The iodine does help but the salt itself has anti-inflammatory and anti microbial effects. Salt draws fluid from swollen tissues and it is also converted into hypochlorous acid, which is lethal to nearly all microbial pathogens but harmless to the human body.

Iodized salt loses iodine to oxidation and sublimation, so even the minimal amount of iodine added is not always guaranteed. The minimal amount added is only intended to maintain basic thyroid function, similar to the vitamin d added to milk may only prevent rickets. It’s not enough to enhance immune function or fight infection.