There is some concern about gargling over the counter Betadine. The concern is that it contains lye which is sodium hydroxide. Sodium hydroxide can be dangerous to the eye if splashed into the eye in high concentrations (ref 1). However, in very low amounts it appears to be very safe for ocular tissues.
Povidone iodine-containing sodium hydroxide, has been used for years in various preparations as “sterile povidone-iodine eye drops” which are used before most eye surgeries (see photos below which is what many surgeons use as an eye drop before eye surgery and Ref 2).
Aside from allergy to iodine, these drops seem to be very safe to use before eye surgery.
Note that the inactive ingredients in both Over the counter Betadine and Minims Povidone Iodine 5% sterile eye drops, solution are the same.
The key issue is to be sure to dilute 10% povidone iodine to %5 before using on eye or using in nose, gargling, or for other mucous membranes. Avoid inhalation or aspiration.
More information below:
Over the counter Betadine:
BETADINE* 5% Sterile Ophthalmic Prep Solution contains 5% povidone-iodine (0.5% available iodine) as a sterile dark brown solution stabilized by glycerin. Inactive Ingredients: purified water, citric acid, glycerin, nonoxynol-9, sodium chloride, sodium hydroxide, and dibasic sodium phosphate.
Minims Povidone Iodine 5% sterile eye drops, solution
Minims Povidone Iodine 5% w/v eye drops, solution