It starts as an innocuous tickle in the back of the throat, but before long, there's throat strain, unearthly hacking, and then the sweat. No, we aren't talking about demon possession — we're talking about a cough. A terrible, awful, no-good cough. And when it comes down to it, there are few things more annoying and uncomfortable than that. The occasional cough is totally normal, but a persistent cough can indicate medical problems. Specifically, there are two types of coughs to be aware of.