In my experience, it certainly takes the symptoms away, but the illness might last longer, since you're stressing your body.
I smoke if I'm nauseous, otherwise I just down a bottle of Robitussin. Don't get me wrong though, it has the same problem I stated above.
You could smoke during the entire time until your body fights it off.. you'd be sick for longer, but the only "side effect" would be that you're high.