More specifically, does gargling help prevent sickness when a person feels the early-stages of being sick? (That slight feeling of rawness in one's throat, for example, or a light, abnormal fatigue).
A friend of mine says that gargling during this stage has worked wonders to prevent oncoming sickness. The argument made is that one absorbs the offending bacteria/viruses via the respiratory tract—and gargling with an antiseptic kills off otherwise sickness-causing pathogens. For example, if wearing a mask helps prevent sickness by blocking pathogens from the throat, why wouldn't using an anti-septic on the throat directly similarly prevent sickness?
I think this is a biological oversimplification. I claim that, by the time a person feels any symptoms, said person is already sick and gargling won't help prevent further sickness.
This study claims that gargling with water as a preventative measure (i.e. - before feeling any rawness, irritation, inflammation, or fatigue) reduces the occurrence of respiratory tract infections. While I don't think it's quite relevant in this question, it's the most related thing I could find.
A somewhat tangential point: We both agree that, if there's some placebo effect going on that increases the chances of fast recovery after gargling, then gargle all day!