I carry it with me in my bathroom kit, and I take it whenever I feel a cold coming on away from home. In each case, the symptoms have gone away. That could be because I believe it will make them go away, or it could be because it really works, or it could be coincidence.

I happen to like the taste, so I don't mind lining the pockets of Walgreens and the drug's maker, on the off chance that it helps.

I think the same placebo effect applies to most drugs: if you believe they will help you, they do.