I ve had cold symtoms for 5 or 6 days, starting with a sore throat , then chest congestion , sinus congestion, headaches, etc. Suddenly last night at dinner, I began to experience an odd taste in my mouth. I thought perhaps a chemical had not been rinsed from my drinking glass, however this has persisted. Now, the odd taste won t go away, and everything now smells the same way. The taste is horrible and persistent. I had been taking Mucinex DM. Is there a chance this is a side effect of that medication, or perhaps a symptom of a sinus infection?