Vocalzones enable you to sing when you probably shouldn't. For an emergency if you have to, use them but be aware that you can be damaging your vocal chords. The important thing is to keep your vocal chords hydrated. Water, weak tea or weak fruit juice do this. Alcohol, black coffee and throat lozenges don't.

Inhaling steam is a good way of hydrating vocal chords directly. Drinking liquid doesn't touch the vocal chords themselves because their purpose is to close the lungs off from liquid we drink. A voice therapist I heard said that most of her patients were untrained semi professional singers who belted it out in smoky pubs and clubs and used all sorts of things to keep singing when they should be resting.

I had a friend who had a persistent cough who turned out to be allergic to his dog. Worth a thought.