of the virus in in vitro laboratory settings (https://www.health.com/condition/infectious-diseases/coronavirus/does-mouthwash-kill-covid-19). They found that 2 Dentyl products (Dual Action and Fresh Protect), both containing cetylpyridinium chloride, and Listerine Advanced mouthwash, containing ethyl lauroyl arginate, "eradicated the virus completely after a 30 second treatment". Although this sounds good (and is possibly worth investigating further), there is currently no evidence that the effects would be replicated by real humans using the mouthwash (in vivo). Interestingly, given the early obsession in the pandemic with hand sanitiser (where the active ingredient is alcohol), mouthwashes containing ethanol alone, appeared to have no effect on the virus. It has been noted that mouthwash can kill a lot of things. That doesn't mean, however, it will protect you from a virus, largely transmitted by a combination of breathing in air-borne material and ingesting it from your fingers. Similar speculation about efficacy against Covid-19 has concerned Vick's First Defence nasal spray (marketed as a protection against infection by the Common cold virus). Again, the evidence is very limited for this or any other nasal sprays. I'm pretty cerain that cheap washing up liquid will also eradicate the virus completely after a 30 second treatment in laboratory cultures. I would not, however, want to gargle with it or squirt it up my nose! Having said all that, keeping yourself and your environments as sanitised as reasonably possible can't be a bad thing.