From FAQ flccc.net

Can you explain more about oral rinsing and nasal sprays?

Gargling and rinsing (not swallowing, drinking) mouthwash solutions and using nasal sprays or nasal rinses are done to reduce the viral load in the nose and throat which in turn reduce the symptoms and severity of disease. This is likely more important with the Delta variant given it replicates faster and creates higher viral loads. Povidone iodine nose spray/drops should not be used longer than 5 days in pregnancy.

What mouthwash? Any mouthwash containing cetylpyridinium chloride (CPC) has broad antimicrobial properties and is effective in controlling gingivitis and gingival plaque. Examples of mouthwashes with CPC are Scope™, ACT™, and Crest™.

What nasal spray or rinse? Use 1% povidone-iodine commercial nasal spray as per instructions 2-3 x daily. If 1% product is not available, dilute the more widely available 10% solution and apply 4-5 drops to each nostril 4-5x daily for post-exposure prevention and the early symptomatic period.

To make 1% povidone/iodine concentrated solution from 10% povidone/iodine solution, IT MUST BE DILUTED FIRST. One dilution method is as follows:

  First pour 1½ tablespoons (25 ml) of 10% povidone/iodine solution into a nasal irrigation bottle of 250 mL
  Then fill to top with distilled, sterile or previously boiled water
  Tilt head back, apply 4-5 drops to each nostril. Keep tilted for a few minutes, let drain. No more than 5 days in pregnancy.