OTC nasal sprays have been used for years by dentists and others, but like everything else these days, are contested, https://news.ycombinator.com/item?id=29620297

If one is concerned about possibly-false positives in a test, there may be value in OTC nasal treatments.

> The Response we filed also includes a new in vitro study done at Utah State University’s Institute for Antiviral Research. This new in vitro study found that the components in Xlear were significantly more effective antivirals against the Delta strain of COVID-19 than Remdesivir, the Government-approved antiviral medicine. Ironically, the Government alleges it is Xlear that has misled the public.