Hello I had very bad cough for the whole week and I decided to take mucinex 1200mg, it helps to loosen mucus. I have been taken it once a day for 3 days already. And for the past 2 days I am having very bad rash, on my face, back, shoulders, legs and my hands were swollen this morning. So I read what it says on the pack: stop using and ask doctor if cough lasts more than 7 days, comes back, or occurs with fever, rash or headache. This could be signs of a serious illness. after this I don t know how to react on this. What serious illness can it be?